2.0 Design Report

1. Structural Design Concept

1.1 Scope

This calculation sheet applied to the structural design of part of the POWER

HOUSE superstructure for the SONDU/MIRIU HYDROPOWER PROJECT in

Nyanza province in the Republic of KENYA.

1.2 Units of measurement

The units of measurements used in the design were the SI system.

1.3 Design Codes and Standards

1) BS8110 – British Standard for structural use of Concrete

2) BS5950 – British Standard for structural use of steelwork in buildings

3) BS2573 – British Standard for Rules for the design of Cranes (Part I).

4) BS6399 – British Standard for Loading for Buildings (Part I).

5) UBC – Uniform Building Code.

1.4 Properties of structural materials

Concrete

Concrete strength used for all structural members was 25N/mm2 at 28 days.

Reinforcement bars

All reinforcement bars used in the design were in accordance with BS 4461 having

minimum yield strength of 425N/mm2

Structural Steelwork

All structural steelwork used was grade 43 and in accordance with BS 4360.

1

Bolts for structural steel connections were friction grip type in accordance with BS

4395.Anchor bolts used were grade 8.8 in accordance with BS 4190.

Welds for structural steel connections were E43 electrodes in accordance with BS 639.

1.5 Earthquake forces for structures

The static horizontal force due to an earthquake on the structure is given by:

V = Z I C

Where :

V = the total design lateral force at the base

Z = seismic zone factor given in table 16-I of UBC 1994.

I = importance factor given in table 16-K of UBC 1994

C = Numerical coefficient specifed in Section 1628.2.1 of UBC 1994.

RW = Numerical coefficient given in Tables 16-N and 16-P of UBC 1994.

W = the total seismic dead load

1.6 Structural design concept

The powerhouse was designed as a reinforced concrete structure. For the design,the

powerhouse was divided into a superstructure (handled exclusively as a building

structure) and a substructure(treated as specialised civil works structure housing

turbines,generator and related power generation equipment).The design calculations

presnted cover the design of the superstructure only. The foundation is designed asfixed

since the columns are anchored into heavily reinforced civil works structures as least

dimensions of 2500mm x 2500mm and more than three meters deep,braced by very deep

beams (1500 x 1500mm) in all four dimensions.

2

WRW

Analysis of the superstructure

The three dimensional structure was broken down into two dimensional plane frame along

the grid lines in the two orthogonal directions.the plane frame was then analysed using the

computer program STAADIII to determine the design axial loads,shearing forces and

bending moments.

Design of members

Reinforced concerete design of the superstructure such as slabs,corbels,beams and

columns were designed in accordance with the recommendations of BS 8110-1997. The

structural design of steel roof framing system and the crane runway girders was based on

the specifications of BS 5950:Structural Use Of Steelwork In Buildings.

Both these Design Codes are based on the principles of limit state design and therefore the

design loads were multiplied by partial safety factors. The values of these factors varied

depending on the type of loadings or loading combimations under consideration.

Calculation of steel area for beams and slabs

Rectangular beams and slabs

Concrete Force C = 2 (fcu b (0.90) x = 0.4 fcu b x ……….(1)

Steel force T = 0.95 fy Ast ……………(2)

Now Z = d – 0.45 x

3

Fcu = concrete strength

Fy = yield stress of steel

3 1.5

From (1) and (2), Z /d = (1 – 0.95fy Ast / fcu b d) ……………(3)

Taking moment for the tensile force about centre of compression:

M = 0.95 fy Ast Z ……..…….(4)

From (3) and (4) by eliminating the erm Ast,

Z / d = {0.5 + (0.25 – K / 0.9)} where K = M / b d2 fcu

Ratio Z/ d is always be less than 0.95

i.e. Z / d < 0.95

we determine K = M / b d2 fcu and K’ = 0.156

if K > 0.156 then compression reinforcement is required.

Asc = (K – K’) fcu b d 2

As = K’ fcu b d 2 + Asc

Columns

For calculating the reinforcement in columns the charts given in BS8110 Part 3 were used.

