Bridge Design

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BUKU PANDUAN REKABENTUK JAMBATAN

Cawangan Jalan, Ibu Pejabat JKR, K.L

FOR INTERNAL USE ONLY

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CONTENTS

.Preface.

Chapter-1STANDARD JKR PRACTICES IN BRIDGE DESIGN

Organisation Objective-Function-Scope of Work. Standard Design

Practices-Design ProcedureBridge Furnishings-Standard Prestressed Beams

Chapter 2 - HYDROLOGY 20,

Factors Affecting Florid Runoff Flood History Rational Method-Unit Hydrograph Method-Regional Flood Frequency Method-Determination ofthe Flood Water Level and velocity-Computation of Back Water Curve-Presentation of Sketch Proposal .

Chapter 3 - BRIDGE LOADING 65

Loads Acting On A Bridge Superstructure-Procedure For Determination Of Loads

Chapter 4 - DECK SLAB 104

Pigeaud's Method-Westergaards Method-Application

Chapter 5 - BEARING, DOWEL BARS, EXPANSION JOINTS 114

Bearing: Functions-Types-Elastomeric BearingsProperties of Elastomer-Basic Assumptionsin Design ' Dowel Bar: Design of Dowel Bar Expansion Joint: Functional Requirements-ClassificationSelection of Joint Type-Design Consideration-Design Load Anchorage System. Installation-Provision for DrainageMaintenance

Chapter 6 - PIER 146

Design Consideration-Pier Components-LoadingPile Layout and Stability-Design of Pier Base and Stem-Detailing

Chapter 7 - ABUTMENT 168

Types of Abutment-Modes of Failure-Scouring Protection and Drainage-Design LoadingsCantilever Type Retaining Wall Abutment Counterfort Retaining wall-Joints in Retaining Wall Abutments-Abutment For The wideningof Bridge.

Chapter 8 - FOUNDATION 322

Part I: Design of Bridge Foundations.323

Shallow Foundations-Piled Foundations-Lateral Load Capacity of.Piles Analysis of Global Pile Group-Unc6rtainities of the Analytical MethodsGood Design Practice _

Part II: Design of Piled Foundation332

Classification-Common Types of Piles Used in JKR Projects-Selection of Pile Type-Design of Single Pile-Factor of Safety-Pile Bearing on Rock-pile Bearing capacity-Negative skin Friction-Design of pile Group

Chapter 9 - DESIGN CODES AND TRAFFIC LOADING FOR HIGHWAYBRIDGES 364 Current and Future Design Standards-Limit state Design-Standard Highway HAAnd HB Loadings-Secondary Highway Loading

Appendices: Philosophy of Limit State DesignDefinitions of Some BridgeTerms-A.storical Development of BS 5400-Terms of Reference for the DesignAnd Supervision of Bridges.


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Chapter 10 - WORKED EXAMPLE OF JAMBATAN DI ATAS SG. ALOR PASIR KELANTAN

Data: Proforma, location plan, cross section of river at bridge site, general layout

i - viHydrological CalculationCalc.Sheet 1 - 10Loadings on Bridge Superstructure 11 - 20Design of Rubber bearing andDowel Bar 21 - 32Design of Deck Slab 33 - 38Pier 39 - 60Abutment 61 - 92EXAMPLE OF WORKING DRAWINGS

APPENDIX 1-8METRIC CONVERSATION TABLE

SEKALUNG BUNGA

'Setinggi*-tinggi terima kasih dan penghargaanhendaklah dirakamkan'bagi mereka yang telahbanyak menyumbang dan berusaha untuk men-jayakan penerbitan Buku Panduan RekabentukJambatan ini:

Sebelum 1984

Ir. Omar bin Ibzafrim.Ir. Kassim JunidIr. Hon Too FangIr. Dzulkifli b. AbdullahIr.-Mariyam bt. IsmailIr. Will'iam Tan Chee KeongIr. Ng See KingIr. Abu Hanifah b. AbdullahIr. Lim Cheng HockIr. Lee Chee HaiIr. Yap Huat HoeIr. Yu Hain Teck

Selepas 1984

Ir. Tham Kum Weng

Ir. Nasaruddin b.Meor Abu BakarIr. Rohani bt. Abd. Razak Ir. Mohd. Murshid b. OmarIr. Dang Anom bt. Md. ZinIr. Wan Abdul Aziz b.Hj. AriffinIr. Baharanuddin b. Che ZainIr. Sabariah bt. BachikIr. Ng See King JIr. Mohd. Hakim b. Mohd. AminIr. Dzulkifli'b. AbdullahIr. Abdul Halim b. MarzukiIr. Abu Bakar b. Mohd. SaidIr. Ku Mohd.Sani b.Ku Mohamad .Ir. Shamlan b. HashimIr. Lim Char ChingIr. Md. Razali b. Hj. YusakIr. Othman b. IbrahimIr. Ahmeed Tarmizi b. RamliIr. Mohd. Hisham b.Mohd. YassinIr. Zainuddin b. JasmaniIr. Shamsuddin b. Sabri.Ir. Mustaffa Kamal b. Abu BakarIr. Mohd. Zamri b. ShaariIr. Sohaimi b. Mohd. YassinIr. Abd. Latif b. Mokhtar Ir. Tengku Hishamuddin b.Tengku Abdullah.

