Berthing Structures

Berthing Structures

R. Sundaravadivelu 1

Chapter 6

BERTHING STRUCTURES

R. SUNDARAVADIVELUProfessor

Dept. of Ocean EngineeringIndian Institute of Technology

ChennaiIndia

6.1 INTRODUCTION

The berthing structures are constructed for berthing and mooring of vessels to enableloading and unloading of cargo and for embarking and disembarking of passengers,vehicles. The design of berthing structures depends on various factors. However, thevessel characteristics govern the design of berthing structures.

The various structures constructed along the coast can be classified as Port and HarbourStructures, Coastal Protection Structures, Sea water Intake Structures and Effluentdischarge structures. Port and harbor structures are constructed along the coast to provideberthing facilities to ships for loading and unloading of cargo or for embarking anddisembarking passengers. The different types of berthing structures are given in thissection.

6.2 TYPES OF BERTHING STRUCTURES

Berthing structure is a facility where the vessel may be safely moored. The berthingarrangements can be classified as along side type, open dolphin type or ferry typeas shown in Figure 6.1 (Gaythwaite (1990)).

The berthing structure can also be classified as vertical face type or open type structure.Typical examples are shown in Figure 6.2 (Agerschou et al (1985). In vertical face

Harbour & Coastal Engineering (Indian Scenario) : Vol. I

430

structures, sheet pile wall, block wall, caissons are used, while open type structures arerepresented by open piled construction.

Fig 6.1 Types of Berthing Structures

FERRY (SLIP) TYPE

OPEN DOLPHIN TYPE

FINGER PIER OR DOLPHINS

TRANSFER BRIDGE

GUIDE DOLPHINS

TRESTLE TO SHORE

LOADING PLATFORMMOORING DOLPHIN

BREASTING DOLPHIN

ALONGSIDE TYPE

Berthing Structures


Fig 6.2 Types of Vertical Face Berthing Structures

(a) CAISSON

(c) OPEN PILED STRUCTURES

(b) SHEET PILE WALL


432

The berthing structures can also be classified depending on the type of cargo handled.The Madras Port outer harbour basin has oil berth, ore berth and container berth where oil,ore and containers are handled respectively. The berthing structures can also be classifiedas follows:

(A) GRAVITY STRUCTURES

(i) Masonry wall

(ii) Concrete block walls

(iii) Concrete caissons

(B) FLEXIBLE STRUCTURES

(i) Steel sheet piles - Tie back

- Cantilever

(ii) Diaphragm walls - Cantilever

- Tieback

- Relieving platform

(iii) Jetties - consist Berthing & Mooring Dolphin, Jetty Head & Approach Jetty.

The minimum length of a berthing structure should be sufficient for mooring the longestship expected to arrive. The minimum depth includes a bottom clearance equivalent to10 % of the draught of the largest vessel using the terminal. The top surface of theberthing structure should be built above the highest high water level.

The dimension of the berth as recommended by IS 4651 (Part V) - 1980 is given inAppendix 6.1 for various size of Passenger ships, Freighter, Tankers, Ore Carriers andLarge Fishing Vessels.

6.2.1 Quay or Wharf

Quays are defined as one or more berths, continuously bordering on and it contact with aland or dock area. The inner harbour basin of Madras Port has North, South, East andWest Quays where berthing facilities are provided for number of ships.

Berthing Structures


The quays are constructed as sheet pile wall, diaphragm wall, open piled structure orgravity structure [Quinn (1972) and Bruun (1981)]. Quay is a continuous berth wherefenders and bollards are provided at different points along the berth to facilitate berthing ofships.

Wharf is the same as Quay, constructed as an open structure supported on piles.

6.2.2 Pier or Jetty

A pier or jetty is a structure projecting into water, in a harbour basin. They are also locatedin open water outside actual harbours. A finger jetty will have berths on two sides and abutland over their full width.

A jetty consists of a number of structures such as berthing dolphin, mooring dolphin,loading platform, trestle to shore each of which has special type of functions.

The mooring dolphins pick up the pull from the hawsers. Mooring dolphins for breast linesshall be located at bow and stern at a distance (about the beam of the ship) from the berthline, which will not make the moorings too steep.

The berthing dolphins support fenders which absorb berthing impacts. The berthingdolphins should be placed as wide apart as possible. The distance should neither exceedthe length of the straight side of the smallest vessel nor be less than approximately one-third of the maximum length of the largest vessel.

The loading platforms support special loading or unloading equipment but normally nohorizontal forces apart from wind loads will act on the loading Platforms.

6.2.3 Offshore Berthing Structures

Offshore berthing structures are used for liquid cargo (oil or gas) or for dry cargo, for ironore, coal, sugar, phosphates or grains. The design for offshore berthing structures shouldconsider the following :

a) Single type of cargo

b) Rapid loading and unloading (10,000 T of Iron ore per hour or 60,000 bbl(barrel) of oil per hour)

c) Sufficient storage on shore

d) Open sea and exposed to winds, waves and currents


434

e) Construction practicability

f) DWT of the vessel in the range of 0.1 million T to 0.3 million T

The type of ship loader generally governs the design of offshore berth. The three maintypes of ship loader are (1) Fixed type (2) travelling Gantry type and (3) Slewingtelescopic boom loaders. The fixed loader is used in small ships. The travelling gantryloader is expensive, since the loader is to be supported by a berth which is continuous. Theabove three types of loaders are to be critically evaluated for dry bulk cargo terminals,whereas for liquid cargo, the loading system does not influence the offshore berthingstructure. The approach jetty to the offshore berthing structure is the critical componentand governs the total cost of the facility. The offshore terminal at CAPE Santa Clara in theAtlantic ocean consists of a principal berth to load 2,80,000 DWT ship, moored 7400 mfrom shore. The mooring and berthing force in the offshore berth is to be criticallyevaluated for the safe design of the offshore berthing structure.

6.3 LOADS ON BERTHING STRUCTURES

The berthing structures are designed for the following forces :

(i) Berthing force

(ii) Mooring force

(iii) Dead load

(iv) Live load - Rail - Road - Bulk unloaders - Cranes etc. - UDL due to cargo

(v) Active earth pressure if the berth retains the earth

(vii) Environmental forces - Wind - Wave - Current - Differential water pressure

(viii) Seismic force

(ix) Secondary stresses due to shrinkage, creep, temperature etc.

Berthing Structures


6.3.1 Classification of Loads

The various loads acting on the berthing structures are classified as :

i) Loads from the sea side

ii) Loads from the deck and

iii) Loads from the land side

6.3.1.1 Loads from Seaside

The loads from the sea side include the horizontal forces caused by waves, the forcescaused by berthing and vessel’s pull from bollard. The forces caused by berthing ofvessels are determined from the velocity and angle of approach of the vessels. For thevessels lying at the berth, the forces are determined due to wind, waves and currents on thevessel. The vertical forces from sea side are due to vessels hanging upon the fenderingsystem, vertical component of the forces from bollards etc.

6.3.1.2 Loads from Deck

The important loads from the deck are the vertical loads caused by self weight of the deck,superimposed loads from buildings and handling equipments. Horizontal loads are mostlydue to wind forces on buildings and structures and also due to the breaking force of cranes.

6.3.1.3 Loads from Landside

Horizontal loads are caused from landside due to the earth pressures and differential waterpressure. Vertical loads are caused by the weight of filling and superimposed load onfilling.

6.3.2 Live Loads

6.3.2.1 Vertical Live Loads

Surcharges due to stored and stacked material such as general cargo, bulk cargo, containersand loads from vehicular traffic of all kinds including trucks, trailers, railway cranes,containers handling equipment and construction plant, constitute vertical live loads.


436

6.3.2.2. Truck loading and Uniform loading

The berths shall be generally designed for the truck loading and uniform loading as givenin Table 6.1 (IS 4651 (Part III) - 1974).

Table 6.1 Truck Loading and Uniform Loading

Function of Berth Truck Loading(IRC class)

Uniform Vertical LiveLoading (T/m2)

Passenger berth B 1.0Bulk unloading and loadingberth

A 1 to 1.5

Container berth A or AA or 70 R 3 to 5Cargo berth A or AA or 70 R 2.5 to 3.5Heavy cargo berth A or AA or 70 R 5 or moreSmall boat berth B 0.5Fishing berth B 1.0

6.3.2.3 Crane Loads

Concentrated loads from crane wheels and other specialised mechanical handlingequipment should be considered. An impact of 25 percent shall be added to wheel loads inthe normal design of deck and stringers, 15 percent where two or more cranes act togetherand 15 percent in the design of pile caps and secondary framing members.

6.3.2.4 Railway Loads

Concentrated wheel loads due to locomotive wheels and wagon wheels in accordance withthe specification of the Indian Railways for the type of gauge and service at the locality inquestion. For impact due to trucks and railways one third of the impact factors specified inthe relevant codes may be adopted.

6.3.2.5 Special Loads

Special loads like pipeline loads or conveyor loads or exceptional loads such as surchargesdue to ore stacks, transfer towers, heavy machinery or any other type of heavy lifts shouldbe individually considered.

Berthing Structures


6.3.3 Berthing Load

Berthing Energy : When an approaching vessel strikes a berth, horizontal force acts on theberth. The magnitude of this force depends on the kinetic energy that can be absorbed bythe fendering system. The reaction force for which the berth is to be designed can beobtained and deflection-reaction diagrams of the fendering system chosen. Thesediagrams are obtainable from fender manufacturers. The kinetic energy, E, imparted to afendering system, by a vessel moving with velocity V is given by

semD CxCxC

g2VxW

E2

= (6.1)

where

E = Berthing energy in T- m

WD = Displacement tonnage in T

V = Berthing velocity in m/sec

Cm = Mass coefficient

Ce = Eccentricity coefficient

CS = Softness coefficient

g = Acceleration due to gravity in m/sec2

6.3.3.1 Mass Coefficient

When a vessel approaches a berth and as its motion is suddenly checked, the force ofimpact which the vessel imparts comprises of the weight of the vessel and the effect ofwater moving along with the moving vessel. Such an effect, expressed in terms of weightof water moving with the vessel, is called the additional weight (WA) of the vessel or thehydrodynamic weight of the vessel. Thus the effective weight in berthing is the sum ofdisplacement tonnage of a vessel and its additional weight, which is known as virtualweight (WV) of a vessel.

a. The mass coefficient (Cm) is calculated using the following equation

BD21Cm += (6.2)


438

where

D = Draught of the vessel in m,

B = Beam of the vessel in m.

b. Alternative to (a) in case of a vessel which has a length much greater than its beamor draught or generally for vessels with displacement tonnage greater than 20,000 theadditional weight may be approximated to the weight of a cylindrical column of water ofheight equal to the length of vessel and diameter equal to the draught of vessel, then

D

24

m WLwD

1Cπ

+= (6.3)

where

D = Draught of the vessel in m,

L = Length of the vessel in m

w = Unit weight of water (1.03 T/m2 for sea water)

WD = Displacement tonnage of the vessel in tonnes.

Wv = WD x Cm

6.3.3.2 Eccentricity Coefficient

A vessel generally approaches a berth at an angle, denoted by θ and touches it at a pointeither near the bow or stern of the vessel. In such eccentric cases the vessel imparts arotational force at the moment of contact, and the kinetic energy of the vessel is partiallyexpended in its rotational motion.

a) The eccentricity coefficient (Ce) may then be derived as follows:

2

22

e )r/l(1Sin)r/l(1C

+θ+

= (6.4)

where

l = Distance from the centre of gravity of the vessel to the point of contact projectedalong the water line of the berth in m, and

r = Radius of gyration of rotational radius on the plane of the vessel from its

Berthing Structures


Fig 6.3 Approaching Angle of Vessel with a Berth

Center of gravity in m (Figure 6.3)

b) The approach angle (θ) unless otherwise known with accuracy should be taken as 10°.For smaller vessels approaching wharf structures, the approach angle should be takenas 20° (Refer Figure 6.3).

BERTHING POINT OF THE VESSEL (l)

ECC

ENTR

ICIT

Y C

OEF

FIC

IEN

T (C

e)

0.6

0.1L0.0

0.2

0.4

0.8

1.0

0.2L 1/4L 0.3L 0.5L0.4L

θ= 10° UNLESS KNOWN ACCURATELY

20° FOR SMALLER VESSEL

G

θ

For θ = 0


440

c) The rotational radius of a vessel may be approximated to L/4 and in normal case thepoint of contact of the berthing vessel with the structure is at a point about L/4 fromthe bow or stern of the vessel which is known as a quarter point contact. If theapproach angle θ is nearly 0° and r = 0.25 L, then Ce = 0.5.

6.3.3.3 Softness Coefficient

This coefficient (Cs) indicates the relation between the rigidity of the vessel and that of thefender, and also the relation between the energy absorbed by the vessel and the fender.Since the ship is relatively rigid compared with the usually yielding fendering systems, avalue of 0.9 is generally applied for this factor, or 0.95 if higher safety margin is thoughtdesirable.

Quinn (1961) has suggested a suitable formula for calculating the berthing energyassuming 50% of the total energy of the berthing vessel to be absorbed by fenders.

= 2mv21

21E (6.5)

where m is the (mass + added mass) of the vessel and v is the berthing velocity.

6.3.4 Mooring Loads

The mooring loads are the lateral loads caused by the mooring lines when they pull theship into or along the dock or hold it against the forces of winds or current.

6.3.4.1. Forces due to Wind

The maximum mooring loads are due to the wind forces on exposed area on the broad sideof the ship in light condition

F = Cw Aw P (6.6)

Where

F = Force due to wind in kg

Cw = Safe factor = 1.3 to 1.6

Aw = Windage area in m2 and

P = Wind pressure in kg/m2 to be taken in accordance with IS : 875-1964

Berthing Structures


The windage area (Aw) can be estimated as follows

Aw = 1.175 Lν (DM - DL) (6.7)where

Lν = Length between perpendicular in m

DM = Moulded depth in m

DL = Average light draft in m.

When the ships are berthed on both sides of a pier, the total wind force acting on the pier,should be increased by 50 percent to allow for wind against the second ship.

Gaythwaite (1990) has suggested the following formulas to calculate windforce in thelongitudinal (Fwx) and lateral (Fwy) force components and a yawing moment (Myw).

Fwx = 0.0034 CDx V2w Ax (6.8)

Fwy = 0.0034 CDy V2w Ay (6.9)

Myw = Fwy LOA Cym (6.10)

Where

Fwx and Fwy = Wind Force along x and y directions in poundsMyw = Yawing Moment in pounds-ftCDxand CDy = Drag Coefficients along x and y directionsVw = Wind speed in KnotsAx and Ay = End-on and Side projected areas of vessel (including the areas

of masts, stacks, rigging, deck cargoes, etc.)LOA = Overall Length of Ship in ft

The hydrodunamic coefficients are the functions of angle of wind approach(θ). The yawmoment is given in terms of the lateral force times the vessel’s length overall (LOA) andCym. The total resultant force for wind from any direction (Fw(θ)) is found from thisequation:

Fw (θ) = 0.0034CD(θ) V2w (Ax cos2 θ + Ay sin2 θ) (6.11)


442

6.3.4.2 Forces due to Current

Pressure due to current will be applied to the area of the vessel below the water line whenfully loaded. It is approximately equal to w v2/2g per square metre of area, where v is thevelocity in m/s and w is the unit weight of water in T/m3. The ship is generally berthedparallel to the current. With strong currents and where berth alignment materially deviatesfrom the direction of the current, the likely force should be calculated by any recognisedmethod and taken into account.

Ship is aligned predominantly in head sea condition with current direction.