4

0.95 fy (d – d’)

0.95 fy Z

2. LOADS

2.1 Loading Patterns

Dead and live loads on the floor slabs were transmitted to the beams in the following

manners. Uniform and concentrated loads were calculated as described below:

2.2 Design loads

The following design loads were considered in the frame analysis for the superstructure:

(a) Dead Loads (DL)

(b) Live Loads (LL)

(c) Crane - Dead Loads only

(d) Crane - Loaded condition

(e) Seismic - (Left & Right)

(f) Wind - (Left & Right)

(g) Monorail Hoist Load

(h) Temperature - (±10 degrees Centigrade)

The above loads were then combined for various loading cases of superstructure to obtain

the worst loading condition as follows:

Case No. Loads combined Ultimate Limit State

1 a + b + c 1.4a + 1.6b + 1.6c

2 a + b + d 1.4a + 1.6b + 1.6d

3 a + b + c + e (to left) 1.4a + 1.6b + 1.4c + 1.4e (to left)

4 a + b + c + e (to right) 1.4a + 1.6b + 1.4c + 1.4e (to right)

5 a + b + c + g 1.4a + 1.6b + 1.4c + 1.6g

5

6 a + b + c ± h 1.0a + 1.0b + 1.0c ± 1.0h

Wind load was not included in the above load cases because the horinzontal seismic shear

is greater than the wind shear and therefore the latter was neglected in the analysis.

2.3 Dynamic and impact load for the crane

(a) For vertical loads, maximum static wheel loads are increased by 25%.

(b) The horizontal force transverse to the rails was 10% of the vertical load.

(c) The horizontal force acting along the rails was 5% of static wheel loads on the rails

2.4 Live Loads

The live loads shown below were the ones used in the analysis of the framed structure

i) Erection Bay (EL.1210.5,designed under Civil Works structures) 50 kN/m2

ii) All other areas as shown below:

Table 1: Live Loads (LL)

Portion Assumed Live Load (KN/m2)

Higher Roof (EL.1224.9)

1.5 (for maintenance of roof ,etc)

Lower Roof (EL.1220.8)

1.5 (for maintenance, A/C,etc)

Floor (EL.1224.9)

10 (Control and communication room)

Balcony (EL.1215.3)

4.0

2.5 Dead Loads (DL)

The dead loads used in the analysis were derived from knowledge of the weights of

various materials used. The calculated values are summarized in tables 2 and 3 as shown

underneath.

6

Table 2: dead Loads (DL)

Portion MaterialThickness

(mm)Weight (KN/m2)

Total Weight (KN/m2)

Assumed Dead Load

(KN/m2)

Roof

(EL.1224.9)

Covering concrete

Levelling concrete t=20mm

3-ply asphalt roofing

Steel plate t = 1.6mm

Concrete slab 150mm thick

80

20

150

1.84

0.46

0.15

0.16

3.6 6.21 6.3

Roof

(EL.1220.8)

Plain concrete t = 80mm

Levelling mortar t = 20mm

3-ply built-up roofing felt

Slab self weight t=200mm

Suspended ceiling

80

20

200

1.84

0.46

0.15

4.8

0.6 7.55 7.6

Floor

(EL.1215.3)

Slab self weight t=200mm

Cement mortar t= 30mm

Vinyl tiles

200

30

4.8

0.69

0.08 5.57 5.60

7

Table 3: dead Loads (DL)

Parapet of Roof Except Roof Slab EL.1220.8

Wall

Crown

Block

Total Area

0.22

0.077

0.056

0.353

Unit 8.500 KN/m

Stair (Above EL.1220.8)Height

Wall

Roof

2.80

150.0 KN

80.0 KN

8

Parapet Of Roof (EL.1224.9) Above EL.1223.0

Wall

Crown

Block

Total Area

0.500

0.077

0.063

0.64

Unit 15.360 KN/m

Balcony (EL.1215.3)

Slab

Finishes

Total

6.72 KN/m2

0.60 KN/m2

7.40 KN/m2

Edge

Handrail

Total

4.08 KN/m

0.50 KN/m

4.60 KN/m

Parapet

Total area

Total Weight

45.0 KN

33.0 m2

275.0 KN

Unit 8.50 KN/m2

2.6 Crane Loads (CDL, COL)

Specification of crane

Design Crane capacity : 1000 KN

Design Crane Capacity : 13 m

Number of Wheels : 8 pieces

Design Wheel span : 4.1 m

2.6.1 Crane Load

Crane dead load W = 750.0KN (including trolley)