Penyediaan Pelan-pelan

Puan Salmah bt. WahabEncik Kamaruzamau b. Osman.Encik Abdul Aziz b. SabdaEncik A. Kamal b. A. RahimEncik Arshad MarzuniEncik Abd. Hadi b. Mohd. SharifEncik Johari b. YahyaEncik Mohd. Nor b. ZainuddinEncik Ghazali b. JantanPuan Siti Hafsah bt.KusniPuan Hayati bt. Mohd. NayanPuan Ooi Kooi KeeEncik Zainal Akmar b. YaacobPuan Salasiah bt. OthmanPuan Yeo Seok KinEncik Zailan b. JumaniEncik Teoh Jit LiangEncik Omar b. Munam


Page 4Cawangan Jalan, Ibu Pejabat JKR, K.L

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Jurutaip

Puan Normah bt. Md. NoorPuan Ruhani bt. Hamat Puan Sally Wong

Kakitangan-kakitangan Lain Yang Turut SamaMenjayakan Penyediaan Buku Panduan ini.

Puan Rodiah bt.'Mat SamanEncik Abd.Hazim b. IbrahimEncik Mohd. Aziz b. ShamsuddinEncik Onn b. SulaimanEncik Tajuddin b. HamzahCik Endon bt.MansorEncik Rosli b. TalibEncik Mat Yusof b. HashimPuan Jaswir KaurPuan Shaharah bt. M. ShariffEncik Ishaik b. IndonPuan Hawa bt. Mohd. Said Encik Md. Shamri b. Hj. Amin.

C H A P T E R 1

STANDARD JKR PRACTICES INBRIDGE DESIGN

1. INTRODUCTION

1.l Organisation Objective

To plan and improve the development of the infrastructure and public services in the transportation system such as bridges, flyovers & culverts for roads so that they will be safe, of high quality and economical so as to fulfill the country's social and economic development.

1.2 Function1. To plan and design new structures or

suggest remedial works for existingstructures of river,bridges/flyovers/ foot bridges/culverts for federal, state and regional scheme roads.

2. To co-ordinate the design activities of bridge projects for federal roads designed by the Consulting Engineers.

3. To plan and implement projects of major bridges for federal roads.

4. To give technical advice to the JKR States/Projects/ Road brcmcK in the structural design of bridges, bridge construction activities and on the transportation of heavy vehicles on JKR bridges.

5. To plan and implement research program to improve the design construction and maintenance bridge in JKR.

6. To participate in training activities by giving lectures and talks in courses organised by the JKR Training Centre and other units/sections.

1.3 Scope of Work .

The design works in the Bridge Section involve the preparation of designcalculations, presentation ahd checking of working drawings, preparation of specification and bill of quantities. The time taken to fully complete a project will depend on the availability of the necessary imformation, plans, etc. forwarded to this section. The procedure in carrying out A. design project is shown in the flow chart ofthe Bridge . Design Section (Appendix I).

2. Standard Design Practices:

2.1 Types of Bridges

The types of bridges designed by the Section are road bridges over highways, railway line, river and sometimes pedestrian bridges. All bridges designed are of reinforced and prestressed concrete based on the length of the standard beams available in the Section. See (Appendix II) Attempts arenow underway to.design continuous boxgirder bridges.


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2.2 Design Codes

The design of concrete bridges in the section has been based on British Standards such as the BS 153 Part 3A(loading), CP '114 (reinforced concrete) and CP 115 (prestressed concrete). In addition, technical memoranda published by the British Department of Transport are also used. These memoranda. are essential reference material because firstly, they lay down principles of design for bridges based on their distinct features as compared to other structures and secondly, they keep abreast of current design recommendation based on research.

The code of practice on Limit State Design (CP 110) is not applicable to design of bridges because it is not compatible to the loading requirements of BS 153 Part 3A. A new bridge design code incorporating the Limit State Design and various technical memoranda embodied in BS 5400 has been available since 1978. However, controversial parts of the code are still under review in Britain and not yet implemented in full.