Example problem 1:

Calculate the berthing force, and Mooring force due to 30,000 DWT bulk carrierapproaching the berth at Kandla Port with a berthing angle of 10°. The site condition ismoderate wind and swells and the berthing condition is moderate. Use the followinginformations. (Design data)

Length of the berth = 240 m

Width of the berth = 55 m

Top level = + 9.74 m

Dredge level = - 11.10 m

Length of the vessel = 205 m

Width of the vessel = 26.5 m

Draught = 10.70 m

Berthing force

Site conditions : Moderate wind and swells

Berthing condition : Moderate

As per IS 4651 (Part III)-1974 for the above site condition and berthing condition

Berthing velocity (v) = 0.2 m/s

SemD CCCg2VWE

2

=

Berthing Structures


32.1DWTDT

= as per Section 3.1.2 of IS 4651 (Part II)-1974

WD = 1.32 x 30,000 = 39,600 T

D

24

WLWD

1Cmπ

+=

where

w = Unit weight of sea water 1.025 t/m3

Cm =600,39

025.1*205*7.10*1

24π

+

Cm = 1.48

Ce =( )

( )2r

22r

1

sin11

l

+

θ+

l = L/4 = 205/4 = 51.25 m

r = 0.2 L = 0.2 x 205 = 41 m

θ = 10°

Ce =( )

( )2425.51

2241

25.51

1

10sin1

+

+

Ce = 0.41

CS = 0.95 (As per code)

95.0*41.0*48.1*81.9*2

)2.0(*600,39E2

=

E = 46.54 T – m

Ultimate energy = 1.4 x 46.54 = 65.2 T-m


444

Fender details : fender type - cell (from fender manufacture catalogue)

Size of fender – 1600H x 2005D x 1800 P

Berthing force = 100 T

Mooring force

Length between perpendicular (Lp ) = 0.9 L = 0.9 x 205 = 184.5 m

Moulded depth of the ship (Dm ) = 14.3 m

Average light weight draft (DL ) = 10.3 m

Due to Wind

Aw = 1.175 x 184.5 (14.3 - 10.3)

Aw = 867.15 m2

P = 0.06 Vz2 (As per IS 875-1987)

Vz = Vb k1 k2 k3

Vz = Design wind speed at any height

k1 = Probability factor (risk coefficient)

k2 = Terrain, height and structure size factor

k3 = Topography factor

Basic wind speed - 39 m/sec (at Kandla)

Vb = 1.15 x 39 (for offshore area)

= 44.85 m/sec

K1 = 1.08, K2 = 1.05, K3 = 1

Vz = 44.85 x 1.08 x 1.05 x 1 = 50.86 m/s

P = 0.06 x (50.86)2 = 155 Kg/m2

Fw = 1.4 x 867.15 x 155 (as per Equation (6.6))

= 188 T

Berthing Structures


Due to Current

where

g2wvF

2

c = x projected area of ship

w = Unit weight of water in t/m3

v = Current velocity 5 knots

g = Acceleration due to gravity in m/s2

w = 1.025 t/m3 v = 0.5 x 0.505 = 2.525 m/s

g = 9.81 m/s2

T91.947.10*5.26*81.9*2525.2*025.1

F2

c ==

Total force = sqrt(1882 + 952) = 210 T

The total force can be assumed to be equally distributed to four bollards, if the ship ismored to eight bollards. Force on each bollard = 210/4 = 52.5 T

The line pull as per Table 6.2 is 60 T for the 20000 DWT vessels and T for the50000 DWT vessels.

Table 6.2 : Bollard Pulls

Displacement (Tonnes) Line Pull (Tonnes)2,000 10

10,000 3020,000 6050,000 80100,000 100200,000 150

>200,000 200

Hence the mooring pull for 30,000 DWT vessel is 67. However the mooring pull isassumed as 75 T.


446

Fig. 6.4 Differential Water Pressure

6.3.5 Differential Water Pressure

In the case of waterfront structures with backfill, the pressure caused by difference in waterlevels at the fillside and the waterside has to be taken into account in design.The magnitude of this hydrostatic pressure is influenced by the tidal range, free waterfluctuations, the ground water influx, the permeability of the foundation soil and thestructure as well as the efficiency of available backfill drainage.

In the case of good and poor drainage conditions of the backfill the differential waterpressure may be calculated on the guidelines given in Figure 6.4. The average of MLWSand LLW is assumed water level on the sea side for both poor and good drainageconditions. The average of MHW and MLW is assumed as ground water (GW) on the landside for poor drainage condition, while 0.3 m above MLW is assumed a ground water(GW) on the land side for good drainage condition

MHW - MEAN HIGH WATER

MLW - MEAN LOW WATERMLWS - MEAN LOW WATER SPRINGS

GW - GROUND WATERLLW - LOWEST LOW WATER

bLLW

(a) POOR DRAINAGE CONDITION

MHW

MLW

MLWS

b

ASSUMED GW

(b) GOOD DRAINAGE CONDITION

ASSUMED GWMLWMLWS

LLW

FLAP VALVE

a

a

b

b

MHW ELEVATION OF FLAP VALVE BOTTOM

0.3m

Berthing Structures


6.3.6 Seismic Force

The horizontal force caused by earthquakes called seismic force can be calculated usingthe seismic coefficient method given in IS 1893-1984 (10). The horizontal seismicforce(Fh) is given by the following equation

Fh = αh Wm (6.12)

where

αh = Design horizontal seismic coefficient

Wm = Weight of mass under consideration ignoring reduction due to buoyancy of uplift and is equal to the total dead load plus one-half of the live load as per IS 1893 (Part III)-1984.

The design values of horizontal seismic coefficient, in the Seismic Coefficient methodshall be computed as given by the following expression:

αh = βIαo (6.13)

where

β = A coefficient depending upon the soil-foundation system

I = A factor depending upon the importance of the structure

αo = Basic horizontal seismic coefficient based on the zone

β, I and αo can be obtained from IS 1893-1984, depending on type of soil foundation,importance of the structure and the zone in which the structure is located.

6.3.7 Wave Forces

As far as analysis and computation of forces exerted by waves on structures are concerned,there are three distinct types of waves, namely,

1. Non-breaking waves

2. Breaking waves and

3. Broken waves


448

6.3.7.1 Non-breaking Waves

Generally, when the depth of water against the structure is greater than about 11/2 times themaximum expected wave height, non-breaking wave conditions occur.

Forces due to non-breaking waves are essentially hydrostatic. ‘Sainflou Method’ may beused for the determination of pressure due to non-breaking waves.

6.3.7.2 Breaking Waves

Breaking waves cause both static and dynamic pressures. Determination of the designwave for breaking wave conditions may be based on depth of water about seven breakerheights (Hb) seaward of the structure, instead of the water depth at which the structure islocated. The actual pressures caused by a breaking wave is obtained by following themethod suggested by Minikin.

6.3.7.3 Broken Waves

Locations of certain structures like protective structure will be such that waves will breakbefore striking them. In such cases, no exact formulae have been developed so far toevaluate the forces due to broken waves, but only approximate methods based on certainsimplifying assumptions are available.

6.3.7.4 Wave Force on Piles

Wave forces on vertical cylindrical structures, such as piles exerted by non-breaking wavescan be divided into two components;

a. Force due to drag

b. Force due to inertia

A set of generalised graphs which are available in shore protection manual together withthe following formulae may be used to compute these;

FDM = 1/2 CD ρg D H2 KDM (6.14)

FIM = CM ρg4D 2π H KIM (6.15)

FM = φm ρg H2D (6.16)

Berthing Structures


MDM = SD FDM d (6.17)

MIM = SI FIM d (6.18)

Mm = αm ρg CD H2D d (6.19)

HCDCW

D

M= (6.20)

where

FDM = Total drag force on a vertical pile from the sea bottom to the surface crest elevation and this occurs at the crest positions in N

d = Water depth in m

g = Acceleration due to gravity

ρ = Mass density of sea water = (w/g) = 1025.2 kg/m3

D = Diameter of pile in m

H = Wave height in m

KDM = Drag force factor (Figure 6.5)

FIM = Total inertial force on a vertical pile from the seabed to the free surfaceelevation in N

KIM = Inertial force factor (Figure 6.6)

SDM = Drag force moment arm (Figure 6.7)

SIM = Inertia force moment arm (Figure 6.8)

αm,φm = Coefficients read from the Figures 6.9 to 6.16

CD,CM = Drag, Intertia coefficient (Figures 6.17 to 6.18)

FM = Maximum value of the combined drag and inertial force in N

MDM = Moment on pile about bottom associated with maximum drag force in N-m

SD = Effective lever arm for FDM from the bottom of pile in m

MIM = Moment on pile about bottom associated with maximum inertial force in N-m

SD = Effective lever arm for FIM from the bottom of pile in m

MM = Maximum total moment in N-m


450

Fig.

6.5

KD

mve

rsus

Rel

ativ

e D

epth

(d /

gT2 )

Berthing Structures


Fig.

6.6

KIM

vers

us R

elat

ive

Dep

th (d

/ gT

2 )


452

Fig

6.7

SD

Mve

rsus

Rel

ativ

e D

epth

(d/g

T2 )

Berthing Structures


Fig

6.8

SD

Mve

rsus

Rel

ativ

e D

epth

(d/g

T2 )


454

Fig

6.9

Isol

ines

ofφ

mve

rsus

H/g

T2

and

d/g

T2(w

= 0

.05)

Berthing Structures


Fig

6.10

Iso

lines

of

φ mve

rsus

H/g

T2

and

d/gT

2(W

= 0.

1)


456

Fig.

6.11

Iso

lines

ofφ

mvs

H/g

T2

and

d/gT

2(W

= 0

.5)

Berthing Structures


Fig

6.12

Iso

lines

ofφ

mve

rsus

H/g

T2

and

d/gT

2(W

= 1

.0)


458

Fig

6.13

Iso

lines

ofα

mve

rsus

H/g

T2an

d d/

gT2

(W =

0.0

5)

Berthing Structures


Fig

6.14

Is

olin

es o

fαm

vers

us H

/gT

2an

d d/

gT2

(W =

0.1

)


460

Fig

6.15

Isol

ines

ofα

mve

rsus

H/g

T2

and

d/gT

2(W

= 0

.5)

Berthing Structures


Fig.

6.1

6 I

solin

es o

fαm

vers

us H

/gT2

and

d/gT

2(W

= 1

.0)


462

Fig 6.17 Interia and Drag Coefficient for a Fixed Vertical Cylinder

Berthing Structures


Fig 6.18 Drag Coefficient for a Smooth Oscillating Cylinder


464

Example Problem 2 :

A design wave height of (H) 5.0 m and period (T) 10 secs acts on a vertical circular pilewith a diameter (D) of 1 m and depth (d) 8 m. Assume Cm = 2.0 and P = 1025.2 kg/m3.Find the maximum total horizontal force and the maximum total moment on the pile.

Solution

Calculate

2gTd = 2)10()8.9(

8 = 8.16 x 10-3

From Figure 3.26 the breaking limit curve

2b

gTH = 0.006

Hb = 0.006 x 9.8 x 102 = 5.88 m

and

bHH =

88.55 = 0.85

From Figures 6.5 and 6.6 using 2gTd = 8.16 x 10-3 and

H = 0.85 Hb, Interpolating between curves H = Hb and H = 3/4 Hb; find

KDm = 0.620

Kim = 0.39

Fim = Cmρ4π D2HKim

Fim = 310)8.9)(2.1025)(2(

4π (1)2 x 5.0 x 0.39 = 30.77 kN

FDm = CD21 ρg DH2 x KDm

Berthing Structures


= 0.7 x 1/2 x (1025.2) (9.8) (1) (5)2 x 0.62

= 54504.76 N,

= 54.5 kN

W =HCDC

D

M

=)5()7.0()1()0.2( = 0.57

2gTH = 2)10()8.9(

5 = 0.005

2gTd = 0.0082

using the Figures 6.11 and 6.12 find φm

W = 0.5 φm = 0.34 (from Figure 6.11)

W = 1.0 φm = 0.44 (from Figure 6.12)

W = 0.57

Interpolating the values of 0.5 and 1.0 we can get the values for W = 0.57.

W = 0.57 φm = 0.354

Fm = φm ρg CDH2D

= 0.3554 (10,047) (0.7) (5)2 (1)

= 62241.2 N

Fm = 62.24 kN

From the Figure 6.8 Sim = 0.8

From the Figure 6.7 SDM = 0.996


466

Mim = Fim d Sim

= (30774) x 8 x 0.8 = 196953.6 N m = 196.9 kN m

MDM = FDM d SDM

= (545040.76) x (8) x (0.996)

= 434287.8 N m

4343 kN m

To find αm, using the Figure 6.15 and 6.16 are used.

W = 0.5 αm = 0.34 (from Figure 6.15)

W = 1.0 αm = 0.40 (from Figure 6.16)

Interpolating the values of 0.5 and 0.1, We can get the values of 0.57

W = 0.57 αm = 0.3484

Mm = αm ρg CDH2 Dd

= 0.3484 (10,047) (0.7) (5)2 (1) (8) = 490052.47 N m

Mm = 490 kN m.

6.3.8 Combination of Loads

The combination of loadings for design is dead load, vertical live loads, plus eitherberthing load, or line pull or earthquake or wave pressure, for open type berthing structure.The worst combination should be taken for design. In addition to the above load earthpressure & differential water pressure shall be consider for vertical force typing structures.

Berthing Structures


The partial safety factors for different types of loads in limit state design is given inTable 6.3 and increase in permissible stress for different combination of loads are given inTable 6.4.

6.3.9 Expert System

The Knowledge Based Expert System for estimation of forces in berthing structuresKNOWBEST have been developed at IIT Madras. (Sundaravadivelu & Ranga Rao(1996)). The user friendly menu driven expert system KNOWBEST not only helps the userto estimate various forces depending on the type of berthing structure (open type or closedtype) but also recommends the appropriate values of coefficients to be used for estimatingvarious forces.

Table 6.3 Partial Safety Factors for Loads in Limit State Design

LoadingPartial Safety Factor

Limit StateServiceability Limit State of Collapse

Dead load 1.0 1.0 1.5 1.2 (or 0.9) 1.2 (or 0.9) 1.2 (or 0.9)Vertical LiveLoad

1.0 1.0 1.5 1.2 (or 0.9) 1.2 (or 0.9) 1.2 (or 0.9)

Earth Pressure 1.0 1.0 1.0 1.0 1.0 1.0Hydrostatic andHydrodynamicForces

1.0 1.0 1.0 1.2 1.0 1.0

Berthing andMooring Forces - 1.0 1.5 - - -

SecondaryStresses 1.0 - - - - -

Wind Forces - - - - 1.5 -Seismic Forces - - - - - 1.5


468

Table 6.4 Increase in Permissible Stresses

Sl.No. Combination of Loads

Increase in PermissibleStress Increase in

AllowableBearingPressureReinforced

Concrete

OtherMaterials

such as steeland Timber

1 DL + LL + impact of breaking ortraction or vehicles + centrifugalforces of vehicles

Nil Nil Nil

2 DL + LL with impact, breaking ortractive and centrifugal forces + earthpressure, percent

15 15 15

3 DL with/without LL includingimpact, breaking or tractive andcentrifugal forces + earth pressure +hydrodynamic and hydrostatic forces+ berthing and mooring forces,percent

25 33 1/3 25

4 Wind forces on structures + loadcombination of (1) + (2) or (3)

5 Seismic forces + load combination of(1), (2) or (3)percent

6 Secondary stress + load combinationof (1), percent 15 15 15

7 Erection stage stresses with DL andappropriate LL + earth pressure +hydrodynamic forces + wind forces,percent

15 33 1/3 25

6.4 ANALYSIS OF BERTHING STRUCTURES

6.4.1 Analysis of a Bulk Berth

The layout of a berth to receive 30,000 DWT bulk carrier is given in Figure 6.19.The dimension of 30,000 DWT bulk carrier as per IS 4651 (Part III)-1974 are as follows:

Overall length = 205 mWidth = 26.5 mHeight = 14.3 m

Berthing Structures


Fully loaded draft = 10.7 m

The total length of the berth should be 10% more than the length of the ship. Hence alength of 250 m is adopted. The total length of the berth of 250 m is divided into fiveblocks each of 50 m length with expansion joints in between them. IS 4651 (Part IV)section 10 recommends a length of 39 m between the expansion joints. A spacing of 60 mis recommended for better stiffness. However 250m long berth without any

Fig. 6.19 Layout of Berth With 30000 Dwt Tanker

expansion joints are also constructed. However for these structures the loads due tovariation of temperature shall be considered in addition to other loads. The typical crosssection of a berth is shown in Figure 6.20. It consists of a diaphragm wall tied back by across beam to four rows of vertical pile.

The fully loaded draft is 10.7 m. Hence the dredge level is assumed as 10.7 + 10% of draft+ 0.5 m for over dredge allowance. Hence dredge level should be greater than 12.27 m.The dredge level is assumed as 12.5 m. The tidal levels are

HHWL = + 3.25 m

LLWL = + 0.40 m

25000

50000

20500

50000

M1 = STERN LINEM2 = AFT BREAST LINE

M4 = FORD SPRING LINEM5 = FORD BREAST LINEM6 = BOW LINEF1 & F2 = FENDERSB1 & B2 = BOLLARDS

M3 = AFT SPRING LINE

50000

M1

B1

M2

B2B33

M4

F1

5000050000

30000 DWT

B4F2

M3

B5

M5

B6

16


470

Fig.6.20Typical Cross Section of Fertilizer Berth

Hence the top level of the jetty is assumed as (3.25 + H/2 + 1) m where, H is the expectedwave height. The wave height inside the harbour during extreme weather condition is1.2 m. Hence the top level is assumed as + 4.85 m. The third and fourth row of piles areprovided below the conveyor columns, the second row of pile is provided below one of therails of crane track.