Maximum wheel load P = 340.0KN

Minimum wheel load P = 97.5 KN

Average wheel load P = 93.8 KN

9

Parapet on Both Sides of Expansion Joint

Wall

Crown

Block

Total Area

0.132

0.198

0.112

0.442

Unit 10.600 KN/m

2.6.2 Impact Loads

Vertical Loads Pv = 0.25 P

Transverse Horizontal Surge Load PHT = 0.10 P

Longitudinal Horizontal Surge Load PHL = 0.05 P

2.7 Seismic Load (SL) (UBC)

The seismic load was determined using the following formula:

V = Z I C

Where :

Z = 0.15 (Zone 2A)

I = 1.25

RW = 5.0

C = 1.25 S S = 1.0 Site Coefficient (Given in Table 16-J)

T = Ct hn3/4 Ct = 0.0731 hn = 1223-1210.5

= 12.5m

T = 0.49 Sec

C = 1.25 x 1.0 / 0.492/3 = 2.01

V = 0.15 x 1.25 x 2.01 / 5.0 x W

= 0.08 x W , Say 0.10 x W

2.8 Monorail Hoist Load for Draft Tube Gate (HL)

Hoisting Load Hoist Self Weight Rail Self Weight

10

RW

W

T2/3

Long Term 75 kN 10 kN 2 kN/m

Short Term 200 kN 10 kN 2 kN/m

2.9 Temperature Effects (TE)

The concrete structure was subjected to stresses due to temperature changes of +10

degrees and -10 degrees centigrade.

11

3. MAIN FRAME ANALYSIS FOR SP4 (A-D)

3.1 Loading cases considered

In the analysis given below, the forces and moments due to crane loading are determined .

Table 4:Load Condition For Transverse Frame Model 4(A-D)

No. description Crane Position

Crane Operation

Seismic force

Standard Load

1 Dl Dead Load2 LL Live Load3 CDL Crane Dead Load Line A4 CDL Crane Dead Load Line C5 COL Crane Operating Load Line A Moving A-C6 COL Crane Operating Load Line A Moving C-A7 COL Crane Operating Load Line C Moving A-C8 COL Crane Operating Load Line C Moving C-A9 SL Seismic load (DL+LL) ACTING A-D10 SL Seismic load (DL+LL) ACTING D-A11 SLC Seismic Load by Crane Line A ACTING A-D12 SLC Seismic Load by Crane Line A ACTING D-A13 SLC Seismic Load by Crane Line C ACTING A-D14 SLC Seismic Load by Crane Line C ACTING D-A15 TE Temperature Effect(+10 degrees)16 TE Temperature Effect(-10 degrees)17 HL Hoist Load (Long Term)18 HL Hoist Load (Short Term)

Load Combinations21 1.4DL+1.6LL+1.4CDL Line A22 1.4DL+1.6LL+1.4CDL Line C23 1.4DL+1.6LL+1.6COL Line A Moving A-C24 1.4DL+1.6LL+1.6COL Line A Moving C-A25 1.4DL+1.6LL+1.6COL Line C Moving A-C26 1.4DL+1.6LL+1.6COL Line C Moving C-A27 1.4DL+1.6LL+ 1.4CDL +1.4SL+1.4SLC Line A ACTING A-D28 1.4DL+1.6LL+ 1.4CDL +1.4SL+1.4SLC Line A ACTING D-A29 1.4DL+1.6LL+ 1.4CDL +1.4SL+1.4SLC Line C ACTING A-D30 1.4DL+1.6LL+ 1.4CDL +1.4SL+1.4SLC Line C ACTING D-A31 1.4DL+1.6LL+1.6HL(L Term)+1.4CDL Line C32 1.4DL+1.6LL+1.6HL(S Term)+1.4CDL Line C33 1.0DL+1.0LL+1.0CDL+1.0TE Line A34 1.0DL+1.0LL+1.0CDL+1.0TE Line C35 1.0DL+1.0LL+1.0CDL-1.0TE Line A36 1.0DL+1.0LL+1.0CDL-1.0TE Line C

12

Table 5: Live Moment Due To Eccentricity, Frame 4, (A-D)

FromJointNo.