A list of design codes related to the design of bridges as practised by this section is shown in Appendix III. 11 It is a practice in the section that all road bridges are designed to HA loading and checked for 45 units of HB loading guided along the centre line of the carriageway. The procedure ofcomputing the designed live loads and dead loads is dealt with in the chapter on loading. For a skew angle of less than 200, the beams can be used and if the skew angle is greater than 200, the beams should be analysed using the GRIDP/STRU analysis computer programme that is available in thecomputer section.

3. Design Procedure:

3.1 Proforma

With reference to the flow chart in the implementation of the bridge designs, the proforma is very important to the designer to decide the arrangement of the bridge for the preparation of a sketch proposal .When there is a requestto design a bridge from other sections, the proforma form will be sent to the particular section to fill in their requirements e.g. location, t9pe of road, services and longitudinal cross section of the river at a distance of 100 ft. upstream and 100 ft. downstream if it is over a river. Roads are classified by theirJKR standard types (Appendix IV)

The selection of the type of parapet for abridge is of fundamental importance to its appearance.It is a practice in the

section, to have either a solid concrete parapet or a steel railing (Appendix VI). Each can have visual merits depending on the general configuration of the bridge structure. In the case of a bridge over a highway, it would be appropriate to have.a steel railing so that the bridge deck will appear slender. For remote areas, since maintenance is difficult, the use of concrete parapet is preferable.

4.2 Services

The service that are usually required by the client.to be placed on the bridge structure are watermains, telephone and electrical ducts. Brackets for the watermain are provided in the form of 'J' or 'L'shape as in Appendix VI. The telephone and electrical ducts are usually placed inthe concrete kerb and if there are more ducts, they are hung by the side of the beam.


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5. Standard Prestressed Beams

As mentioned earlier the arrangements of the bridge are based on the available standard pretressed beams as shown in Appendix II. These comprise of post-tensioned I beams and pre-tensioned inverted T beams. The choice between these two types of prestressed beams depends on the span and locality of the project. Pre-tensioned beams have the advantage of being cast in the factory under good quality control. But they canonly be in short length probably not more than 20 m because of the difficulty in transporting them to the work site.

Post-tensioned I-beams can span greater lengths and are best used when the bridge site is not easily accessible or remote. Casting and prestressing on site will solve the problem of transportation of the finished beams.

6. References

Apart from the design codes mentioned earlier, the following are popular references used in the section:

1. Concrete Bridge Design - R.E. Rowe.2. Introduction to Structural Design

(Concrete Bridges - Derrick Beckett.3. C & CA/CIREA

Recommendation on the use of inverted T-Beams and pseudo-box construction - Wilson & Manton.

4. The Analysis''of Right Bridge Deckssubject to Abnormal Loading - Morrice & Little.

5. Design of Prestressed Concrete Structure -T.Y. Lin.

6. Standard Bridge Beams for spans from 7m-to 36m - Sommerville. 7. Foundation & Pile Design - Tomlinson.

PETUNJUK:

PPK - Penolong Pengarah Kanan

K - Kerani

JKK - Jurutera Kerja Kanan

PB - Perekabentuk

Py - Penyemak

KP - Ketua Pelukis

PL - Pelukis

OK - Operator Kamera

JT - Jurutaip

Pel.Pej. - Pelayan Pejabat

P/TP - Pengarah/Timbalan Pengarah

J/PP - Juruteknik/Pelukis Pelan


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PPK

K

JKK

PB

PB

PY

PB

PY

PPK

MULA

KP

PL

KP

PB

Terima permohonan, buat keputusan untuk direkabentuk olehUnit Jambatan

Buka fail, kandungkan surat

Kaji dan lantik perekabentuk dan penyemak

Kumpul maklumat struktur melintasi sungai

Minta ‘bridge proforma’ Buat perkiraan haiderologi

Semak Perkiraan haiderologi

Rangka Pelan Cadangan

Semak Pelan Cadangan

Luluskan Pelan Cadangan?

Lantik Pelukis

Lukis Pelan Cadangan

Semak dan tandatangan pelan cadangan

Semak dan tandatangan pelan cadangan

YaTidak

Tidak Ya

A. CARTA ALIRAN KERJA REKABENTUK PERMULAANSTRUKTUR JAMBATAN

APPENDIX 1 A

* Bersambung dimuka surat sebelah

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CARTA ALIRAN KERJA REKABENTUK PERMULAANSTRUKTUR JAMBATAN

APPENDIX 1 A

PPK

OK

PB

JT

PB

PPK

K

Pel. Pej.

TAMAT

* Sambungan dimuka surat sebelah

TidakYa

Luluskan Pelan Cadangan?

Buat salinan pelan cadangan

Tulis surat

Taip Surat

Semak dan tandatangan ringkas

Tandatangan surat

Semak dan failkan surat / lukisan

Hantar surat / lukisan

Proses kerja rekabentuk terperinci struktur baru

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PB

PY

JKK

KP

PL

KP

MULA

PB

PY

JKK

P/JP

Cadangkan konsep struktur / rekabentuk piawai

Luluskan ?