It is preferable to carry out three dimensional analysis for each block considering all therows of piles especially for berthing and mooring force. However it is a common practiceto carry out a two dimensional analysis for a typical pile bent for 1/3 of berthing force and1/3 or mooring force assuming that the berthing force and mooring force will bedistributed to 3 pile bents.

6.4.1.1 Preliminary Analysis of System

A typical 4 m panel of 1100 mm thick diaphragm wall having 3.65 m deep beam supportedby piles at 6 m, 12 m, 15.65 m and 22.45 m (Figure 6.21) is considered for the analysis.This depth of the beam is found to be very conservative. The economical depth is about

2515

-23.00

DREDGE LEVEL-12.50

+3.25HWL

+5.00

1100 THKDIAPHRAGM WALL

(B) FINAL DESIGN

-22.50

1000Ø PILE

1300ØPILE

-20.00

1300ØPILE

MAIN BEAM

Berthing Structures


Fig. 6.21 Idealization for Preliminary Analysis

-7.0m

500

3650

SECTION -YYSECTION - XX

7067-17.0m

5940115759800

71006942

6942

-23.0m

-21.0m

-19.0m

K(T/M)

8319

77871197920

-15.0m

-13.0m

-11.0m

-9.0m

4000

1100

V1

6800

+1.00 G.L BELOW DECK

XX

-5.0m

-3.0m

-1.0m

+1.0m

+3.0m

Y3

1

R3

V3V2

6000

Y

3950

TIE

R4

V4


472

1.65m. The preliminary analysis of the following three different systems (Raju et al.(1995)) has been carried out using the general purpose, Structural Analysis Program SAPIV developed by Bathe, K.J. (1973).

(A) Diaphragm wall with anchor rod and deadman diaphragm wall (Figure 6.22a).

(B) Diaphragm wall with vertical and raker piles (Figure 6.22b1 & 6.22b2).

(C) Diaphragm wall with vertical piles (Figure 6.22c1, 6.22c2 & 6.22c3).

For the purpose of analysis the deck, diaphragm wall and pile systems are replaced by two-dimensional beams. The passive pressure on the diaphragm wall is idealised by springelements. The piles are assumed to be rigid at top and bottom. The fixity depth for pilesas per IS 2911 (Part 1/ Se. 2) -1979 for an nh of 0.5 kg/cm3 is 5 times d, where d is the diaof the piles. Since the first row of piles is partly in the active zone of diaphragm wall, itsfixity depth is increased to 6 m + 5 d and fixity depth for 2nd, 3rd and 4th rows of piles areassumed as 5d.

Since the lateral load governs the design of these structures, the analysis is carried out forlateral loads only. The active earth pressure on the diaphragm wall and 100 T pull areconsidered as two typical load cases for the analysis.

The shear force in diaphragm wall and piles at the top, the wind force in the raker piles,anchor force in the tie rod and the horizontal deflections at the top of diagram wall aresummarized in Table 6.5.

Berthing Structures


Fig.6.22 Alternate Schemes

(b2) VERTICAL PILES WITH RAKER

100110 100 7575 110130 75

(c3) VERTICAL PILES

75100 130

(b1) VERTICAL PILES WITH RAKER

110 100 75100 110130

(a) VERTICAL PILES WITH ANCHOR

110 100 75 110130 100

75

(c2) VERTICAL PILES

100130100

75

(C1) VERTICAL PILES

100130100


474

Table 6.5

Berthing Structures


6.4.1.2 Results and Discussions

System ‘a’ - Diaphragm wall with tie rod and deadman diaphragm wall (Ref. Figure 6.25 and Table 6.5).

The active earth pressure in the diaphragm wall exerts a shear of 109 T at the top ofdiaphragm out of which only 38 T goes to the anchor rod; i.e., only 35% of the total shear.For a pull of 100 T, the anchor force is only 28 T i.e., 28%. The anchor is loaded onlyafter substantial lateral loads are transferred to the piles through the deep beam. Theconstruction of anchor with a deadman diaphragm wall of 750 mm thick is timeconsuming, expensive and is structurally inefficient in the present case in view of the4 large vertical piles. Hence it is desirable to eliminate the anchor and suitably strengthenthe 3rd and 4th row of piles to take care of the lateral load. The 3rd and 4th row of piles canbe strengthened either by increasing the diameter or by introducing additional raker piles.Results of both the alternatives are discussed below.

System ‘b’ - Diaphragm wall with Raker & Vertical Piles

Two different combination of raker and vertical piles are analysed. In b1 the 750mm diaraker pile is in the 3rd row and in b2, the raker pile is in the fourth row. It can beconcluded from the results that one 750 mm dia raker pile takes almost the same amount oflateral force as that of 3 numbers of 80 mm dia HTS anchor rods. Compared to system b2,system b1 performs better by taking more lateral load as axial force. The horizontaldisplacement at top of diaphragm wall for system b1 is also less than that of system b2 (Ref.Table 5).

Compared to the cost of installing 3 tie rods, the cost of installation of one 750mm diaraker piles is found to be cheaper.

System ‘c’ - Diaphragm wall with vertical piles

Three different combination of vertical piles are analysed. System c1 is similar to that ofsystem ‘a’ without anchor rod. In system ‘a’ pile 2,3 and 4 takes 32, 21 and 12%respectively of the total load while anchor takes about 28%. In system c1, the piles 2,3 and4 take 44, 28 and 17% respectively of the total load. In other words, the 28% load takenby the anchor rod is distributed to the 2nd, 3rd and 4th row piles as 12, 7 and 5% and theremaining 4% is transmitted to the diaphragm wall and pile 1.


476

The system c1 is found to be inadequate since the lateral load on pile 2 is more than 85 Tfor the combination of different loads. Hence, the 3rd and 4th row of pile diameter isincreased to 1300 & 1000 mm for system c2 and all the 3rd and 4th row of piles areincreased to 1300 mm diameter for system c3. The system c3 is finally chosen since itdistributes lateral load equally to the 2nd, 3rd and 4th row of piles. The typical cross sectionof the final system as adopted is shown in Figure 6.23.

6.4.1.3 Detailed Analysis

A rigorous analysis of the final system (Figure 6.23) has been carried out using SAP IVprogram, by idealising the soil support using springs for both the diaphragm wall and piles.The nodes are at 1 m intervals along the depth of the diaphragm wall and piles. Thesprings are also placed at 1 m intervals. The spring spacing shall be nearly equal to thethickness of diaphragm wall or the pile diameter for effective modeling of soil support infinite element analysis. The spring constants at each node is calculated as the reactionoffered by the soil in region 0.5 m above the node and 0.5 m below the node. The soilprofile is given in Figure 6.24. The active earth pressure is also calculated at 1 m intervalsand is applied as nodal load on the diaphragm wall. The nodal loads are given inFigure 6.25. The bending moment diagram for active earth pressure and a bollard pull of30 T are given in Figure 6.26 & 6.27 respectively.

Berthing Structures


Ø Ø Ø

Fig 6.23 Idealization for Rigorous Analysis

1100 mm THICKDIAPHRAGM WALL

-23.0m

-13.0m

395600600

1000 mmPILE-I

1300 mmPILE-II

1300 mmPILE-III

680

1300 mmPILE -IV

-8.0m

ACTIVEEARTHPRESSURE

+1.2m+1.2m

-3.2m


478

Fig. 6.24 Soil Profile

LEVEL IN M DESCRIPTIONY

(T/M ) (T/M )

CØ

(M)

H

(SPT)

N3 2

-0.78 YELLOW SAND 1.95 0.0 30° 1.63 10

-3.78 YELLOW SAND 1.95 0.0 33° 3.00 20

-4.98 BLACK CLAY 1.70 2.0 0° 1.20 03

-7.78 CRAY SAND 1.95 0.0 33° 2.80 20

-11.76 GREY SAND 1.95 0.0 31° 4.00 15

-13.78 BLACK CLAY 1.80 4.0 0° 2.00 10

-15.78 GREY SAND 1.95 0.0 36° 2.00 30

-19.78 YELLOW SAND 1.95 0.0 34° 4.00 25

-20.78 BROWNISH 1.95 0.0 38° 1.00 40

-24.00 1.95 0.0 45° 3.20 60

BROWNISH

SAND

SAND

BROWNISH

Berthing Structures


0.0

11.1

5.1

4.8

4.60

4.00

3.60

3.3

4.5

4.08

2.5

2.2

1.9

1.9

0.8

0 2 4 6 8 10

-13.0

-11.0

-9.0

-7.0

-5.0

-3.0

-1.0

+1.0

+3.0

LEV

EL IN

MEARTH PRESSURE (T/M2)

NODAL LOADS

(TONS)

NOTE: NODAL LOADS ARE FOR 1 metre WIDE PANEL

Fig. 6.25 Active Earth Pressure and Nodal Loads


480

Fig.6.26. B.M Due to Active Earth Pressure

Fig.6.27 B.M Due to Bollard Pull of 30 Tons

PILE IIPILE IDIAPHRAGM WALL PILE IVPILE III

-23.0m

-21.0m

-15.0m

-13.0m

-9.0m

22 12

1

BAC

DIAPHRAGM WALL PILE I PILE II

-5.0m

-1.0m

+3.0m1 3 E

D

-15.0m

-13.0m

-21.0m

-23.0m

PILE IVPILE III

187200

42

42

BA 2

+3.0m

-1.0m

-9.0m

-5.0m

1616

E

Berthing Structures


The soil reaction offered to the pile to resist lateral loads is nonlinear and hence, nonlinearsoil structure interaction of berthing structures is necessary. Either an iterative procedureor an incremental procedure can be used to implement the nonlinear behaviour (Ranga Rao& Sundaravadivelu (1995)) of soil structure interaction in the finite element analysis ofberthing structure.

6.4.2 Analysis of Jetty

A berthing structure with deck slab mounted on piles embedded into sea bed and which hasfree passage of water underneath the deck, is known as open type of jetty. The jettyprojects outward nearly perpendicular to or at some skew angle with the shore line. Thejetty (Figure 6.28) generally consists of two berthing dolphins, four mooring dolphins, jettyhead and an approach jetty.

Fig 6.28 Layout of Jetty

20m

ETHYLENE TANKER

75m

10m

25m 75m

8m8m

8m

15m

1.2m WIDE WALKWAY

8m JETTYHEAD

25m

1.2 m WIDE WALKWAY

10m 8m

8m

20m

STERNLINE

8m

8m

LIQUID ETHYLENEPIPELINE TO STORAGETANK

PILE APPROACH CUM PIPEBRIDGE

MOORINGDOLPHIN

MOORINGDOLPHIN

SHORELINE

BOWLINE


482

The increase in vessel size has necessitated construction of offshore jetty in deep water inopen sea and exposed to winds, waves and currents. Hence offshore jetty is a kind ofstructure totally different from those in a harbour. The length of approach jetty varies from1000 to 2500 m and an economical design of approach jetty can be made only afteranalysing different types of pile configuration for varying water depths. The approachjetty for a length of about 2500 m may have five to seven typical pile bents and each pilebent have to be analysed for different environment forces and soil strata. Anchor bentswith rakar piles to take of the longitudinal seismic / pipe line surge forces shall also have tobe provided and a three dimensional analysis is necessary for such situations. In additionthe berthing and mooring dolphins have to be designed not only for operating wavecondition but also for extreme wave condition, during cyclones. Hence a computer aidedanalysis and design is required for the offshore jetty.

The layout of a mooring dolphin is given in Figure 6.29. The mooring dolphin consists of16 piles of 760 mm dia. The four corner piles are kept vertical, whereas, the three piles ineach face is kept inclined, 3 vertical to 1 horizontal. This configuration has been chosenbased on the analysis of various configurations of piles (Ranga Rao & Sundaravadivelu(1994 A)). The mooring dolphin has 2440 mm thick deck slab. The dredge level is -14.00m and founding level is -24.6 m. The piles are assumed to be fixed at 5D below dredgelevel i.e., fixity level = 14 + (5 x 0.76) = -17.8 m.

The analysis is carried out using SAP IV idealising the piles by beam elements and thedeck using master slave option. The deck can also be idealised using brick element. In thiscase master-slave option is used since it is simple and gives comparable results with thebrick element idealisation of the deck.

The analysis is carried out for the following load cases:

(i) Dead load

(ii) Live load of 1 T/m2

(iii) 200 T bollard pull at θ equal to

(a) 45°

(b) 30°

(c) 15°

(d) 0°

Berthing Structures


Based on the results of the individual load cases (Table 6.6), the critical combination of thetensile and compressive forces on each pile is worked out.

Fig.6.29 Mooring Dolphin

910111213

14

15

16

1 4

6

7

8

2 3 5

3

1

3

1DREDGE LEVEL-16.00m

B SECTION 1-1

FOUNDING LEVEL-21.60m

2000

10000

2000

10000

10000A LAYOUT

10002000

1000

2000

2000

2000

+1.00m

+3.66m

2000 20001000

BOLLARD

1000


484

Table 6.6 Analysis of Mooring Dolphin

PileNo

Deadload

Live load(T/m2)

Axial forces in piles (T) due to200 T bollard pull at Max forces

45° 30° 15° 0° Tension Compression1 -50 -7 0

-96-58-31+99-31-58-96

0965831

-99315896

26 50 71 21 -572 -45 -6 -101 -99 -91 - -1523 -45 -6 -72 -80 -83 - -1344 -45 -6 -56 -76 -91 - -1425 -50 -7 97 87 71 49 -576 -45 -6 -6 20 46 - -977 -45 -6 -42 -22 0 - -1098 -45 -6 -85 -68 -46 - -1479 -50 -7 -26 -50 -71 - -128

10 -45 -6 102 99 91 57 -5111 -45 -6 72 80 83 38 -5112 -45 -6 56 76 92 47 -5113 -50 -7 -87 -87 -71 - -15614 -45 -6 6 -20 -46 - -9715 -45 -6 42 22 0 13 -5116 -45 -6 85 68 46 41 -51

6.4.3 Analysis of Container Berth

The typical layout of the extension of a container berth is given in Figure 6.30.The proposed extension of 220m of the container berth is divided into 4 blocks, each of55 m. The width of the container berth is 20 m. The span of the container crane is 30 m.It will be uneconomical to provide 30 m width for the container berth and hence one rowof piles are provided behind the berth to support the near rail of the container crane. Twocontainer cranes are considered for the analysis. Each container has four legs and eachlegs has 8 wheels. The center to center distance between two legs is 16.5 m and center tocenter distance between two wheel is 0.8 m. The deck system consists of 0.4 m thick RCCslab, 0.05 m thick wearing coat, eight main beams of size 0.8 x 2.45 m, twelve secondarybeams, three facia beams of size 1.0 x 2.45 m (Figure 6.31). The depth of the webs of allthe beams are inclusive of the slab thickness except for the secondary beam which is notintegral with the slab.

Berthing Structures


Fig.

6.3

0 .

Lay

out o

f Con

tain

er B

erth

LAN

D S

IDE

MO

OR

ING

1300

Ø P

ILE

CR

AN

E R

AIL

PILE

MU

FF

FEN

DER

29

30

31

32

211791

22

23

1810

1911

242012

3

CL

OF

CR

AN

E 1

4

KEY

PLA

N

ALL DIMENSIONS ARE IN mm.

33

34

35A

36

30000

2113

26

27

2214

2315

5

CL

OF

CR

AN

E 2

6

7

282016860

00

5500

0

1850

0 6380

8380

6400

1900

0

4000

9000

5550

4500

1000

1038

0

1650

0

4900

4500

4000

1650

1000

8380

900

0

5500

0

5550

4900

1850

0

638

010

380

1038

0

5500

055

000

2000

0

1650

0 8380

8380

8380

5500

0

1650


486

Three berthing points are provided for each panel, one at the middle and others at 10.74 mfrom each end of the panel. The mooring points are provided at 18.5 m c/c with theextreme one at 9 m from the respective panel edge. The various levels are given below.

Top level of deck : + 4.00 m

Lowest mean water level : 0.00 m

The actual dredge level : - 13.75 m

The design dredge level : - 14.00 m

Cut-off level of piles : +1.50 m

The following loads are considered for the analysis.

a) Dead load

b) Live load = 5.5T/m2 on deck slab

838

500

11 x 1480

152

200

200

MB2MB1

490165

CB

FB

SB12

SB11

SB10

SB9

SB8

SB7

SB6

SB5

SB4

SB3

SB2

SB1

Only CL of the beams are shown

FB - Fender beam - 1000x2450

CB - Crane beam - 700x1200

(Depth of the beam Exclusive

SB - Secondary Beam -400x1000

MB3

All Dimensions are in mm

of slab thickness)

MB - Main Beam -800x2450

Berthing Structures


c) Crane Loads : Crane operating = Each Wheel Load is 40 t with 20%

Impact and 10% tractive force

Crane Idle = Each Wheel Load is 33.33t

d) Berthing Force = 250 t at left or central or right berthing points

e) Mooring force (M.F) = 150 t at left, central or right mooring points

f) Seismic Force = 2% of (D.L + 50% L.L) (As per IS 1893 for Zone II)

6.4.3.1 Load Combinations

i) a + b + c+ dii) a + diii) a + eiv) b + c + 250 T berthing force across the berth and 82 T along the berth at

any one berthing pointv) a + fvi) a + cvii) a + bviii) a + b + c

The increase in the permissible stresses for load combinations (i) to (v) as per IS-4651(Part IV) is 25 % and the same is assumed in design.