Joint Load(KN)

From Member No.

Uniform Load Triangular Load TotalPy

(KN)

Mz

0.25*Py

(KN-M)

Moment at Joint No.

W(KN/m)

L(m)

W*L(KN)

W(KN/m)

L(m)

W*L/2(KN)

21 18.5322~25 19.11

37.64 37.64 9.41 729 18.53 11 6.68 4.45 14.85

25~28 19.119 10.9410 2.73

51.31 14.85 66.16 16.54 8

Table 6:FRAME 4 , A ~ D DEAD LOAD : MEMBER LOADS:

Level EL +

Load Descriptio

n

Unit Uniform Load Trapezoidal Load

Weight Length Loadh1

(m)w1

(KN/m)d1

(m)h2

(m)w2

(m)d2

(m)Member No.(Kn/m2) b w

(KN/m) (m) (KN/m)

1220.8 RG3 8.64 0 8.64 11 , 12

Roof 7.6 0 0 0 4.45 33.82 2.225 11 , 12

7.6 4.45 33.822.22

5 0 0 4.45 11 , 12

1215.3 1G3 10.08 0 10.08 9 , 10

Floor 8 0 0 0 4.45 35.60 2.225 9 , 10

8 4.45 35.62.22

5 0 0.00 4.45 9 , 10

(A) C1 16.8 0 16.8 4

C1 36 0 36 1

(C) C3 16.8 0 16.8 6 , 8

C3 36 0 36 5

C3 36 0 36 2

(D) C4 11.76 0 11.76 3 , 7

13

HOIST LOADFRAME 4, A ~ D

EL + Load Description

Load Distance Mz Load @ Load

P L P x L Joint Case(KN) (m) (KN-m) No.

1220.8 Hoist, Self weight 10

Lifted Load 75 85 1.7 144.5 11 Long Term

1215.3 Hoist, Self weight 10

Lifted Load 200 210 1.7 357 11 Short Term

14

3.2 Truss Modeling and Loading Conditions

Truss SG-1 is part of the frame model of superstructure at Line 4.

Figure 7.3.4: FRAME SP 4 (A – D)

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1700

2200

5500

4800

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12

22

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24

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25

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3938

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3231

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811 1211 12

910

9

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2

C

2

3

3

11

6

7

44504450

8900

[email protected] = 14500

14500

A D

350

750

750

mailto:[email protected]

THE frame shown above is sampled to show how the analysis was carried out. The sizes of reinforced concrete elements are as shown below:

RC Member B (mm) H (mm)

1 1000 1500

2 1000 1500

3 700 700

4 700 700

5 1000 1500

6 700 1000

7 700 700

8 700 1500

9 600 1000

10 600 1000

11 600 800

12 600 800

Steel Members Size

13 ~ 20 150 x 100 x 10 RHS

21 ~ 28 200 x 100 x 10 RHS

29 ~ 45 100 x 100 x 10 RHS

16

3.2.1 Sp 4 (A – D) For Dead Loads on Frame

Modeling of all Dead Loads (DL) forces acting on the sub-frame SP4 (A-D) is as given

below. The self weight of the steel truss is not given and will automatically be calculated

by the analysis software (STAAD III)

Figure……………….. for deal loads(DL). units : KN,M

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1700

2200

5500

4800

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22

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24

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25

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3938

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3231

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33

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41

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35

26

43

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28

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1917

27

44

8

11 12

9 10

9

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10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-156.58 -79.24 -79.24 -79.24 -79.24 -79.24 -79.24 -79.24 -156.58

-183.62-173.07 -344.79

-9.75

-127.92

-199.04

-237.81

-269.52

-34.27 -34.27

-16.58

-373.88

-11.76

-11.76

-8.64

-10.08

-32.5

-35.6 -35.6 -36.0

-16.8

143.4

-254.02

-16.84

1

1

-36.0

-127.92


3.2.2 SP 4 (A – D) For Live Loads on Frame

Modeling of all Live Loads (LL) forces acting on the sub-frame SP4 (A-D) is as given

below.