Siapkan rekabentuk terperinci

Semak perkiraan

Luluskan?

Atur kerja dan lantik pelukis

Siapkan lukisan terperinci

Semak dan luluskan

Semak dan tandatangani


Luluskan

Tandatangani Lukisan

Serah pada O.K

YaTidak

Ya

B. CARTA ALIRAN KERJA REKABENTUK TERPERINCI BARU UNIT JAMBATAN

APPENDIX 1 B


Terima ulasan dan kelulusan cadangan

PPK

PPK/JKK

O.K

TAMAT

Dari Proses Kerja Rekabentuk Permulaan


Buat Salinan

Proses Kerja Penyediaan Dokumen Meja Tawaran

JKK/PPK

PB

PPK/JKK

Tidak Ya

Tidak

Ya

Tidak

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KP

J/PP

KP

PB

PPK

MULA

JT

PB

Deraf/pinda penentuan dan jadual bahan

Luluskan format penentuan dan jadual bahan ?

Arah bagi kerja

Buat ‘taking off’, abstracting dan billing’

Semak ‘taking off’, abstracting dan billing’

Semak dokumen meja tawaran

Semak dokumen meja tawaran

Luluskan?

Taip dokumen

Luluskan

Ya

C. CARTA ALIRAN KERJA PENYEDIAAN DOKUMEN MEJA TAWARAN UNIT JAMBATAN

APPENDIX 1 C


Terima salinan lukisan

JKK

Dari Proses Kerja Rekabentuk Terperinci

Semak

JKK/PPK

PB

JKK

Tidak Ya

Tidak

YaTidak

PY

JKK

Susun dokumen meja tawaran

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PPK

TAMAT

K

Pel.Pej

Tulis surat

Tulis surat

Semak surat dan tandatangan ringkas

Tandatangan surat

Failkan surat

Susun semula data rekabentuk dan jilid dokumen untuk rekod

C. CARTA ALIRAN KERJA PENYEDIAAN DOKUMEN MEJA TAWARAN UNIT JAMBATAN

APPENDIX 1 C

* Sambungan dari muka surat sebelah

PB

Tidak

Ya

JT

Hantar surat/dokumen

PB

Pb/kp

BUKU PANDUAN REKABENTUK JAMBATANFOR INTERNAL USE ONLY

NO. NO.BEAM OVERALLLENGTH-(m)

EFFECTIVELENGTH-(m)

1.

2.

3.

4.

5.

6.

I-BEAM

1 - BEAM

INVERTED T

INVERTED T

INVERTED T

INVERTED T

31.24

25.00

18.90

16.76

12.50

9.45

30.33

24.23

18.59

16.53

12.34

9:29

STANDARD PRESTRESSED BEAMS AVAILABLE IN THE BRIDGE UNIT

LIST Of RELEVENT B.S CODES & B.E TECHNICAL MEMO FOR BRIDGE DESIGN:

B.S B. E

1. LOADING B.S 153 : Pt3A ' 1972. 1/77.

2. R.C DESIGN CP 114 1/73

3. P.C DESIGN C P 115 " 2/73

4. PRECAST BEAM C P 116 -

5. COMPOSITE CONSTRUCTION CP 117: Pt 11

6. FOUNDATIONS C P 2004 -

7,, ILASTOMETRIC BEARING - 1/76 r

8. NEW BRIDGE CODE B .S 5400 -

9. EARTH RETAINING STRUCTURE - 3/78

10. PARAPET - 5

11. DESIGN CRITERIA FORFOOTBRIDGES - 1/78

12: EXPANSION JOIKTS - 3/72

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LIST OF 0. I.0 HYDROLOGICAL PRO-CEDURES FOR HYDROLOGICALCALCULATION:-

1. HP 1 - ESTIMATION OF THE DESIGN STORM

2. HP 5 - RATIONAL Mtd.

3. HP 11 - UNIT HYDROGRAPH Mtd.

4. URBAN DRAINAGE DESIGN Stds AND PROCEDURES FOR PENINSULAR MALAYSIA

5. HP 4 - REGIONAL FLOOD FREQUEN CY Mtd.

PROFORMA FOR BRIDGE DESIGN

Federal:.................... State:.................... BridgeNo: ................ S7ungai: ..........*........State:.,................... Route orRoad:............................ at. Milestone:................

1. STREAM:(a) FLOOD LEVEL

Normal R.L. ........................Exceptional R.L.................... . Date:..................

(b) NORMAL WATER LEVEL- R.L............... ...........

(c) POSSIBILITY OF DEBRIS DURING FLOODS:........................................

(d) NORMAL VELOCITY .......................h/Sec . ................ .......