6.4.3.2 Structural Analysis

The berth is analysed as a three dimensional structure using SAP IV Program (StructuralAnalysis Program - IV an inbuilt computer program). The pile is assumed to be fixed at 5‘D’ below the dredge level. Based on the results of the analysis, the piles are divided intofour major groups and the axial forces and bending moments for two critical combinationsare given in Table 6.7. Since 25% overstress is allowed for these combinations, the forcesare reduced by 25% and the piles are designed.

6.4.3.3 Structural Design of Piles

Piles in Group I (23-26) are provided with 2.25% steel, Piles in Group 2 (11-14, 31-34) areprovided with 0.8 % steel, Piles in Group 3 (2-7, 10, 15, 18, 19, 22, 29, 30, 35, 36) areprovided with 3.0% steel and Piles in Group 4 (1,8, 9, 16, 17, 20, 21, 28) are provided with2 % steel. Figure 6.32 and Table 6.8 gives the reinforcement details. Structural design ofpiles is done using the design charts for the circular piles given by Manohar, S.N. (1964).


488

Fig

6.32

Pi

le r

einf

orce

men

t det

ails

Berthing Structures


Table 6.7 Design Forces in Piles

PileGroup No Pile Numbers

Critical Load Combinations1 2

AxialLoad (T)

BendingMoment (T-m)

Axial Load(T)

Bending Moment(T-m)

I 23, 24, 25,26 533 144 160 150

II 11, 12, 13, 1431, 32, 33, 34

478 105 143 90

III 2 to 7, 10, 14,10, 15, 18, 1922, 27, 29 30,35, 36

375 158 59 156

IV 1, 8, 9, 16, 1720, 21, 28

197 155 112 143

Table 6.8 Reinforcement Details

Pile GroupNo.

Percentageof Steel (p)

Area of Steel(m2)

No. Of 32 mm φ bars in Lateral ties

Zone ‘m’ Zone ‘n’

I 2.25 0.0299 38 26Provide Y10-300throughout thelength of pile

II 0.80 0.0107 14 14 -Do-

III 3.00 0.0399 51 34 -Do-

IV 2.00 0.0266 34 24 -Do-


490

6.4.3.4 Foundation Design of Piles

The piles are designed based on the soil profile. The soil profile indicates silty sand from –14.0 m to – 22.0 m ( SPT ‘N’ =30), cemented sand from -22.0m to -25.0m (SPT ‘N’ = 50)and rock (SPT ‘N’ >100) for depth below –25.0m. However rock level varies at certainlocations. Though 1300mm dia piles founded at -23 m level are found adequate as a goodengineering practice, founding depth is adopted with penetration ½ times diameter of pilein hard rock or 3 times diameter of pile in cemented sand strata whichever is earlier. Thepile capacities are worked out based on SPT ‘N’ values and using Meyerhof’s correlationsas given below.

Ultimate end bearing resistance in sand = 12 [ SPT ‘N’] T/m2

Ultimate skin friction in sand = [ SPT ‘N’] /10 T/m2

The capacity in rock is worked out as per Cole & Stroud as given below.

qa = Nc Cb/F

fa = αCs

where

qa = allowable end bearing pressure

Nc = bearing capacity factor taken as 9.0

Cb = shear strength of the rock at pile base

F = factor of safety taken as 3.0

fa = allowable frictional resistance

Cs = average shear strength of rock along rock socket and

α = shaft adhesion factor taken as 0.3.

For silty sand [ SPT ‘N’ = 30]

Ultimate end bearing = 12 x 30 = 360 T/m2

Allowable end bearing = 144 T/m2 (ultimate end bearing /2.5)

Ultimate skin friction = 30/10 = 3 T/m2

Allowable skin friction = 3/2.5 = 1.2 T/m2

Berthing Structures


For cemented sand [ SPT ‘N’ = 50]

Ultimate end bearing = 12 x 50 = 600 T/m2

Allowable end bearing = 600/2.5 = 240 T/m2

Ultimate skin friction = 50/10 = 5 T/m2

Allowable skin friction = 5/2.5 = 2 T/m2

For Rock

For N > 100, taking the shear strength of rock from chart given by Cole & Stroud as90 T/m2

Allowable friction resistance = 0.3 x 90 = 27 T/m2

Allowable end bearing = 9 x 90/3 = 270 T/m2

Pile Group I

Total load = 427 T

End bearing in rock = 27043.1 2

××π = 358.37 = 358 T

Total skin friction from silty sand and cemented sand layers

1.3 (1.2 x 8 + 2 x 3) = 63.71 = 64 T

Required skin friction capacity from rock

427 - (358 + 64) = 5 T

A penetration of 1 m into the rock is recommended.

Hence, the founding depth of piles in Group I shall be -27.0 or 1 m penetration into hardrock which ever is earlier.

Pile Group II

Total load = 383 T

End bearing from cemented sand layer = T55.3182403.14

2 =××π

Skin friction from cemented sand layer & silty sand layer = 63.71 T


492

Total load = 318.55 + 63.71 = 382.26 T = 383 T

Give a penetration of 1 m into the rock. Hence, the founding level of piles in Group IIshall be - 26.0 m or 1 m penetration into rock, whichever is earlier.

Pile Group III

Total load = 300 T

Hence, the total load required is less than the end bearing capacity of cemented sand layer.But from the minimum embedment depth criterion, an embedment depth of 5 times thediameter of the pile should be provided. 5 x 1.3 = 6.5 m. But, this falls in the silty sandlayer.

Hence, give a penetration of 1 m in the cemented sand layer.

Hence the founding depth for the piles in Group III shall be - 23.0. Similarly the foundingdepth of piles in Group IV shall also be -23.0 m.

As the spacing between the groups of piles (23,24,25,26) & (31,32,33,34) is only 4.9 m,the foundling level for both these groups is kept as 1 m penetration to the rock or -27.0 mwhichever is earlier.

For the same reason as stated above for the two groups of piles (11,12,13,14) & (3,4,5,6)the founding level is kept as 1 m penetration into the rock or -26 m, whichever is earlier.

For the rest of the piles the founding level is -23.0 m.

6.5 DESIGN OF BERTHING STRUCTURES

Once the analysis of any structural system is completed, the next step would be the designof various elements in the structural system. Generally, the design process is iterative asthe design variables chosen may not satisfy the allowable stress/strain parameters. Thisprocess should be repeated until a satisfactory solution is obtained. The design shall becarried out as per the guidelines specified in IS 456-1978. As per IS 4651 (Part IV) - 1989the minimum grade of concrete to be used in berthing structures is specified as M 30. Theminimum cement content of 0.4 T/m3 and maximum water cement ratio of 0.45 shall bemaintained for all grades of concrete. The minimum thickness of cover for structures

Berthing Structures


immersed in sea water, in splash zone or exposed to marine atmosphere should be 25 mmmore than the cover specified in 4.1 IS 456 (1978)

Hence the cover shall be as follows

Slab = 15+25 = 40 mm

Beam =25+25 = 50 mm

Pile = 40 + 25 + = 65 mm

However the cover shall not be greater than 75 mm.

There are two methods of design namely, Working Stress method and the Limit Statemethod. In the working stress method the design is based on the linear stress strainrelationship within the elastic limit. The structure shall be designed for the working loadsand checked for the permissible stresses. The permissible stresses are the stresses obtainedafter applying a factor of safety to the yield strength of the materials.

In the limit state method the design is based on Limit State concept. The structure shall bedesigned to withstand safely all the loads liable to act on it throughout its life. It shall alsosatisfy the serviceability requirements such as limitations on deflection and cracking. Theacceptable limit for the safety and serviceability requirements before failure occurs iscalled a “Limit State”. The diaphragm wall and pile are the two important structuralelements of a berthing structure and the detailed design method for the diaphragm wall andpile is given in this section.

6.5.1 Design of Diaphragm Wall

The diaphragm wall is to be designed using the design philosophy given in the followingsection. Requirements of reinforcement are given in Section 6.5.1.2.

6.5.1.1 Design Philosophy

The basic assumption is that the maximum strain in concrete at the outermost compressionis 0.0035, when the neutral axis lies within the section. The strain varies from 0.0035 athighly compressed edge to zero at the opposite edge when the neutral axis lies along oneedge of the section. For purely axial compression, the strain is assumed to be uniformlyequal to 0.002 across the section. The strain distribution lines for these two cases intersecteach other at a depth of (3/7) D from the highly compressed edge. This point is assumed to


494

act as a fulcrum for the strain distribution line when the neutral axis lies outside the sectionas shown in Figure 6.33.

Fig 6.33 Strain Diagrams

Neutral Axis Lying Outside Section:

When the neutral axis lies outside the section, the shape of the stress block will be asindicated in Figure 6.34. The stress is uniform for a distance of (3/7)D from highlycompressed edge because the strain is more than 0.002 and thereafter the stress diagram isparabolic. Let xu = kD and let ‘g’ be the difference between the stress at the highlycompressed edge and the stress at the least compressed edge. Considering the geometricalproperties of a parabola,

0.0035

NEUTRAL AXISWITHIN THE SECTION

0.0035

0.002

a

X

x

b

d'

CENTRODAL AXIS

d'yi

HIGHLY COMPRESSEDEDGE

Berthing Structures


Fig. 6.34 Stress Block when the Neutral Axis lies Outside Section

2

ck 3k74

f446.0g

−

= (6.21)

Area of the stress block

=

−−

2

ck 3k74

2141Df446.0 (6.22)

The centroid of the stress block will be found by taking moments about the highlycompressed edge.

STRAIN DIAGRAM

b

D

STRESS DIAGRAM


496

Moment about the highly compressed edge

= 22

ck gD498

2Df446.0 − (6.23)

The position of the centroid is obtained by dividing the moment by area.

While designing the diaphragm wall, the neutral axis at regular intervals is assumed. Foreach position of neutral axis, the strain distribution across the section and the stress blockparameters are determined as explained earlier. The stresses in the reinforcement are alsocalculated from the strains. Thereafter the resultant axial force and the moment about thecentroid of the section are calculated as follows:

)ff(100pibDDbfCP cisi

n

1ick1u −+= ∑

=

(6.24)

where

C1 = Coefficient for the area of stress block

Pi = (Asi/bD) where Asi is the area of reinforcement in the ith rowfsi = Stress in the ith row of reinforcement, compression being positive and

tension being negative

fci = Stress in concrete at the level of ith row of reinforcement

n = Number of rows of reinforcement

Taking moment of forces about the centroid of the section,

yi)ff(100pibDDC

2DDbfCM cisi

n

1i2ck1u −+

−= ∑=

(6.25)

where

C2D = the distance of the centroid of the concrete stress block, measured from the highly compressed edge

yi = the distance from the centroid of the section to the ith row of the reinforcement, positive towards the highly compressed edge and negative towards the least compressed edge.

Berthing Structures


Neutral Axis Lies Within Section:

In this case, the stress block parameters are simpler and they can be directly incorporatedinto the expressions which are otherwise same as for the earlier case. Thus the followingexpressions are obtained

)ff(100pibDDkbf36.0P cisi

n

1ick −+= ∑

=

(6.26)

yi)ff(100pibD)k416.05.0(kDbf36.0M cisi

n

1i

2ck −+−= ∑

=

(6.27)

6.5.1.2 Requirements of Reinforcement

The minimum reinforcement of 0.4% and the maximum reinforcement of 4% areincorporated for the design of diaphragm wall.

The shear reinforcement shall be provided to carry a shear equal to Vs = V-τc.bd. Thespacing of the vertical stirrups, sv is given by

S

svyv V

dAf87.0S = (6.28)

where

V = Shear force due to design loads

Vs = Strength of shear reinforcement

Asv = Total cross sectional area of stirrup legs

sv = Spacing of the stirrups along the length of the member

τc = Design shear strength of the concrete

fy = Characteristic strength of the stirrup, which shall not be greater than 415 N/mm2

6.5.2 Design of Pile

Circular piles are widely used as foundations for coastal and offshore structures like berths,jetties, dolphins etc. Circular piles are preferred in these structures because they can beeasily installed with a liner. As these sections have uniform c/s about any diametrical axis,


498

these sections are best suited to resist multi-directional wave loads (Srinivas &Sundaravadivelu (1987)). Piles are designed by working stress method to limit crackwidth.

6.5.2.1 Design Philosophy

The design of compression members can be carried out in two distinct stages.

1. Design based on uncracked section, i.e. there is no tension anywhere in the sectionor the resultant tensile stress is less than the permissible tensile stress of concrete.

2. Design based on cracked section, i.e. the resultant tensile stress is more than thepermissible tensile stress in concrete.

Design of Uncracked Sections:

In general, for an assumed percentage of reinforcement and neutral axis depth the stressesunder given loading are checked against permissible stresses. The various steps involvedin the design are as follows:

1. Check by interaction formula : The interaction formula as given below has to besatisfied.

1ff

cbc

cbc

cc

cc ≤σ

+σ

(6.29)

fcc = Calculated direct compressive stress in concrete

σcc = Permissible axial compressible stress in concrete

fcbc = Calculated bending compressive stress in concrete

σcbc = Permissible bending compressive stress in concrete

For more exact calculations, the maximum permissible stress in a reinforced column orpart there of having a ratio of effective column length to least radius of gyration above 40shall not exceed those which result from multiplication of the appropriate maximumpermissible stresses by the reduction coefficient, Cr given by the following formula

Cr = 1.25 - (lef)/(160 )imin (6.30)

imin = Least radius of gyration

Berthing Structures


lef = Effective length of column (pile)

If the assumed section satisfies interaction formula, then it has to be checked for cracking.

2. Check for cracking : If fcc is greater than fcbc, there is no tension in the concrete andhence the section is considered as uncracked. Even if fcc is less than fcbc, the section isconsidered to be uncracked if the resultant stress given by ft = fcbc -fcc is less than (i) 0.75times the modulus of rupture of given grade of concrete at seven days; (ii) 0.25 times themaximum resultant compressive stress given by (fcc + fcbc). If ft is greater than either (i) or(ii), then the section is considered to be cracked.

Design of Cracked Section:

In case of cracked section design, the tensile stress of concrete is ignored. The design ofcracked section is carried out using two equilibrium equations.

P = Cc + Cs - T (Force equilibrium) (6.31)

M = Cc Xc + Cs Xsc + TXst (Moment equilibrium) (6.32)

Where

Cc = Compression in concrete segment.

=

ββ+

ββ−

ββ− 4

2sincos2

cos3

sin)cos1(

Rf2 32cbc (6.33)

Cs = Compression in steel reinforcement.

=)cos1(100

pRf 2cbc

β− (1.5 m - 1) (1-d/R) (sin α - α α) (6.34)

T = Tension in steel reinforcement.

=)cos1(100

mpRf 2cbc

β− (1-d/R) (sin α + (π - α) cos α) (6.35)

Cc Xc = Moment of compression in concrete about the center line.


500

=

β−

ββ−

ββ− 32

4sin3sincos

8)cos1(Rf2 33

cbc (6.36)

Cs Xsc = Moment of compression of steel about the center line.

=

α

−α

−−β− 4

2sin2

)R/'d1()1m5.1()cos1(100

pRf 23

cbc (6.37)

TXst = Moment of tension in steel about the center line.

=

α

+α−π

−β− 4

2sin2

)R/'d1()cos1(100

mpRf 23

cbc (6.38)

Equations (6.11) and (6.12) have to be solved for fcbc and either α or β. Usually trial anderror method is used to solve these equations. Once these two equations are solved thestress in steel can be determined by using the following equations.

n)'dnR2(mf

f cbcst

−−= (6.39)

where

n = depth of neutral axis

= R (1 - cos α) (6.40)

= (R - r cosβ) (6.41)

Knowing the stress in steel, cover to the reinforcement and modulus of elasticity ofconcrete, crack width can be calculated using appropriate crack width formula.

6.5.2.2 Requirements of Reinforcement

The reinforcement shall not be less than 0.4% as per IS 2911 (part I)-1979. In generalmaximum reinforcement of 4% is considered in the design due to the difficulty in placingmore than 4% reinforcement. The diameter of the reinforcement bar shall not be less than12 mm.