Figure……………….. For Live loads (LL). Units: KN, M

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1700

2200

5500

4800

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12

22

13

23

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24

15

25

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26

17

27

18

28

19

29

20

29

13 14

22

3938

21

30

15

40

23

3231

25

42

16

33

24

41

34

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35

26

43

36

20

37

28

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1917

27

44

8

11 12

9 10

9

5

10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-13.17 -18.53 -18.53 -18.53 -18.53 -18.53 -18.53 -18.53 -13.17

-28.55

-14.27

-42.07

-380.6

-30.36

-190.2

-6.68 -6.68

-214.92

-11.76

-89.0 -89.0 19.51

-254.02

4

1

1

7


3.2.3 SP 4 (A – D) for Crane Dead Loads (CDL)

Modeling of Crane Dead Loads (CDL) forces acting on the sub-frame SP4 (A-D) with

maximum loading at Grid A is as given below.

Figure……………….. For Crane Dead Loads (CDL) [A: MAX] Units: KN, M

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1700

2200

5500

4800

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12

22

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24

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25

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26

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27

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3938

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40

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3231

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41

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35

26

43

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37

28

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1917

27

44

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11 12

9 10

9

5

10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-226.8

170.1

-237.8

-317.1

4

1

1

7


SP 4 ( A – D)

Modeling of Crane Dead Loads (CDL) forces acting on the sub-frame SP4 (A-D) with

maximum loading at Grid C is as given below.

Figure……………….. For Crane Dead Loads (CDL) [C: MAX] Units: KN, M

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1700

2200

5500

4800

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12

22

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25

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9 10

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C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-317.1

237.8

-170.1

-226.8

4

1

1

7


3.2.4 SP 4 (A – D): CRANE OPERATING LOAD (COL)

1) [Max A – C]

Modeling of Crane Operating Load (COL) forces acting on the sub-frame SP4 (A-D) with

maximum loading at Grid A and crane travelling from A to C is as given below.

Figure……………….. For Crane Operating Load (COL) [A: MAX:- A-C] Units: KN, M

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1700

2200

5500

4800

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12

22

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23

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25

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26

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3231

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1917

27

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11 12

9 10

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10

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6

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8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-360.1

224.1

-965.3

-1225.8

4

1

1

7

41.8

41.8


2) Crane Operating Load (Col) [Max C – A]


maximum loading at Grid A and crane travelling from C to A is as given below.

Figure……………….. For Crane Operating Load (COL) [A: MAX:- A-C] Units: KN, M

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1700

2200

5500

4800

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9 10

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C

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3

3

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6

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44504450

8900


14500

A D

350

750750

-360.1

-41.8

-41.8

-1225.8

4

1

1

7

-873.4

316.1


3) Crane Operating Load (Col) [Max A – C]


maximum loading at Grid C and crane travelling from A to C is as given below.

Figure……………….. For Crane Operating Load (COL) [C: MAX:- A-C] Units: KN, M

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2200

5500

4800

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3231

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1917

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C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-1225.8

873.4

-316.1

-360.1

4

1

1

7

41.8

41.8


4) Crane Operating Load (Col) [Max C – A]


maximum loading at Grid C and crane travelling from C to A is as given below.

Figure……………….. For Crane Operating Load (COL) [C: MAX:- C - A] Units: KN, M

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1700

2200

5500

4800

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25

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1917

27

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9 10

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2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-1225.8

-41.8

-41.8

-360.1

4

1

1

7

-224.1

965.3


3.2.5 SP 4 (A – D) for Seismic Load Case

Modeling of Seismic Load Case (SL) forces acting on the sub-frame SP4 (A-D) is as

given below. These forces were considered as 10% of Y direction loads of Dead Load,

(DL), Live Load, (LL), and Crane Dead Load (CDL). The calculated seismic load was

applied to the frame in the X- direction.