2. PLANS FORWARDED:(a) Site Plan ........................... Drg.

No:.............................(b) Longitudinal Section on:

(i) Centre line of Bridge(ii)' 15 m. on either side of centre line of

bridge to a distance of 150 m. on either bank of stream.Drg. No. ..........................

(c) Cross-section through road embankmentnear abutments. Drg. No....................................(d) Plan Showing:

(i) Stream course for 100 m. on either side of bridge

(ii) road approaches within 100 m. of bot ends of bridge. Drg. Not ..........................

(e) Plan showing details of existing piers and abutments and other obstructions, Drg. No:.......................

3 BRIDGE:Proposed deck level. R.L.....................Foot paths:Carriageway: clear distance between kerbs.

4. CONSTRUCTION:State whether:(a) Divided deck type is required:.............................. or (b) Alternative arrangemcnt will be made for traffic di viation during construc-tion:.....................................................................................................

5.. SERVICES:Accommodation required for:(a) water mains. Size:........................(b) Electricity cab1c ducts. Size:......................................... (c) Telephone ducts.Size:.......................................... (d) Lighting standards:..................................

6. GROUND CONDITIONS:(Preliminary information, if available)Whether (a) Open type foundations feasible ............... (b)Good bearing strata. likely atR.L......................... ........ (c) Extremely poor ground ............................ (d)Mackintosh probes details 1n Drg. No:..................... .........

7.STIPULATIONS BY OTHER AliiHGR'.kIES I IF ANY:................................................................................. ............................................... ........................................................


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NOTES ON HYDROLOGICAL CALCU-LATIONS FOW- BRIDGE DESIGN

1. INTRODUCTION

In the design of a hydraulic structure, hydrolog-ical calculation is necessary to determine therate of flow or discharge that the hydraulicstructure will be required to accomodate.

The design discharge is a 'hydraulic load' anal-ogous to the structural load in a structuraldesign.

In a bridge design, we need to determine thedesign flood discharge for a certain ReturnPeriod so we can propose a bridge with thedeck level well above the flood level.

Besides this, we have to calculate the floodvelocity to determine if the river bed is suscep-tible to scouring.

2. FACTORS AFFECTING FLOOD RUNOFF

2.1 SIZE

The size of a catchment area has an importantbearing on the response of the catchment torainfall, and consequently on the methods usedto predict flood runoff.

Topographic maps are valuable aids in obtain-ing the size of -cafchrnent areas.

In the Rational method (HP No.5) the size ofcatchment area is limited to 0.5 - 40 sq. miles.Return Period is the average interval of time (inyears) between the years that contain an event,greater than or equal to the one under consider-ation. It is a statistical measure of the probabili-ty of occurence of a.flood under consideration.

2.2 SLOPE

Many investigations have found that next tocatchment area size, some index representingthe slope of the catchment area is a very

important catchment area characteristic in .comparing f18od magnitudes.

Main channel slope can be determined by sim-ple measurement from topographic maps. Fornon-uniform slope, 'weighted mean slope' canbe used though it can be argued that in thepreparation of H.P. No. 5 the 'rough' slope hadbeen used~so it would be more appropriate touse the 'rough' slope in the calculation.

2.3 LAND USE

The effect of urbanization and land develop-ment on peak flow depend upon the percent ofthe area made impervious and the changesmade in the drainage pattern through the instal-lation of storm sewers and modification of sur-face channels:

DID HP No.5 has recommended as a generalguide, factors to allow for varying amounts ofchange from undeveloped vegetation to agri-cultural crop. (Table 3)

2.4 SOIL TYPE & SURFACE INFILTRATION

The type of soil and its surface infiltrationcapacity affect the amount of runoff in thecatchment area. These factors are taken intoconsideration by the Runoff Coefficient (C).

2.5 STORAGE

Storage within a catchment area may be deten-tion storage, which is the rainfall lost in fillingsmall depressions in the ground surface; stor-age in transit in overland channel flow, or storage in ponds, lakes or swamps. Storagemay also occur in flood control structures likereservoirs.

The effect of storage on peak flows can bequite large. However, this effect has not beentaken into account in DID HP. No. 5, such thatcatchment areas where storage effectis expected to be serve as in the case of reser-voirs, DID HP No.5 should not be used.


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Helpful data can then be obtained from thecontrolling public agencies.

For urban drainage modified rational methodcan be usedin which storage coefficient.(Cs) shall be multi-plied by basic Rational Method formula

Q = CSCiAWhere Cs = 2 tc

__________ 2tc + td

and tc is the time of concentrationtd is the time of flow in the drain but, C is thecomposite runoff coefficient and shall be deter-mined as follows

C = A1 C1 + A2 C2......An Cn_______________________

' AAl, A2 etc. are n areas, each of relatively uni-form land use or Furface character, comprisingthe total area A.And C1, C2 etc. are the corresponding runoffcoefficients obtained from table below.