The diameter of the lateral ties shall be not less than one-fourth of the diameter of thelargest longitudinal bar, and in no case less than 5 mm. The spacing of the transversereinforcement shall not be more than the least of the following distances:

Berthing Structures


i) The least lateral dimension of the compression member

ii) Sixteen times the smallest diameter of the longitudinal reinforcement bar to be tied

iii) Forty-eight times the diameter of the transverse reinforcement

6.5.3 Calculation of Crack Width

Concrete is weak in tension and cracks when the tensile strain is of the order of0.0002 to 0.0005. With the advent of high tensile steel, the strain in the concretesurrounding such reinforcement will be of the order of 0.001 even under service loads. Infact, the reinforcement becomes effective only when the surrounding concrete cracks.However, large scale cracking is not acceptable because of its ugliness and the resultantingress of moisture and eventual corrosion.

A dense concrete with adequate cover to the reinforcement can protect it during the entireuseful life of the structural component. But cracking permits the ingress of carbon dioxide,chlorides, etc. thus initiating corrosion. Direct and indirect financial losses due tocorrosion runs to several millions of rupees in India and hence the limit state of clacking isincluded as one of the important design limit states. Concrete cracks even when there is noexternal load applied on a structure, mainly due to shrinkage and temperature effects.

Tension members of reinforced concrete have cracks penetrating right through the crosssection and steel reinforcement is the only connecting link between the various parts. Suchcracks are called as separation cracks. On the other hand, the reinforced concrete membersubjected to pure flexure has cracks in the tensile zone only and they penetrate the crosssection of the member up to the neutral axis. These flexural cracks are of primary concernto the designers.

For purposes of crack control, it is essential to define the admissible crack width. As perIS 4651 (Part IV)- 1989 the crack width should be less than 0.004 times the coverprovided. Many research organizations and codes like CEB/FIP, ACI Code, RussianCode, DIN Code, British Code, IRC Code etc., have recommended various formulae forthe calculation of crack width. Many of these formulae are arrived at conductingexperiments on rectangular beams subjected to bending moment only. Consequently theexpressions derived have included the width of the section as a parameter. Only IRCformula appears to be applicable for circular piles because it involves only stress in steeland effective cover concrete.


502

The formulae given by CEB/FIP, IRC and SP24 are given below.

6.5.3.1 CEB/FIP Formula

CEB/FIP recommends the following formula to calculate the crack width (Cw),

Cw = (1.5 C + 16φ/Pf) (σs - 3000/Pf) x 10-6 (6.42)

Where

C = Effective cover

φ = Diameter of the reinforcing bar

σs = Stress in tensile steel

Pf = (100 Ast)/(0.25 bh)

Ast = Area of tensile steel

b = Breadth of the section

h = Depth of the section

6.5.3.2 IRC Formula

The IRC formula is given for bridge like structures to calculate the crack width. Asberthing structures are also subjected to truck loads such as class AA etc., the formulagiven by IRC has been used to calculate the crack width. The formula given by IRC tocalculate crack width, Cw is as follows:

Cw = (3.3 fst dc)/(m Ec) (6.43)where

fst = Stress in steel

dc = Effective cover

m = Modular ratio

Ec = Modulus of elasticity of concrete

Berthing Structures


6.5.3.3 IS code (SP 24) Formula

As per SP 24, the crack width, Cw is calculated as follows:

Caa C

D x

wcr m

cr=

+−

−

3

12

ε( )min

(6.44)

where

acr = Distance from the point considered to the surface of the nearest longitudinal bar

Cmin = Minimum cover to the longitudinal bar

εm = Average strain at the level considered

D = Overall depth of the member

x = Depth of neutral axis

The average strain at the level at which cracking is being considering is given by

3

sst

t1m 10x

f)xd(A)x'a(Db7.0 −

−−

−ε=ε (6.45)

Where

ε1 = The strain at the level considered ignoring the concrete in the tension zone

bt = The width of the section at the centroid of the tension steel

a’ = The distance from the compression face to the point of the crack

Ast = The area of tension steel

fs = Service stress in tension reinforcement which may be taken as

=providedArequiredAf58.0

st

sty× (6.46)

The above formulae can be used provided the strain in tension reinforcement does notexceed 0.8 fy/Es. The negative value of εm indicates that the section is uncracked. Inassessing the strains, the modulus of elasticity of concrete shall be taken as 280/3 σcbc asgiven in elastic theory to account for creep.


504

6.5.4 Computer Aided Design

Since the design of berthing structures involves analysis of various configurationsconsidering nonlinear behaviour of soil, and, codal provisions for crack width calculations,computer aided design of berthing structures has become necessary (Ranga Rao &Sundaravadivelu (1994).

6.6 MARINE FENDERING SYSTEMS

6.6.1 General

The purpose of the marine fendering system is to prevent damage to both the vessel andberth, during the berthing process and while the vessel is moored. As the vessel approachesa berth it possess kinetic energy by virtue of its displacement and motion. As the vesselcontacts the berth and is brought to stop this kinetic energy must be dissipated. Fenderingsystems that is being berthed are provided to absorb or dissipate the kinetic energy of theship.

6.6.2 Types of Fendering Systems

The different types of fendering systems are as follows:

1. Standard pile fenders

2. Rubber fenders

3. Pneumatic fenders

4. Gravity type fenders

6.6.2.1 Standard Pile Fenders

This system is generally used for low energy absorption. The piles made of timber, steel.RCC and PSC are driven in front of the berthing structure to absorb the energy from theship by direct compression and flexure. The energy capacity depends on the size, shapeand length of the pile. Wooden piles does not have long life while the RCC piles have lowenergy absorption. Steel piles and PSC piles with rubber buffers are used for larger depths.

Berthing Structures


6.6.2.2 Rubber Fenders

The few types of rubber fenders are shear, compression and buckling. The shear andcompression fenders, have a linear P - ∆ relation, i.e. for energies smaller than the ratedenergy, the fender will be relatively soft. The buckling fenders, have swift increase inloads in the initial stages, but as the fenders are further deflected the loads are more or lessmaintained until the rated deflection is reached. A low ratio of load over energy (P/E) isreached for buckling fenders.

6.6.2.3 Pneumatic Fenders

Pneumatic fenders are originally developed for ship to ship transfer but now-a-days areused for jetties and berths also because of its good performance. The pneumatic fender isan inflated rubber bag and dimensions vary from 0.5m to 4.5 m in dia and 1m to 12 m inlength. The fender bag is protected by wire or chain net with tyres or rubber sleeves. Theenergy absorption does not decline at inclined compression for these fenders.

6.6.2.4 Gravity Type Fenders

These are generally made of concrete blocks suspended from a heavily constructed wharfwork. the Impact energy is absorbed by moving and lifting the heavy concrete block.

6.6.3 Selection Criteria of Fendering Systems

The selection of a optimum fender for a given service depends on the following factors :

1. The type, size, draft and allowable hull pressure of a vessel.

2. Berthing velocity and angle.

3. Distance between the berthing point and the vessels gravity centre measured along theface of the pier.

4. Water level, tidal range, wind velocity, direction of wind, direction and velocity ofcurrents.

5. Behaviour and installation pitches of Dock fender

6. Structure and strength of Berthing facilities

7. Certain human factors involved in berthing.


506

6.6.4 Berthing Energy of a Vessel

The design of fenders depends very much on the energy to be absorbed by the fendersduring berthing. When a ship strikes the fender, it transfers some part of the kinetic energyto the fender and the other part gets dissipated to the motion of ship in water. Some part ofthe energy absorbed by the fender is transferred back to the ship, after the ship has come torest, by the fender trying to recoil back to its normal shape. This process of exchange ofenergies between fender, ship and the loss of energy in water motion continues till thewhole of the kinetic energy of ship is dissipated in water motion. The different methodsthat are used in determining the maximum amount of energy to be absorbed by the fenderis given below :

6.6.4.1 Quinn Method

In this method fifty percent of the energy of the ship calculated on the basis of the velocityof the ship normal to berthing structure is assumed as the energy absorbed by the fender.

4V

GWE

2

= (6.47)

6.6.4.2 Woodruff Method

In this method the following empirical equation is used to calculate the berthing energy.

E = W(0.004 - W x 10-8 (6.48)

Where W is in tons and E is in ton feet.

6.6.4.3 Vasco Costa Method

Vasco Costa has given the following analytical solution, for a ship moving with translatoryvelocity u and angular velocity w, having no slip along the berth.

E = (WV2/2g) (1 + 2D/B) (K2 + r2 Cos2r / K2 + r2) (6.49)

Where v Distance P= u + aw

The value of k can be taken as 0.2 L to 0.29 L. The following three coefficients are to beconsidered along with equation.

Berthing Structures


1. Geometric coefficient (Cg) 0.85 for convex surface contact of theship 1.00 for broad side berthing1.25 for concave surface contact ofthe ship.

2. Deformation coefficient (Cd) 0.5 for resilient fender and 1.0 for stiff fender

3. Berth configuration Coefficient (Cc) 0.8 for closed warf and 0.9 for closedberth and 1.0 for open type berth

6.6.4.4 IS: 4651 (Part III) - 1974

As per the Indian standard code of practice, the berthing energy is calculated as follows

memD CxCxC

g2VxWE

2

= (6.50)

where

WD = Displacement tonnage (DT) of the vessel, in tonnes,

V = Velocity of vessel in m/s, normal to the berth

g = Acceleration due to gravity in m/s2

Cm = Mass coefficient

Ce = Eccentricity coefficient andCs = Softness coefficient.

The approach velocity varies from 0.1 m/s to 0.75 m/s depending on the size of the vessel,site condition and berthing condition. The above equation depends on the angle ofapproach and l/r ratio where l is the distance from the centre of gravity of the vessel to thepoint of contact projected along the water line of the berth in metre and r is the radius ofgyration of rotational radius on the plane of the vessel from its centre of gravity in metre.

The l/r ratio is in the range of 1 to 1.25. The angle of approach varies from0 to 20 degrees. The softness coefficient indicates the relation between the rigidity of thevessel and that of the fender. The value of 0.9 is generally used for this factor.


508

6.6.5 Fender Reaction

The fender reaction depends on the approximate energy to be absorbed and thecharacteristics of the fender. If the fender reactions are transmitted to the backfillimmediately behind the quay wall there will be no problem in absorbing the reaction. Ifthe structure, like open piers and jetties are to be designed for these reaction forces, theforces are critical since they control the design of these structures. If P/E ratio varies from2 to 7 depending on the type of fender where P is the berthing force in T and E is theenergy absorption at 50 % of defletion in T. m, in such cases it is preferable to havefenders with low reaction per absorbed unity of energy (P/E). It is also important toconsider the fender performance beyond the rated energy capacity, since the fenderreaction increases swiftly.

6.7 SINGLE BUOY MOORING SYSTEM

6.7.1 General

The art of implanting floating structures in the ocean is as old as man’s history. Markerbuoys, mooring buoys and navigational buoys have long been familiar sights in theharbours and waterways and along the sea shores. The recent past has seen many large andsophisticated buoy mooring systems deployed in deep waters for a variety of purposes.

A buoy mooring system consists of a buoy or buoys, connected by cables and anchored tothe seabed. Being a compliant structure, the system is responsive to external effects and themovements are controlled by the mooring system. Buoy mooring systems are flexible andprovide a progressive elastic response to environmental forces absorbing and dissipatingenergy from the ocean environment. To understand the effect of these constrained or freelydrifting buoyant structures often require advanced Engineering knowledge from manydisciplines are often required.

A buoy can be considered as a major positively buoyant component in the system. Buoysmay be classified, based on their position into three general groups, as (i) surface buoysystem where the buoy floats on the surface (ii) subsurface buoy system where the buoy isbelow the sea surface and (iii) two part buoy system where it is a combination of the abovetwo systems.

Surface buoys can be surface following type with shapes such as spherical, cylindrical,disks etc. or surface decoupled such as spars. Surface following buoys have the advantageof having a large buoyancy to drag ratio whereas the spar buoys have small buoyancy to

Berthing Structures


drag ratio and they are not effective in providing the buoyancy required to support longmooring lines.

Surface buoys are used at the air sea interface in the upper part of the water column. Theseare further classified as single leg surface buoy systems and multi-leg surface buoysystems. In the single leg surface buoy system, there is only one anchoring point.

The ratio of mooring cable length to water depth is called the scope of the mooring line. Asmall scope indicates a taut moor and a large scope indicates a slack moor. The advantagesof a taut moor are smaller buoy-watch-circle, reduced sensor motion and ease ofdeployment. The disadvantages of the taut mooring system are high dynamic loading dueto wave action and high static tension under severe current conditions. These are reducedwhen the scope of the mooring line is increased. The motion of the float and of the sensorsa slack moored system will become considerable, thus introducing an undesirable error inthe measurements of velocity fields and other ocean variables.

Subsurface buoy systems are also classified as single leg and multi-leg subsurface buoysystems. The great majority of oceanographic subsurface buoy systems have a singleanchoring point. Cost efficiency and ease of deployment result from their simpleconfiguration. As the buoy would be much below water surface, the wave force and themotion of the buoy due to waves would be less.

Two part buoy systems are used when the need arises to provide motion stability forunderwater sensors and at the same time to provide a surface expression for telemetry ofdata or for relocation of the main buoy system. The motion stability is provided by using asubsurface supported buoy system.

A typical deep water buoy system may involve multiple lines with lengths varying from afew tens of metres to thousands of metres. When these are considered in conjunction withthe equipment deployed from or associated with the moored buoys, the losses resultingfrom a mooring failure can be significant. Consequently there is much interest in designand analysis methods applicable to the buoy mooring systems.

In general, based on the use of the buoy mooring system it can be grouped as (i) buoysused for monitoring or measuring the parameters of importance to oceanographers andnaval scientists and (ii) buoys used for engineering purposes such as mooring oil tankers.


510

6.7.2 Oceanographic Buoy Systems

An oceanographic buoy system can be defined as a floating structure deployed in the oceanfor the purpose of measuring environmental data (Berteaux, 1976). Because of theirinherent capacity of efficiently providing long term series measurements of meteorologicaland oceanographic parameters, a relatively large number of buoy systems are deployedeach year in world’s oceans.

Buoy systems are used in the ocean environment for monitoring weather, oceanographicand defence related data acquisition, and also as vehicles for electronic navigationalsystems. An array of hydrophones used in conjunction with a subsurface moored buoy anda telemetry system can be used as a passive sonar to detect and transmit sounds in the seaeither due to surface or subsurface ships. Standard navigation systems can be installedaboard floats, provided with power and moored offshore to extend the range of precisionnavigation. In the Ocean Acoustic Tomographic System (OATS), the use of buoy cablesystem would help to get very valuable oceanographic and scientific data.

6.7.3 Offshore Floating Storage Systems

Since many large oil fields are in remote places where harbours are non-existent, a need isfelt to have artificial berths to moor the tankers during their loading operation. Manyconfigurations of offshore tanker terminals are attempted. The single point mooring system(SPM) has emerged as the most rapidly deployed, economical and safest to operate. SPMenables economic transport of crude oil where use of pipelines is not technically oreconomically feasible because of rough seabed, topography or long distances from shore.

Single point mooring terminals are, as the name implies, facilities of small horizontaldimensions, to which large vessels are moored by means of a bow hawser or by any othermeans which allows the vessel to rotate 360° around the mooring point. Generally, singlepoint mooring terminal can have two functions. Primarily, it affords a safe mooring to thevessels. Secondly, it can form a link in the transport of oil.

The single point mooring terminal can assume many forms. Of the more than 300 SPMsnow in use around the world (Maari, 1985) approximately 80 percent are of the type -single buoy catenary anchor leg mooring (CALM). CALMs have been employed asloading terminals since 1961. The CALM (Figure 6.35) basically consists of a cylindricalbuoy type float anchored to the seabed by a number of radial catenary chain legs (up toeight chains) while the vessel is moored to the buoy by one or more elastic synthetic(usually nylon) lines. This system employs the properties of the catenary to supply the

Berthing Structures


Fig.

6.3

6 C

aten

ary

Anc

hor

Leg

Moo

ring

(CA

LM

) Ter

min

al


512

elasticity required when holding large tankers in open seas. The buoy is cylindrical and canhave an outside diameter between six and twenty metres and a height between four andeight metres.

Single buoy, multi-leg mooring systems are the most commonly used offshore loadingfacility which has grown in significance in the recent years through the use of single pointmooring systems for the exploitation of marginal fields and in the development ofmoorings for deep water production facilities. One of the principle tasks of the designer ofcatenary moorings is to ensure that the system characteristics are such that the movementof the floating unit under extreme environmental conditions remains within acceptablelimits. Scrutiny of the calculation of catenaries show that chains with their high weight perunit length often have high energy absorption capacity. Whilst chain has this very desirableproperty of being a good energy absorbing catenary, it unfortunately suffers from that wellknown failing character, being only as strong as its weakest link. This constitutes thesecond major design criteria i.e., the tensile loads under extreme wave conditions shouldbe less than the proof loads.