25

1700

2200

5500

4800

21

12

22

13

23

14

24

15

25

16

26

17

27

18

28

19

29

20

29

13 14

22

3938

21

30

15

40

23

3231

25

42

16

33

24

41

34

18

35

26

43

36

20

37

28

45

1917

27

44

8

11 12

9 10

9

5

10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-226.8

170.1

-237.8

-317.1

4

1

1

7


Figure……………….. For Crane Dead Loads (CDL) [A: MAX] Units: KN, M

26

3.2.6 SP 4 (A – D): For Hoist Loads

1. Long Term Hoist Load

Figure……………….. For

27

1700

2200

5500

4800

21

12

22

13

23

14

24

15

25

16

26

17

27

18

28

19

29

20

29

13 14

22

3938

21

30

15

40

23

3231

25

42

16

33

24

41

34

18

35

26

43

36

20

37

28

45

1917

27

44

8

11 12

9 10

9

5

10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-144.54

1

1

7

-85.0


2. Sp 4 ( a – d): For Short Term Hoist Load

Figure……………….. For

28

1700

2200

5500

4800

21

12

22

13

23

14

24

15

25

16

26

17

27

18

28

19

29

20

29

13 14

22

3938

21

30

15

40

23

3231

25

42

16

33

24

41

34

18

35

26

43

36

20

37

28

45

1917

27

44

8

11 12

9 10

9

5

10

4

6

5

8

2

C

2

3

3

11

6

7

44504450

8900


14500

A D

350

750750

-357.04

1

1

7

-210


4. STRUCTURAL DESIGN OF MAIN FRAME MEMBERS

4.1 Results of Computer Analysis

29

4.2 Structural Design of Main Frame Members

4.2.1 Design of slab 1S1

30

4.2.1 Design of slab 1S1

31

4.2.1 Design of slab RS1

32

Roof truss designs

Loading

The main frame analysis models of the superstructure in section 7.3 of this report include the main truss SG-1. The most critical frame considered for the analysis and design of the truss SG-1 is along the grid line 4,A-D.

There are secondary trusses (SB-1) and (SB-2) built into the main trusses and at right angles to it.

The loading from the secondary trusses were taken as point loads on the main trusses at panel points which are 1900mm c/c

The roof dead load and live load were as follows:

Roof dead load (DL) at EL. 1224.9 : 6.3Kn/m2 (Refer to section 4.1)

Roof Live Load (LL) at EL. 1224.9 : 1.5 KN/m2 (Refer to section 4.2)

Design of Steel Deck Plate

Stress check

Load, w = 6.3 kN/m per meter width

Span, L = 1900mm (Max.)

Assuming simply supported span,

Bending moment, M = wL2 / 8 = 6.3 x 1.9 x 1.9 = 2.84KN-m per metre width 8

Considering dead load acting on steel deck plate

Ultimate moment, Mult = 1.4 x 2.84 = 4.0 KN-m per metre

width

Bending Stress in Plate = Mult / Z = 4.0 x 10 6 = 102 N/mm2 < 265 N/mm2

39.3 x 103

(OK)

33

Deflection check:

σmax. = 5 x w x L 4 = 5 x 6.3 x 1.9 4 384 x E x I 384 x 2.05E-04 x 1.82E+06

= 2.9E-03m = 2.9mm

L/σ = 1900 / 2.9 = 655 > 360 (OK)

Deflection check for truss SG-1:

For the calculations regarding deflection of truss SG-1, reference to be based on the

displacement diagrams…………….and ……… below

i) Determination of max deflection due to Dead Load

σDL = 25.5 – (2.44 + 3.41) = 22.6mm ………(1) 2

ii) Determination of max deflection due to Live Load

σLL = 5.72 – (0.27 + 1.07) = 5.1mm ………(1) 2

iii) Compute maximum total deflection due to combined Dead Load and Live Load

σmax = σDL + σLL

= (22.6 + 5.1) mm

= 27.7 mm

iv) Check on limiting deflection ratio (L / σ)

34

L / σmax = 15200 / 27.7 = 549 > 360 OK

NOTE:

The calculated deflection was based on the assumption that the main truss SG-1 was

simply supported. However it is to be noted that secondary trusses were connected to the

main truss and therefore actual deflection were a lot less than the calculated value of

27.7mm.

35

Documents

2.0 Design Report