2.6 RAINFALL

The total amount of rainfall is most importantin producing peak flows from large areas,while the intensity of rainfall is . most impor-tant in producing peak flows from small areas.

Catchment area characteristics and antecedentconditions have a major effect on the propor-tion of rainfall which becomes runoff.

3. BLOOD HISTORY

HISTORICAL FLOODS

The history of past floods and their effect onexisting structures are useful in making floodhazard evaluation studies, including neededinformation for sizing our structures.

Records of the past floods that are useful to a

designer are:(a) Photographs of structures during flood(b) Maximum flood level(c) Distribution of flow and approximate

velocities in different sections of the stream

(d) Duration of flood (e) Magnitude of flood (f) Scour, erosion & sediment deposits(g) Damage to structures & adjacent

property

These information may be obtained from thelocal residents and.the related local publicagencies like the D.I.D.

4. STATISTICAL METHODS IN THE ESTIMATION OF FLOOD MAGNITUDES

Where actual records of runoff from historicalfloods extending over long periods are avail-able, such records may be analysed to furnishthe basic design data.

Unfortunately, in the majority of cases ade-quate runoff records are not available and esti-mated of storm runoff by statistical method hasto be used.

3 methods have been established by the DID,Malaysia:

(a) Rational Method (Hp No.5)(b) Unit Hydrograph Method (Hp No.11)(c) Regional Flood Frequency Method (Hp

No.4)


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5. RATIONAL METHOD (HP No. 5)

5.1 ASSUMPTIONS

5.1.1 Homogeniety of rainfall in terms of time and space

5.1.2 The maximum rate of runoff for aparticular rainfall intensity occurs if theduration of rainfall is equal to or greater than Tc:

*'Tc = Time of concentration is defined as being the time taken for the most remotepart of the catchment to contribute to flow at the design point.N.B. Minimum Tc recommended in HPNo. 5 is 30 minutes.

5.1.3 The maximum rate of runoff from a specific rainfall intensity whoseduration is equal to or greater than TCis directly proportional to the rainfall intensity.

5.1.4 The frequency of occurence of the peak discharge is the same as that of the sample intensity from which it was calculated.

5.1.5 The coefficient of runoff C remains constant for all storms on a given watershed. (Catchment area)

5.2 ANALYSIS OF POINT RAINFALL

Point rainfall is the rainfall records taken at asingle gauging station.

The DID Malaysia had collected rainfallrecords for the peninsular and produced iso-pleths after statistical analysis

These isopleths can be made use of to calculatethe storm intensity for various return periodand duration.


Land Use Runoff Coefficient

Business:-City Areas Fully built-up and shophouses

Industrial:-Fully built-up

Residential:-4 houses/acre4-8 houses/acre8-12 houses/acre12 houses/acrePavementParks (normally flat in Urban Areas)RubberJungle (normally steep in urban areas)Mining LandBare Earth

0.90

0.80

0.550.650.750.850.950.300.450.350.100.75

Table 1 Rational Method Runoff Coefficients for urban centres

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It is customary in engineering practice toassume that, point . rainfall values are applica-ble to areas up to 1sq mile and for larger areasreduced values are to be used (Areal ReductionFactor - Table 2).

5.3 PROCEDURE

5.3.1 INFORMATION

(a) Cross-sectional drawings and other site plans

(b) Topographic maps(c) Design Profoma:

(i) History Flood(ii) Channel characteristic(iii) Client's requirements

(d) DID Hydrological procedures (Hp No. 1 & Hp No. 5)

5.3.2 HYDROLOGICAL CALCULATION

5.3.2.1 Estimation of the design rainstorm (use of Hp.. N0.1)

(a) Adopt Return Period T = 100 years

(b) Determine Time of Concentration

TC = 0.434 A0.117L____________

S 0.467

NBNote that A is in sq. miles

L is in milesS is weighted .mean slope (in percent)

(c) Obtain values of X(T,t) from figs1-8 for T = 2, 20; and t to envelope value of TC. (i.e. t 1, <tC < t2)

(d) Plot values in graph fig.9(fig 10 of Hp No. 1)

(e) Draw straight lines between points representing the same duration.

(f) Read off values of:X(10, ½ ) )X(10,2 ) ) if Tc is between X(100, ½) ) ½ hr. & 2 hrs.X(100,2 ) )

X(10,2 ) )X(10,24 )) if T c is between

2 hrs. & 24 hrs.. X(100,2 ) )

X(100,24 ) )

AND SO FORTH............