The typical examples of different types of offshore loading systems are given below:

(a) Rotating manifold CALM system installed at Buchan, United Kingdom (Figure 6.36a )

(b) Soft yoke CALM system installed at Palanca, Angola (Figure 6.36b.)

(c) Rigid yoke CALM system installed at Cadlao, Philippines (Figure 6.36c)

Water depth can vary to a practical maximum of about 130 metres. Normal operating seastates with the tanker moored are the significant wave heights in the range of about fourmetres. High waves at a CALM terminal can generate prohibitive forces in the anchoringchains. This is especially the case where the ratio of maximum wave height to water depthis very high. CALMs have been installed in hostile areas such as North Sea with amaximum survival wave height up to 28 metres (Montrose Field) and the Enchora Field inBrazil with a maximum wave of 21 metres. Current velocity can be a limiting factor for thesubmarine hose system but CALM terminals have been installed and are operatingsuccessfully in currents of up to 2 m/s (four knots). Wind is not a significant factor becauseit only affects the SPM indirectly through forces applied on the tanker. Normal operating(with ship moored to the CALM) wind velocities are about 40 knots and design windspeeds are up to 70 knots.

Berthing Structures


(a) Rotating manifold type CALM system

(b) Soft yoke calm System

(c) Rigid yoke calm systems

Fig 6.36 CALM Systems


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Continuous motion of the buoy due to wave action results in wear and tear of the chains.The static tension in the chain is of the order of 50 to 100 kN. The static tension is afunction of surface angle the chain makes with the buoy, submerged unit weight of thechain and water depth. Increasing the static tension reduces the movements of the buoy andconsequently the wear of the chains but model tests have indicated that at this level ofstatic tension (50 to 100 kN) the mooring forces are kept to a minimum. For rough seacondition, however, survival of the CALM terminal may be of greater importance than theeffect of keeping mooring forces to a minimum. In such cases, an optimum must bedetermined between static tension, centre of gravity of buoy and wave spectra to minimiselinear and rotational movements of the buoy and consequently minimise possible damageto the oil cargo hose.

6.7.4 Importance in Indian Context

India’s coastline extends over 6000 km, which is the seventh largest coastline in the world.It has an exclusive economic zone of 2.02 million sq. kms, which is also the seventhlargest in the world. The prevailing environmental conditions viz., wave and wind climate,currents, air and sea surface temperature, salinity etc., at a specific location and their yearlyvariations are the most important inputs in the planning, design, construction and operationof offshore structures, coastal defence works, ports, ship routing and several other appliedocean research activities. Such data would also be vital for development of predictivemodels for forecasting of wave and wind climate of the ocean, ocean circulation, monsoonprediction, ship routing etc. Moored ocean buoys are considered the most appropriatesystem for measuring such data.

India has launched a comprehensive programme for exploration of crude oil from offshoreresources. Offshore activity is getting extended from west coast to east coast (Krishna,Godavari and Cauvery basins) where production wells have to be located at about 25 kmfrom the shore. Offshore loading systems are particularly attractive and economical forsmall offshore oil fields. As the offshore marine environment imposes severe demandsupon men, machinery and money, the research and development of buoy mooring systemsis an immediate necessity for the country.

6.7.5 Movement of Moored Tankers at Berth

Transportation of crude oil or refined products is the most important maritime traffic inthw world. Crude oil is transported in generally high capacity tankers. The movements oftankers at berth are an important design consideration for berthing structures. Modelstudies are used to predict the motion of ship and the forces on the mooring line for ships

Berthing Structures


berthed at an offshore jetty. (Sundaravadivelu & Natarajan (1996 a & 1996 b) The detailsof tankers, the types of mooring lines and the permissible movements of tankers are givenbelow:

6.7.5.1 Details of Tankers

The refined products are usually transported in smaller tankers less than 100,000 DWT.The main dimensions of tankers corresponding to the dead weight capacity and thedistribution of the tankers as on 1991 is given in Appendix 6.1 (PIANC working group24 Feb 1991).

6.7.5.2 Mooring Outfit

The mooring lines are handled by capstans, which are used to pull the lines and to tightenthe lines when the ship is moored. The different types of mooring line are

a) Steel wire

b) Polypropylene or nylon

c) Mixed rope i.e. a steel wire line connected to a short nylon lines(10 to 15m long)

The number, size and length of the mooring lines depend on the size of the ships.The mooring equipment on board is also given in Appendix 6.1.

6.7.5.3 Ship Motions

From the available data given in the literature, it is difficult to select precise figures onwhat could be the allowable movements of the ship. The values given below recommendedby PIANC (1971) is a good basis for safe mooring conditions.

Surge : ± 1.00 m Rolling : ± 2.5 deg

Sway : ± 0.75 m Pitching : ± 1 deg

Heave: ± 0.5 m Yawing : ± 1.5 deg

6.8 MONITORING OF INTEGRITY OF BERTHING STRUCTURES

In this section the Integrity Monitoring of the following berthing structures has beenpresented.


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(i) Mooring Dolphin

(ii) Failure of piles in a bulk berth

(iii) Forces measurement in tie rods

6.8.1 Mooring Dolphin

6.8.1.1 Condition of Dolphin

Consequent on the direct hit of a ship of 60,000 DWT fully loaded, the dolphin hasdeflected. It is observed that there is a level difference of the rigid 2.44 m thick pile cap by20 cm. In addition the central line of the front vertical pile had a displacement of 68.7 cmin one direction and 35.6 cm in the direction perpendicular to it. It is also reported thatthere is a twist of about 3° in bottom the axis on pile cap.

In pile No.1 (Vertical pile) just below the pile cap there is buckling of the steel casing ofthe pile. This failure appears to be due to excessive bending. The buckling is observed overa height of 15 mm and for a perimeter of 300 mm length. The maximum projection ofbuckling is 10 mm.

It is very clear that there is a rotation/displacement of the pile group. The pile cap can bereadily repaired and the original conditions can be reestablished. On the other hand, it isextremely difficult to assess the damages, if any, that might have occurred below the seabed level. According to analysis, under a horizontal force the point of maximum bendingare at the top of the pile. On the other hand, vertical piles are subjected to maximumbending and there is a damage to the vertical piles at the top. Furthermore, steel casings forthe vertical piles have not been provided upto full length.

6.8.1.2 Provision of Additional Piles

It is proposed that 4 vertical piles are provided at the 4 corners of the Mooring Dolphin asshown in Figure . These vertical piles shall go to the same founding level as the earliervertical piles. Further, it is necessary that these piles have the steel liner full up to thebottom as in the case of rakers.

6.8.1.3 Remedial Measures for Damage

The deck slab has spalling and cracking dolphin. There is also a consequential tilt of thesurface of the deck slab. Hence remedial measures suggested for the following 4categories of damage are :

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1. Opening of the joint between the concrete pile and the deck slab:

The workmen should thoroughly inspect the joint and the corresponding opening.Hence it is sufficient to pack the gap between the top of the pile and deck slab withEpoxy concrete mortar with the maximum size of the aggregate not exceeding 12 mm.The area around this pile junction where surface concrete has spalled off can becovered with Epoxy mortar from below the deck slab.

2. Treatment of corner pile exhibiting compression bulge:

The damaged concrete can be removed and the pile shall be repacked withM 30 concrete. The casing can be covered again with a steel plate of same thicknessas the original casing.

3. Spalling and cracking of concrete in the corners of the deck slab:

The concrete exhibiting spalling and cracking should be completely chipped offremoving all loosened debris and the reinforcement shall be exposed. The exposedsurface should be cleaned of all loose dust etc. and the deck slab should be refinishedwith M 30 concrete. It is desirable to use a shrinkage compensating additive in thefresh concrete.

4. Levelling of the top surface of the tilted deck (if required/desired):

The concrete surface is to be made very rough and the surface levelled again with afresh concrete of M 30 quality. For good bonding with the old concrete unless steelbars of old cap are extended into the new concrete whose thickness at places are150 to 200 mm, is necessary to provide a thick weld mesh or HYSD bar 2-wayreinforcing mesh in this new concrete and weld this on to the old reinforcement cage ata number of places.

6.8.1.4 Load tests for Adequacy of Mooring Dolphin

It is recommended to carry out horizontal load tests on the dolphin by means of wire ropes,pulleys and a turn buckle. Further they will strain-gauge the turn-buckly for measuring thepull as an additional check. Measurements to be carried out on the Dolphin are :

(a) Tilts/rotations of the Mooring Dolphin.


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(b) The displacements, in the horizontal plane of the Mooring Dolphin have to bemonitored with the help of theodolite.

6.8.1.5 Estimation of Relative Stiffness of the Damaged Mooring Dolphin

Natural frequencies of vibration of two identical mooring dolphins, one of them hit by acargo ship, were determined in order to estimate the extent of damage in comparison withthe other. 4 accelerometers were fixed on the top of the bollard at the centre of thedolphin.

Accelerometers 1 and 3 were connected to an on line signal analyser and 2 and 4 torecorders. Though the level of vibration at the maximum sensitivity of the accelerometerwas sufficient to record the resulting vibration patter, for greater accuracy the dolphinswere set to free vibration with the help of a tug. The auto spectral analysis of the vibrationsignals were done by the signal analyser and the results were displayed on the screen. Thefrequencies corresponding to the peaks in the auto power spectrum for the two dolphins arepresented in the following table.

Table 6.9 Frequency in Auto Power Specturm

Mooring DolphinFrequency in Hz

X YTrial Trial

1 2 3 Ave 1 2 3 AveDamaged 2.24 2.28 2.24 2.25 2.24 2.24 2.28 2.25Undamaged 2.64 2.68 2.64 2.65 2.52 2.52 2.52 2.52

Measurements were taken 3 times on both the dolphins and the average is given in table.

For a structure simplified as a single degree of freedom system the natural frequency isgiven by

m/K21fn π

= (6.51)

where K is the stiffness and m is the mass. Or the frequency is directly proportional to thesquare root of stiffness.

Berthing Structures


Since both the dolphins are identical in all respects, the mass can be taken to be same andtherefore their stiffness will be in the ratio of

7.023 : 5.063 - in the X-direction and

6.35 : 5.063 - in the Y-direction

The dolphin struck by the vessel has a reduced stiffness of 72 percent in the X-directionand 80 percent in the Y direction compared to the undamaged one.

6.8.1.6 Summary and Conclusions

Mooring dolphin (supported by 12 raker and 4 vertical piles) has been accidentally hit by afully loaded ship of 60,000 DWT and consequently dolphin has tilted. To restore themooring dolphin to its original capacity of 200 T horizontal force, the following measuresare recommended.

1. Repairing damages at the pile cap and pile interface.

2. Provide 4 additional vertical piles and make them integral with the existing mooringdolphin by suitably extending the pile cap.

3. Carry out load tests by pulling the Mooring Dolphin against each other upto 200 T andmonitoring the performance, as a final confirmation of the restoration to its ratedcapacity

6.8.2 Failure of Piles in a Bulk Berth

Investigation on the possible causes of failure of pile of a bulk berth is disumed in thechapter. The causes of failure, its impact on the behaviour of the overall structure andremedial measures required are investigated.

6.8.2.1 Brief Description of Failure of Pile

The following weather conditions occurred nearer to the pile on that day of failure.

Wind - Mainly westerly 18 to 22 knots

Weather - Fair

Sea - Moderate to rough

Swell height - 1.8 to 2.2 metres


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In Pile P1 and 11 steel liners have fallen and 9 liners are inclined. The pile P2 has alsotitled. The concrete pile P1 was broken at 40 cm below the bottom of steel liner with ashape of sphere. 3 number of main reinforcement bars out of 14 in total were observedsnapped at broken concrete face and the balance 11 bars were slipped out of concrete(Figure 6.42 ).

The detailed of studies were carried out on the following aspects.

1. Estimation of wave and current forces

2. Estimation of foundation capacity of piles

3. Estimation of structural capacity of piles4. Measurement of frequency response on freshly concreted and set piles.

During the construction of the piles, initially the steel casing of pile and subsequently thepiles themselves are free cantlevers (as they are not braced at top) subjected to wave andcurrent forces.

Fixity to the cantilever initially comes from the soil surrounding the casing pipe and laterfrom the soil layers around the casing and the pile below. In the case of pile P1 and P2, theclay layer thickness is only about 3.5 m and 2.6 m respectively as against an averagethickness of 4.5 m at other locations. As the casing stops at the top of the rock layer, theultimate moment resistance of soil is about 15.5 T.m only. This moment can be caused by0.84 T of lateral force at +3.0 m level. This force can be caused by a current of 3 knots. Inreality, waves and currents can act in unison and therefore even under medium weatherconditions the moment on the casing pipe will exceed the moment resistance of the soil.This is also confirmed by the reported failing or tilting of several steel liners.

After the pile is concreted, with external moment greater than the resistance from soft clay,bending stresses will be transferred below the bottom of the casing i.e., to fresh concrete.This is particularly true in case of pile P1 and P2. The natural frequency of freshlyconcreted pile is only about 1/3 of well set piles and will be nearer to the wave frequencyresulting in dynamic amplification of the forces. Under such circumstances even if thepile may not fail (the external moments within ultimate limit) the concrete will not gain itsfull strength, in particular bond between the reinforcement and concrete at bottom will beaffected. The ultimate structural capacity of the pile based on the bond stress that can bemobilised after 1, 7, 14 and 28 days are 15.3, 34.8, 44.8 and 50.0 T.m respectively. Thismeans that even during the process of concrete gaining strength, the same is continuously

Berthing Structures


being subjected to stresses due to waves and currents. These stresses could be well beyondpermissible stresses resulting in partial bond failure.

The partial bond failure has happened in case of piles P1 and P2, particularly in view of thebending stresses transferred below the bottom of the casing i.e. to fresh concrete due toinadequate ultimate soil capacity around the casing. In other words even after the 28 daysof setting, they were substantially weaker as compared to a full strength pile. Therefore,somewhat higher waves than normal, combined with effects of wave reflection andcurrents, has resulted in failure. The weakened piles will also have higher periodcompared to an integral pile. In such a case, the dynamic amplification factor of waveforces will much higher, resulting in failure of the pile.

6.8.2.2 Simplification to Safety of Structure

In the light of the above discussions it cannot be ruled out that other piles in the regionduring the process of concreting and subsequently have been weakened at the bottom..This has the following simplifications:

The piles will not have full fixity at the bottom and in the extreme case behave as a hinge.This will in turn affect the structural behaviour of berthing structure.

(a) Under horizontal forces.

(b) Buckling behaviour of the pile under axial loads.

This means that for the design of berth under consideration, if the piles are assumed ashinged at bottom, there may not be much of a consequence.

6.8.2.3 Recommendations arising out of Study for Future Construction

Whenever piles of this type are installed using this technique, the following is to beadopted (Sundaravadivelu et al. (1993)).

1. The steel liner for the pile should have sufficient embedment into the soilstrata such that the soil surrounding the casing will offer adequate resistance.

2. The casing should be braced at top against a firm support (and not anothercasing pipe or a freshly concreted pile).


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3. The braces must be above high water level to avoid current and wave forces onthe braces, otherwise the whole system has to be designed for the wave currentforces on the braces as well.

6.8.3 Force Measurements in Tie Rods

6.8.3.1 Brief Description of Berth

The typical cross section of the berth is given in Figure 6.37. The structural arrangementof the system consists of 1100 mm thick main diaphragm wall connected by 80 mm diaanchor rods at approximately 1500 mm c/c. In addition, the 1100 mm thick diaphragmwall is connected to two 1000 mm dia vertical piles by a rigid deck consisting of 3850 mmdeep cross beam. Considering the rigidity of the deck system and capacity of 1000 mm diapiles to resist lateral load and the flexibility of the 80 mm dia tie rod, most of the lateralload will be transferred to the 1000 mm dia vertical piles. In order to verify the above , itis recommend to measure load transferred to the tie rod after dredging is completed i.e.when the tie rod is meant to transfer the horizontal force due to active earth pressure onfront diaphragm wall to the deadman diaphragm wall.

The details of the tie rod force measurements are given in Sundaravadivelu et al. (1990)and a brief description of force measurement is given below.

Berthing Structures


Fig.

6.3

7 T

ypic

al C

ross

Sec

tion

of a

Ber

th


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6.8.3.2 Installation and Measurement of Forces in Tie Rods

Load Cell:

Three locations were selected for installation of strain gauge type load cells. The straingauge type load cells were selected considering various factors like

- Economy

- Time available for installation

- Ease of measurement technique to be adopted at site etc.