(g) Plot the above values in graphFig. 10 (Fig. 9 of Hp. No.1)

(h) Read off values of X(2, TC ) X(10, TC)X (20, TC )X(100, TC )

(i) Compute confidence Limit D = X(20) - X(2)Limit = 0.43 D

(j) Max X(100) = X(100) + 0.43D

* T can be calculated from Hp. No. 8 but it isthe JKR practice to adopt T = 100 years.

5.3.2.2 Flood Estimation

Use of HP No. 5(a) obtain values of X(10) & Max

X(100) (b) Compute 110 = X(10)

______ TC

and reduce the intensity accordingly by the appropriate Areal Reduction FactorTable 2 - (Table 8 of Hp No.1) (c) Evaluate C from fig. 11 &.,12 (d) Compute i100 = X(100)

_______TC

- again applying the appropriate Areal Reduction Factor


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(e) Compute Peak dischargeQ100 - F (C x i 100 x Ac),value of F from table 3 being Land-use Factor. Note that Ac in Acres (1 sq mile = 640 acres)

5.4 RELIABILITY OF THE RATIONALMETHOD

5.4.1 It cannot be over. emphasised to state that the results obtained from the Rational Method should not be adopted indiscriminately because of the following uncertainties in the method:

1. There is a degree of uncertainty Jinvolved in the initial computation of the qT & iTfrequency distributions in the preparation of fig. 12 for values of Runoff coefficient (C)

2. In developing the components of the procedure, the TG relationship and the selection chart for C, averaging is carried out in semi quantitative fashion only.

Lastly, it must be emphasised again that the use of any flood estimation procedures must be complemented by sound engineering judgement and experience. Flood information collected from the local residents in the vicinity can be very useful.

5.4.2 CONFIDENCE LIMITS

The computed value of an event for a certainreturn period by Hp. No.1 is not the 'real' value, and has a certain statistical uncertaintyattached to it.

The standard error can be computed based on the work by Robertson: This standard error can be used to construct two control curves such that 2/3 of the estimate would be expected to fall within this range.

D = X(20) - x(2)Standard error = 0.43D based on 20 years record and return period of 100 years.


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TABLE 2: AREAL REDUCTION FACTOR FA(FROM TABLE 8 OF HP 1)

CATCHMENTAREA Ac(sq miles)

STORM DURATION t (hrs)

1/2 1 3 6 24

0 1.0 1.0 1.0 1.0 1.0

50 0.69 0.80 0.90 0.93 0.95

100 0.61 0.72 0.84 0.89 0.93

150 0.58 0.68 0.82 0.86 0.92

200 0.67 0.80 0.84 0.92

250 0.66 0.80 0.84 0.92

300 0.65 0.80 0.84 0.92

350 0.80 0.84 0.92

400 0.80 0.83 0.92

TABLE 3: LANDUSE FACTOR F(FROM TABLE 2 OF HP 5)

DEVELOPMENT TO AGRICULTUREFROM JUNGLE IN PERCENT

F

0-25 1.00

25-50 1.05

50-75 1.15

75-100 1.20

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6. UNIT HYDROGRAPH METHOD (HP. No. 11)

This method estimate total flood hydrograph for ungauged rural. catchments: This procedure is not applicable to urban catchments. one advantage of this method is that it can be used to distribute runoff from storms of varying temporal pattern. The disadvantage is that.it is fairly tedious to apply.

6.1 REQUIREMENTS

1. It should estimates:(i) The peak flow(ii) The volume and time distribution of

runoff for various recurrenceintervals.

2. Account for significant differences in the catchment characteristics that effect floods.

3. Utilize catchment data that can bereadily determined from topographical maps.

4. Should be simple and relatively fast to apply.

6.2 PROCEDURE

1. Determine the catchment group (From table 4)

2. Compute:(i) L - Length of stream from the out

let to the catchment boundary (mile)it

(ii) Lc - Length of stream from outlet tothe. catchment centroid (See fig. 13)

(iii) A - catchment area(iv) S - Stream slope (Formula is as in

egn.(1)3. Calculate catchment lag, Lg is the time

from half the duration of rainfall excess to half the volume of direct runoff.

Lg=- Ct x [ LLS] n . . . . . . (2) .---------

S

4. Calculate design storm using HP. 1 (Pin)XT tN.B. }for 3 hrs. storm } T is any design

returnPin = XT 3 } period say 50 orfor 4 hrs. storm } 100 yrs.Pin = X T,4 }

5. Calculate direct runoff volume, Q (i) Design storm < 3 ins.

Q = 0.33 P ins. (ii) Design storm > 3 ins.