Pretension of Tie Rod:

As a part of the construction scheme a pretensioning of all the tie rods was done asfollows. Two hydraulic jacks were used to give a pretension of about 3 to 3.5 T. Thetightening nut introduced before pretensioning was then first hand tightened. Then a pipewrench of length 1 m was used to tighten the nut further. After this a check nut wasintroduced and tightened.

Installation of the Load Cells:

The same procedure as adopted for pretensioning the tie rod was used here also afterplacing the load cell, between the outer face of Deadman diaphragm wall and the nut.

Measurement of Pretension:

The two cables of the load cell were connected to strain measuring unit DMD 29 (HBM,West Germany) and the reading corresponding to no load condition was measured. Thereadings after pretensioning the tie rod was also measured. The results obtained aretabulated below in Table 6.10.

Table 6.10 Measured Strain before and after Pre-tensioning of Tie Rod

Location AStrain (Units of DMD Display)

Bridge 1 Bridge 2Reading corresponding to No load 1427 641Reading after pretension 1764 1090Difference in reading 337 449

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Corresponding Loads 8.408 T 10.496 TAverage Load 9.452 T

Though only a 3.5 T pretension was given using a jack, the tightening of the nut with thehelp of a wrench introduced an additional load of about 6 Ton in the rod.

The measured load was once again verified by releasing the load on the cell with the helpof hydraulic jacks. It was found that the pressure gauge of the jack showed a load of9.57.T

The same procedure was adopted for installation of the remaining two load cells. But thepretension was not measured for these two tie rods.

6.8.3.3 Measurement of Tie Rod Forces after Dredging

Though it was originally considered to measure the load at different stages of dredging,because of some practical difficulties, only one reading was taken after dredging to therequired depth of -11m.

Initially, all the strain gauge bridges were checked for its functioning. It was found that ofthe 6 bridges for which cables were available outside, only one bridge of cell 1 installed atlocation 85 was not functioning as some water has gone inside the cable. Measurementswere taken for the remaining 5 bridges and the bridge for which the cable was terminatedon the outer cover of the cell was left undistributed because any attempt to open it wouldcause water entering the cell (During measurement there was atleast 2 feet of water abovethe cell and continuous pumping of water was required to do the measurements).

Mechanical jacks were introduced to release the load from the cells and readings of thebridges were taken one after the other for loaded and unloaded conditions.

6.8.3.4 Summary of Results

From the preliminary measurements, it has been found that a pretension of 9.5 t is given toanchor rods instead of what was thought to be around 3.5 t. This however, do not in anyway affect the behaviour of the soil-structural system. In fact, a higher pretension is betterto keep the anchor rod tact.

Result of the final load measurement shows that after dredging to a level of -11m, load inthe anchor rod has increased only marginally by about 3 to 3.5 tons in locations A and B.


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The load measured in location C shows a marginal reduction, taking for granted that thepretension here was also of the order of 9.5 T. This, however, cannot be ascertainedbecause pretension at this location was not measured during installation. (It may be pointedout here that the pretension was only a factor of the strength of the people who applied thetension using the wrench). The small difference in measured load by the two differentbridges of same load cell is due to the eccentricity in loading which is characteristic of loadtransfer through screws. Small eccentricities are unavoidable in field situations, in spite ofprovision of spherical seating in the load cells.

6.8.3.5 Conclusion

1) It has been possible to monitor the forces in the rod using load cells as adopted.All the cells performed well 6 months after installation in spite of severeenvironmental conditions like full submergence in sea water.

2) The total tie rod forces even after dredging to -11.0 m level are between7 to 13 T, as against an estimated permissible value of about 65 T from structuralconsideration for tie rod. This includes pretension force upto 9 T. Without thispretension the tie rod forces would have been even less.

6.9 SELECTION OF TYPE OF BERTHING STRUCTURE

A Berthing structure is usually constructed to serve a definite use. The purpose of it is tohandle passengers or general cargo or a combination of both or it may be required tohandle a specific type of cargo, particularly bulk cargo such as oil, ore, cement, and grainsor to handle containers. The type of berthing structure depends upon the purpose of theberth, size of ships that use the berthing structure, the direction of the wave, wind andsubsurface soil conditions, in particular the depth of the bed rock or firm bearing materialand the water depth.

The selection of type of berthing structure also depends on the magnitude and nature ofloading, hydraulic conditions such as wave action and currents. Fire hazard and safetyrequirements, damage susceptibility and ease of repairs, environmental and regularityconcerns over water circulation and habitat loss always favour open type construction.

Closed type construction generally offers greater horizontal and vertical load capacity andimpact resistance than the open piled construction. The vertical face of a closed type ofconstruction reflects wave energy, if the structure face is exposed to significant waveaction. The possible scouring at the face of the closed type structure due to current action

Berthing Structures


influences the choice of the type. If all factors considered for selection of the type ofberthing structure remain the same the long-term maintenance govern the type of berthingstructure.

When a berthing structure has to be constructed in shallow water or on existing land inconnection with the dredging of a harbour basin, a vertical face type structure such as thediaphragm wall is very competitive. The presence of bedrock or hard strata below thedesign depth of water favours the vertical type.

The vertical face type structures will be preferred when tension piles fail to penetrate tosufficient depth due to hard layers. When the existing water depth is close to the desireddredge depth then this type of structure is suitable. When dredging is expensive and whenweak and soft sediments endanger the overall stability, then open type structures areadopted.

As a general rule vertical face construction such as diaphragm wall is favoured wherewater depths are shallow to moderate. Anchored bulkheads require some minimumembedment depth and these bulkheads are practical and economical to wall heights uptoabout 10 m. At deep water locations with soft soils extending relatively deep below themud line then pile foundations are provided. Even though open pile supportedconstruction is used at shallow rock locations, the cost to anchor the piles to the bed rockand to provide adequate horizontal stability usually exceeds that of a suitable vertical facetype structure.

Relieving platforms, which are a combination of open type and fill type construction, maybe used to provide uplift resistance thereby improving the lateral load resistance of thepiles. A relieving platform also reduces the required bulk head wall height thus extendingthe water depth capability of the system.

When the slope of the bottom is so steep that a jetty or a pier cannot be projected out fromthe shore without having the outshore end in water so deep, then foundations are eitherimpractical or very expensive. In such conditions a wharf or quay is suitable andeconomical.

For bulk cargo berth, open type constructions with approach trestle is preferable. Oildocks and some forms of bulk-handling cargo docks are of lighter construction thangeneral cargo-handling docks, as they do not require warehouses, nor do they have tosupport rail, road tracks or extensive cargo-handling equipment. Since the main productshandled over oil docks are usually unloaded at fixed points and transported by pipelines,


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the required area of solid deck is very much reduced, as are width and length of the dock,if supplemented by dolphins to take the bow and stern mooring lines. For this reason, afull-length pier or wharf is not economical or essential, and the use of larger and deeperdraft tankers has resulted in the adoption of the fixed mooring berth. This type ofconstruction is economical because the large mooring forces imposed on the dock by thelarge ships shall be concentrated at single points. The pull of the mooring lines can betaken by dolphins off the bow and stern of the vessel and by breasting dolphins on bothsides of the fixed platform. The breasting dolphins also keep the ship away from theplatform and take the impact of the ship while docking.

In some locations, it is impossible or uneconomical to provide a pier, wharf or fixedmooring depth owing to site conditions or the deep draft of some of the recentlyconstructed supertankers and ore carriers. In such cases an offshore mooring may beprovided and the cargo transferred to the shore either by lighters, long conveyors,ropeways or by submarine pipeline, if the product is a liquid such as oil, gasoline andmolasses.

Direction of waves and wind may have a bearing on the type of dock selected. In general,the dock should not be broadside to the prevailing wave front. If the terminal is in exposedlocation, and the wave front is parallel to the shore, a wharf type of dock may have to beruled out. Also, all things being equal, it is better to have the ship anchored parallel to thedirection of prevailing winds or if this cannot be accomplished, the ship shall be anchoredin such a way that the wind is holding the ship off the dock.Soil conditions will have an important bearing on the type of dock selected. The bottommay be more favourable in the region close to the shore, thereby favouring a wharf orbulkhead installation. However, rock may be encountered which would make it verycostly to obtain the required depth of water along the dock. In such a case, a pier with anapproach trestle or mole may be the solution to eliminate the need for costly excavation.

6.10 DESIGN OF DIAPHRAGM WALL

6.10.1 General Remarks

The definition of various structures such as dock, wharf, quay, jetty, etc. are given below:

A dock is the most general designation for a structure or place at which a vessel can bemoored. A wharf is a dock structure built nearly parallel to the coast and continuous withthe shoreline, so that it also performs as a soil retaining structure. It is also called quaywhen it is of solid fill vertical wall construction and is long and continuous. Wharves and

Berthing Structures


quays are backed by warehouses, marshalling and storage areas, industrial areas, roads,rails, etc., which are often created by extensive fill operations. A pier or jetty is a dockstructure, which projects out into the sea. Because of its geometry, it can be used forberthing of vessels on three sides. It does not necessarily run perpendicular to the shoreline or wharf line but may project under any angle. It may also be connected to the shoreor wharf line by a trestle and thus become T or L shaped jetty or pier. Moles or trestles areprimarily pier or platform access structures, used for vehicular, pipeline, conveyor andsidewalk. Moles are of solid fill construction and trestles are of free standing pile bents orpile groups with bridging structure spanning them.

Dolphins are isolated structures used mainly to absorb the impact of berthing ships referredto as breasting or berthing dolphins and to serve as a point for securing a vessel’s mooringlines, referred to as mooring dolphins.

A fixed mooring berth is a marine structure consisting of dolphins for tying up the vesseland a platform for supporting the cargo handling equipment.

A sheet pile wall comprises of a row of piles interlocking with one another so as to form acontinuous wall to be used as earth retaining structure.

Diaphragm wall is a vertical wall structure classified as a cantilever or tie back system.The tie back system can be a tie rod with a deadman or a combination of vertical and rakerpiles or only vertical piles.

A relieving platform consists of a low level pile supported deck that is filled over in orderto gain stability and relieve pressures behind the wall in weak soil conditions.

Gravity wall consists of cut stone blocks or concrete blocks placed on top of each otherand capped with a massive concrete wall or a concrete caisson monolith. Gravity wallsgain stability against sliding and overturning by means of its weight, proportions and soilfriction.

6.10.2 Example

A cantilever type diaphragm wall of 5.0 m panel length is proposed for the fishing jetty.The reduced level of the ground varies between +1.60 m and 2.40 m. The cut-off level ofthe diaphragm wall is +1.0 m and the top level of the deck is +2.25 m.


530

The diaphragm wall is proposed for the quay wall at +2.25 m and founding level isassumed at -8.0 m. Dredge level is -2.20 m. The total height of wall is 10.25 m.

The passive pressure and active pressure acting on the wall is calculated based on the soilproperties from the boreholes. Above the dredge level(i.e. above -2.20 m) the properties ofthe soil considered are N = 10, φ = 300, δ = 200 and ka = 0.297. Below the dredge level,the properties considered are N = 20, φ = 330, δ = 220, ka = 0.264 and kp = 8.08. Thesurcharge of 10 kN/m2 is also assumed on the landside of the wall.

The quay wall is analysed as a two-dimensional structure using SAP90 (StructuralAnalysis Programme 90). The discretization showing node numbers and element numbersof diaphragm wall is shown in Figure (6.38) For analysis, 1 m width of diaphragm wall isconsidered. The load acting at each node is shown in Figure (6.39). Below the dredgelevel, sea side springs are provided at each node and the values are shown in Figure (6.40)The first iteration indicates that the force coming on the springs at the node numbers 10,11&12 is more than the passive resistance. Hence these springs are replaced with actualpassive resistance at that location and the second iterative analysis is carried out. Theiteration is continued till the forces on each spring is less than the passive resistance. Thebending moment diagram and shear force diagram are shown in Figure 6.41(a) andFigure 6.41(b) respectively. The reinforcement details of diaphragm wall is shown inFigure 6.42.

6.10.3 Design of Quay Wall

Limit state method is used for the design of quay wall.Grade of concrete : M30

Steel reinforcement : Fe415

Thickness of quay wall : 500 mm

Clear cover provided : 75 mm

Section AA (From -2.5 m to -5.5 m)

Maximum Bending moment : 432.42 kN/m

Load factor as per IS 4651 for earth pressure : 1.0

Effective depth : 500 - (75+ 28/2) using Y - 28 bars

: 411 mm

Berthing Structures


Fig.6.38 Discretisation Showing Node NumbersAnd Element Numbers


532

Fig. 6.39 Load Acting At Each Node

Berthing Structures


Fig.6.40 Loads on Land Side and Springs on Sea SidekN/m


534

Fig.

6.4

1 (a

) Ben

ding

Mom

ent D

iagr

am

Fig.

6.4

1 (b

) She

ar F

orce

Dia

gram

Berthing Structures


Fig.6.42 Reinforcement Details of Diaphragm Wall


536

2bdMu = 2

6

411X100010X42.432 (Considering one metre width)

From SP 16, = 2.55

Pt = 0.794

Ast = 0.794 x 5000 x 411 (for 5 wide panel)

= 16317 mm2

Provide 21 nos Y - 28 + 21 nos Y - 20 on earth side for 5 m wide panel

Ast provided = (21 x4π x 282) + (21 x

4π x 202)

= 19,509 mm2 (0.78%)Ast min = 0.2/100 x 5000 x 411

= 4110 mm2

Provide 21 nos Y-16 on the seaside

Ast provided = 4221 mm2

Section BB (From + 2.25 m to -2.5 m and from -5.5 m to -8.0 m)

Maximum bending moment = 267.32 kN/m

2bdMu = 2

6

411x100010x32.267 (for one metre)

From SP 16, = 1.58

Pt = 0.475

Ast = 0.475 x 5000 x 411 (for 5 m wide panel)

= 9761 mm2

Berthing Structures


However provide 21 nos Y-28 (12931 mm2 ) on T-16 on seaside for 5 m wide panel

Design for shear reinforcement:

Maximum shear force = 187.82 kN

Nominal shear stress, τ γ =411x10001000x82.187

= 0.46 N/mm2

Permissible shear stress τ c = 0.59 N/mm2 (for 0.78%steel)

τ γ < τ c

Therefore provide nominal reinforcement only

Provide 6 legged Y - 10 stirrups at 150 mm c/c as nominal shear reinforcement and Y - 10stirrups at 300 c/c (Fig. 6.49)

v

sv

bxSA =

150x1000

10x4

x6 2π

yf4.0 = 9.6 x 10 4−

v

sv

bxSA >

yf4.0 Hence O.K.

6.11 DESIGN OF DOLPHIN

6.11.1 Layout of Berthing Dolphin

A typical plan and cross section of berthing dolphin are given in Fig.6.50. The dolphinconsists of a deck slab of size 12 m x 21 m and 1500mm thick and supported over 15numbers of vertical concrete piles each of 1500 mm diameter. Piles are braced at +2.0 m .The beam is of size 1500 x 1500 mm in longitudinal as well as transverse direction. Afender beam is provided from bottom of the deck to +0.5 m level. The thickness of the


538

beam at deck level is 1000 mm and is reduced to 500 mm at +0.5 m level. The dredgelevel of dolphin is kept at -16.50 m and piles have been taken upto -30 m below theseabed.

6.11.2 Loads

The loads and load combinations considered in the design of berthing dolphin are asfollows:

6.11.2.1 Dead Load (DL)

Self-weight of the structure plus superimposed loads of a permanent nature.

6.11.2.2 Live Load (LL)

Dolphins are designed for a UDL of 10 kN/m2

6.11.2.3 Force on Berth (BF)

The berthing force of 2785 kN per fender is considered for the 45000 DWT vessel withSVC 2000 H (RS) type fender.

6.11.2.4 Mooring Force (MF)

The bollard pull of 1000 kN per bollard is considered and is applied at above deck level.Bollard forces are considered to act in any direction with in 1800 around the bollard in thehorizontal plane.

6.11.2.5 Wave Force (WF)

Wave load due to 1.8 m wave height is considered on piles with marine growth of 50 mmon the radius of piles.

6.11.2.6 Current Force (CF)

Current load due to a maximum current of 0.5 m/sec is considered.

6.11.2.7 Seismic Force (SF)

The horizontal earthquake force shall be calculated for Dead Load + 50% of live load. Theimportance factor of 1.5 are considered.

Berthing Structures


6.11.2.8 Load Combinations

The following load combination is considered in the analysis.

1. DL + LL +BF + WF + CF

2. DL + LL +MF + WF + CF

3. 1.5DL + 1.5LL +1.5BF + 1.0WF + 1.0CF

4. 1.5DL + 1.5LL +1.5MF + 1.0WF + 1.0CF

5. 1.2DL + 1.2LL +WF + CF + 1.5 SF

6. 0.9DL + 0.9LL +WF + CF + 1.5 SF

6.11.3 Analysis

Analysis is carried out using SAP 90 by idealizing dolphin deck using shell element andpiles by beam elements.

6.11.4 Design

The deck slab is designed as flat slab. The design of piles have been carried out using limitstate method. M30 grade concrete and Fe415 grade of steel are considered in the analysisand design. The design is also checked against limit state of serviceability. The clearcover considered in the design are as following:

Piles : 75 mm

Beams : 50 mm

Deck Slab : 40 mm

6.12 DESIGN OF PILES

Grade of concrete to be used : M30

Grade of steel : Fe415

Diameter of pile D : 1500 mm


540

Unsupported length of pile : 28.25 m

Effective length : 1.2 x 28.25

l eff : 33.90 m

l eff /D : 33.90/1.5

: 33.90>1.5

Therefore design as a slender member

Eccentricity

e min =30D

5001

+

=30

1500500

1000x25.28+

= 106.50 mm

From SP 16 (Table 1),

For l eff /D = 33.9.6 e/D = 0.26Therefore e = 0.26 x 1500 mm = 390 mm

Maximum factored moment = 7510.76 kN/m(Member 60)

Corresponding factored axial force P u , = 1644.91 kN (Compression)

Moment due to eccentricity = 1644.91 x 0.39 = 641.52 kNm

Total moment, M u , = 8152.27 kNm

Providing a clear cover of 75 mm,D

'd = 0.05

Berthing Structures


2ck

u

DfP = 2

3

1500x3010x91.1644

= 0.024

3ck

u

DfM = 3

6

1500x3010x8152

From chart 55 of SP 16

P/f ck = 0.08

P = 0.08 x 30 = 2.4

A st = x4

x100

4.2 π 15002

= 43,430 mm2 (2.5%)

provide = 54 432 mm2

Ties: Provide Y - 10 rings at 250 mm c/c


542

REFERENCES

Agerschou, H., Lundgren, H., Sorensen, T., Ernst, T., Korsgaard, J., Schmidt, L.R. andChi, W.K., (1983). “Planning and Design of Ports and Marine Terminals”, A Wiley-Interscience Publication, 220-225.

Bathe, K.J., Wilson, E.L and Peterson, F.E. (1978). “SAPIV: A structural analysis Programfor static and dynamic response of 4651 linear system”, Report EERC 73-11Univ. ofCalifornia, Ber Kely.

Berteaux, H.O., (1976). “Buoy Engineering”, John Wiley & Sons, New York.

Bruun, P., (1981). “Port Engineering”, Gulf publishing company book division, Hudson,Texas.

Faltinsen, O.M., Kjaerland, O Liapis N and Walderhaug H. (1979). “HydrodynamicAnalysis of Tankers at Single Point Mooring Systems”, Proceedings of SecondInternational Conference on Behaviour of Offshore Structures, London, PP.177-206.

Gaythwaite, John. (1990). “Design of Marine Facilities for Berthing”, mooring and repairof vessels, Van Nostrand Reinhold, New York.

IS 2911 Part IV (1979). “Indian Standard Code of Practice” for design and construction ofpile foundation.

IS 456 (1978). “Indian Standard Code of Practice” for Plain and Reinforced concrete.

IS 875-1984. “Indian Standard Code of Practice for structural safety of Buildings”, WindLoad Constructions, BIS, New Delhi.

IS-4651 Indian standard Code of practice for planning and design of ports and harbour,Bureau of Indian Standards, New Delhi.

Part 3 (1974) - LoadingPart 4 (1989) - General Design considerationsPart 5 (1980) - Layout and Functional requirements

Langeveld, J.M. (1974). “Design criteria for single point mooring systems”, Journal ofWaterways,

Manohar, S.N., (1964). “Charts for the Design of Eccentrically Loaded Circular Columns”,Indian Concrete Journal.

Maari, R., (1985). “Single Point Moorings”, SBM Inc. Publications, Monaco.

Berthing Structures


Nakajima, T., Motora, S and Fujino M. (1982). “On the Dynamic Analysis of Multi-mooring Lines”, Proceedings kof Fourteenth Annual Offshore Technology Conference,OTC 2212, Texas, pp.679-702.

Per brun (1983). “Port Engineering” Gulf Publishing Co.

PIANC (1991). “Movements of Moored Ships” and berthing Pianc working groups 24.

Pinkster, J.A and Remery, G.F.M. (1975). “Role of Model Tests in The Design of SinglePoint Mooring Terminals”, Proceedings of Seventh Annual Offshore TechnologyConference, OTC 2212, Texas, pp.679-702.

Quinn, A.D. (1961). “Design & Construction of Ports and Marine Structures” McGrawHill Book Co.,

Raju, V.S., and Sundaravadivelu, R and Gandhi S.R., "Analysis of alternative systems fora berthing structure", First National Conference in Docks and Harbour Engineering, IIT,Bombay, Vol. I, December 1985, pp B195- B206.

Ranga Rao, A.V and Sundaravadivelu, R. (1992). "Non-linear Soil Structure Interaction ofberthing Structures", National Seminar on Offshore Structures, Docks and Harbours,Roorkee, October 16-17.

Ranga Rao, A.V and Sundaravadivelu, R. (1994 A). "Effect of Configuration of piles inDolphin", National Seminar on Design of Pile Group and Pile Cap, Indian GeotechnicalSociety, Madras.

Ranga Rao, A.V and Sundaravadivelu, R. (1994 A). "Computer Aided Design of BerthingStructures", INCHOE - 94, Pune, Vol I, pp B87-B96.

SP: 16 (S&T) (1980). “Design Aids To Reinforced Concrete” IS: 456-1978.

Srinivasan, R and Rangwala, R.S.C. (1991). “Harbour, Dock” and Tunnel Engineering.

Sundaravadivelu, R., Idichandy, V.G., Gandhi, S.R. and Raju, V.S. (1990). "Tie rod forcemeasurements in a Cargo Berth", Journal of Waterways, Port, Coastal and OceanEngineering, ASCE, Vol.116, No.1, pp 43-56.

Sundaravadivelu, R., Raju, V.S. and Idichandy, V.G. (1993). "Failure of OffshoreConcrete Piles During Construction", Third International Conference On Case Histories inGeotechnical Engineering, St. Louis, Missouri.

Sundaravadivelu, R., and Ranga Rao, A.V. (1996). "Expert System for Estimation ofForces on Berthing Structures", International Conference in Ocean Engineering, ICOE'96,pp 393-397.


544

Sundaravadivelu, R., and Natarajan, R. (1996). "Model Studies on Moorings of A LPGTanker Berthed At An Offshore Jetty", The fourth Pacific/Asia Offshore MechanicsSymposium., Korea, Oct. 31- Nov.2.

Sundaravadivelu, R, and Natarajan, R, (1996). "Experimental Investigation on Open SeaBerthign of a LPG Tanker", First Asia - Pacific Conference on Offshore Systems: Mobileand Floating Structures, Malaysia, 10-11.

Supplement to Bulletin N 45 (1984). “Report of the International Commission forImproving The Design Of Fender Systems”, Permanent International Association ofNavigation Congresses.

Webster, R.L. (1980). “On The Static Analysis of Structures with Strong GeometricNonlinearity”, Computers and Structures, Vol. 11, pp.137-145.

Wichers, J.E.W. (1979). “Slowly Oscillating Mooring Forces in Single Point MooringSystems”, Proceedings of Second International Conference on Behaviour of OffshoreStructures, London, pp.661-692.

Woodruff, G.B. (1963). “Berthing & Mooring force”, Tr. ASCE, Vol. 128, Part IV.

Berthing Structures


NOTATIONS

a’ - The Distance from the Compression Face to the Point of the Crack

acr - Distance from the Point Considered to the Surface of the NearestAst - Area of Tensile SteelAst - The Area of Tension SteelAsv - Total Cross Sectional Area of Stirrup LegsAw - Windage Area (m2)Ax1 - End on Projected area of VesselAy - Side Projected Areas of Vesselb - Breadth of the Sectionbt - The Width of the Section at the Centroid of the Tension SteelB - Beam of the Vessel in (m)C - Effective CoverC1 - Coefficient for the Area of Stress BlockC2D - Distance of the Centroid of the Concrete Stress Block, Measured

from the Highly Compressed EdgeCb - Shear Strength of the Rock at Pile BaseCc - Compression in Concrete SegmentCc - Berthing Configuration CoefficientCcXc - Moment of Compression in ConcreteCcXsc - Moment of Compression of Steel About the Center LineCd - Deformation Co-efficientCD,CM - Drag, Intertia Coefficient (Figures 6.19 to 6.21)CDx, CDy - Drag Coefficients Along x, y DirectionsCe - Eccentricity CoefficientCg - Geometric CoefficientCm - Mass CoefficientCmin - Minimum Cover to the Longitudinal BarCS - Softness CoefficientCs - Average Shear Strength of Rock Along Rock SockerCs - Compression in Steel ReinforcementCw - Shape Factor = 1.3 to 1.6Cw - Crack WidthCym - Yaw Moment Coefficientd - Water Depth (m)dc - Effective CoverD - Diameter of Pile (m)


546

D - Overall Depth of the MemberDL - Average Light Draft (m)DM - Moulded Depth (m)E - Berthing Energy in (T- m)Ec - Modulus of Elasticity of Concretefa - Allowable Frictional Resistancefcbc - Calculated Bending Compressive Stress in Concretefcc - Calculated Direct Compressive Stress in Concretefci - Stress in Concrete at the Level of ith row of Reinforcementfn - Natural Frequencyfs - Service Stress in Tension Reinforcement Which may be Taken asfsi - Stress in the ith Row Of Reinforcement, Compression Being

Positive and Tension being Negativefst - Stress in Steelfy - Characteristic Strength of the StirrupF - Force Due to Wind (kg)F - Factor of Safety Taken as 3.0FDM - Total Drag Force on A Vertical Pile From the Sea Bottom to the Surface Crest Elevation (N)FIM - Total Inertial Force on a Vertical Pile from the Seabed to the Free Surface Elevation (N)FM - Maximum Value of the Combined Drag and Inertial Force, (N)Fn - Horizontal Series ForceFwx - Longitudinal Wind ForceFwy - Lateral Wind Forceg - Acceleration Due To Gravity in (m/sec2)h - Depth of the SectionH - Wave Height (m)imin - Least Radius of GyrationI - A factor Depending Upon the Importance of the StructureK - StiffnessKDM - Drag Force FactorKIM - Inertial Force FactorL - Length of the Vessel in (m)Lν - Length Between Perpendicular (m)l - Distance from the Centre of Gravity of the Vessel of the Point of

Contact Projected Along the Water Line of the Berth In (M)lef - Effective Length of Column (pile)leff - Effective LengthLOA - Overall Length of Vessel

Berthing Structures


m - Virtual (mass + added mass) Mass of Vesselm - Modular Ratiom - MassMDM - Moment on Pile About Bottom Associated with Maximum

Drag Force, (N, m)MIM - Moment on Pile About Bottom Associated with Maximum

Inertial Force (N, m)MM - Maximum Total Moment (N, m)Myw - Yawing Momentn - Number of Rows of ReinforcementNc - Bearing Capacity Factor Taken As 9.0P - Wind Pressure (kg/m2)Pi - (Asi/bD) where Asi is the Area of Reinforcement in the ith rowqa - Allowable End Bearing Pressurer - Radius of Gyration of Rotational Radius on the Plane of

the Vessel (m) Reinforcementsv - Spacing of the Stirrups Along The Length of the MemberSD - Effective Lever Arm for FDM from the Bottom of Pile, (m)SDM - Drag Force Moment ArmSIM - Inertio Force Moment ArmTXst - Moment of Tension Insteel About The Center Line.T - Tension is Steel Reinforcementu - Translatory Velocity of Shipv - Berthing Velocity (m/s)w - Unit Weight of Sea Waterx - Depth of Neutral Axisyi - Distance From The Centroid of the Section to the ith row of theV - Berthing Velocity in m/secV - Shear Force Due to Design LoadsV - Velocity of Vessel (m/s), Normal to the BerthVs - Strength of Shear ReinforcementW - Unit Weight of Water (1.03 tonnes/m2 for sea water)WD - Displacement Tonnage of the Vessel (in tones).Wm - Weight of Mass Under Consideration.α - Shaft Adhesion Factor Taken as 0.3.αm,φm - Coefficient Read from the Figures 6.10 to 6.17αn - Design Horizontal Seismic coefficientαo - Basic Horizontal Seismic Coefficient Based on the Zoneβ - A Coefficient Depending Upon the Soil-Foundation System


548

θ - Wind Direction or Angle of Attackρ - Mass Density of Sea Water = (w/g) = 1025.2 kg/m3

φ - Diameter of the Reinforcing Barω - Angular Velocity of Shipε1 - The Strain at the Level Considered Ignoring the Concrete in

the Tension Zoneτc - Design Shear Strength of the Concreteσcbc - Permissible Bending Compressive Stress in Concreteσcc - Permissible Axial Compressible Stress in Concreteεm - Average Strain at the Level Consideredτr - Nominal Sheer Stressσs - Stress in Tensile Steel

Berthing Structures


APPENDIX 6.1

SIZES OF PASSENGER SHIPS, FREIGHTER, TANKERS, ORE CARRIERS ANDFISHING AND FISHING VESSELS

A.6.1.1 BULK CARRIERS

Dead WeightTonnage (Tons)

OverallLength (m)

Width (m) Height (m) Fully LadenDraught (m)

4000 100.0 15.4 7.0 6.36000 118.0 16.6 8.3 6.98000 130.0 17.6 9.5 7.4

10000 140.0 18.5 10.5 7.912000 150.0 19.4 11.2 8.515000 163.0 20.7 12.0 9.020000 180.0 22.8 13.0 9.725000 194.0 24.7 13.8 10.330000 205.0 26.5 14.3 10.740000 223.0 29.7 15.4 11.150000 235.0 32.5 16.2 11.360000 245.0 35.0 17.1 12.080000 259.0 39.2 18.8 12.6

100000 268.0 42.5 20.4 13.0

A.6.1.2 COMBINATION BULK/ORE CARRIERS (100,000 DWT NOMINAL)

Dead WeightTonnage(Tons)

OverallLength

(m)

Breadth(Moulded)

Depth(Moulded)

Draught(Loaded)

Draught(Ballast) m

(max)119190 270 42.00 21.20 15.60 8.4112900 261 40.20 21.40 15.50 10.62 (Max)113180 261 40.60 24.00 16.00 10.69 ”102824 259 41.30 20.40 14.20 8.29 ”118000 261 42.00 22.80 16.13 9.0 ”104330 259.7 38.00 21.30 15.52 9.37 ”111120 261 40.60 23.00 16.00 9.36 ”98720 255 40.20 23.90 14.63 9.00 ”

113180 261 40.60 23.00 16.00 9.74 ”


550

A.6.1.3 CLASSIFICATION OF CONTAINER VESSEL

ContainerVessel

TEUcapacity

DWT (ave) Lm

Dm

Bm

1st generation 750 - 1100 14,000 180 - 200 9.0 27.02nd generation 1500 - 1800 30,000 225 - 240 11.5 30.03rd generation 2400 - 3000 45,000 270 - 300 12.5 32.04th generation 4000 - 4500 57,000 290 - 310 11.5-12.5 32.3Panamax-plus 4300 - 4600 54,000 270 -300 11 - 12 38 - 40Conbulk mostly Panamax-size bulk

carriers

A.6.1.4 TANKER DIMENSIONS

Ship size (1,000DWT)

Draft (m) Beam (m) Length (m)

20 9 22 18050 12 31 23570 13 35 260100 15 41 270150 16,5 46 300200 19 50 330250 21 52 340300 23 55 350550 28,5 63 415

Berthing Structures


A.6.1.5 DISTRIBUTION OF WORLD FLEET OF TANKERS

Ship size (1000 DWT) Number of ships30 to 80 347

80 to 130 357130 to 180 274180 to 230 49230 to 280 294280 to 330 66330 to 380 25380 to 430 21430 to 480 5480 to 530 4530 to 565 2

A.6.1.6 MOORING EQUIPMENT FOR DIFFERENT SHIP SIZES

Ship size (DWT) Mooring equipment25,000 14 polypropylene dia 60 mm75,000 20 polypropylene dia 72 mm

140,000 20 polypropylene dia 80 mm250,000 24 polypropylene dia 88 mm550,000 20 steel dia 42 mm

+ 2 polypropylene dia 80 mm


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Documents

Berthing Structures