= P2 ins. --------- (P+6)

6. Calculate Peak Discharge,.gp = Dp x A 640 x Q

----------------------- ft 3 /Sec.(Lg + D/2)

Where Dp = peak ordinate of thedimensionless hydrograph i.e. charateristics of the catchment - (table 5)D = Duration of storm

7. Add baseflow component of 5 cusecs per sq. mile. Table 4: Values Ct and n For Equation


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Table 4: Values Ct and n for Equation

Catchment Type Ct n

Group 1

Group 2

Group 3

Whole catchment very steep andcovered in virgin jungle

Upper catchment very steep andjungle covered, lower catchmentreaches hilly and covered pre-dominantly with rubber

Whole carchment undulating withvariable vegetation including jun-gle, rubber and agricultural devel-opment

2.0

4.0

8.0

0.35

0.35

0.35

Table 5 : Values of Dp, Tb and Tp

Catchment Type Dp Tb Tp Tp/Tb

Group 1 1.06 1.89 C 0.94C * 0.50 *

Group 2 0.89 2.24 C 0.87C 0.39

Group 3 0.75 2.67 C 0.58C. 0.22

* Adapted for design flood estimation

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7. Regional Flood Frequency Method (Hp No.4)

A total of 11 regions (F1 to F11) have been defined in Peninsular Malaysia, within which reasonably consistent regional flood frequency relationship have been established. Thes regions are shown on plate 1, together with locationof the gauging stations used in analysis. location of the gauging stations used in

It has not been possible to provide rational flood frequency coverage for the whole of Peninsular Malaysia. This is especially so for the areas between thecoastline and the foothills of the central and western mountain range. On such areas data in respects of flood peaks are very difficult to obtain because of large flood plain storage and tidal effects.

7.1 Use of Procedure

This procedure may be used for estimating the flood frequency distribution within any of the regions shown on Plate 1. There are two situations, for which different methodsare used-to make the flood estimate:Case 1 : Stations with sufficient data to

define the mean annual floodCase 2 : Stations with zero or very little

streamflow data. '

Example of Case 1

Station No. 4442 Station Name : Sg. Langatat KajangCatchment Area : 148 sq. miles (from Plate1) Flood frequency Region: F4Mean Annual flood: 4503 cusecs (FromAppendix A)From Figure 14, using the region F4 flood fre-quency line,prepare Table 6 shown on page 47.

Example of Case 2

Station: Unnamed point on Sg. Seminyih FloodFrequency Region: F4 (from Plate 1)Catchment area: 148 sq. miles (NB. same asfor 4442) .Mean annual flood (from Figure 16): 3600cusecsFrom Figure 14, using the region F4 flood fre-quency line, prepare Table 7 shown below:

Example of Case 3 (67% confidence limit)Take the same station as for case 1 'Q20 = 6260 )Q2 = 4360 ) From Fig.18R = 1900 )

R = 1900 = 425 Vn f 20

Standard error of the estimate of

Q2 = 0.54 x 425 = 230Q5 = 0.86 x 425 = 366Q10 = 1.23 x 425 = 522Q20 = 1.73 x 425 = 736Q25 = 0.43 x 1900 = 820Q50 = 0.43 x 1900 = 820

Control curves are plotted on the estimatedflood frequency curve for case 1 shown onFig.18. The control curves indicate that two-thirds of the (say) Q25 estimate made fromdata samples of length 20 yrs. would lie in therange 6439 t 820,cusecs, i.e. from 5619 to 7259cusecs.

7.3 Limitation

1. This procedure applies only to the catchmentareas indicated by the position of the meanannual flood - catchment area lines on figures15, 16, 17 and reproduced in Table 8 below:


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Table 6: Reconstituded flood frequency estimates (Region F4, Case 1)

T (yrs) QT/Q2.33 QT(Cusecs)

2.33 1.00 4503

5 1.16 5223

10 1.27 5719

25 1.43 6439

50 1.54 6934

100 1.64 7385

The Flood frequency curve reconstituted for stationNo. 4442 using the data from Table 6 is shownon Figure 18.

Table 7: Reconstituded flood frequency estimates (Region F4, Case 2)

T (yrs) QT/Q2.33 QT(Cusecs)2.33 1.00 4503

5 1.16 522310 1.27 571925 1.43 643950 1.54 6934

The Flood frequency curve reconstituted for the unnamedlocation on Sg. Semenyih using the data from Table 7 is shownon Figure 18.

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Table 8: Range of Catchment Area applicability for each region

Flood Frequency Range of Catchment Area for which

Region procedure is suitable (sq. mile)

F1 30 - 1500 F2 30 - 300 F3 100 - 450 F4 45 - 600 F5 30 - 200 F6 45 - 1200 F7 80 - 400 F8 20 -1000 F9 40 - 2000 F10 40 - 3000

F11 2000-- 10,000

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8 DETERMINATION OF THE FLOOD WATER LEVELFLOOD WATER LEVEL AND VELOCITY

8.1. Manning's Formula:

8.1.1 Manning's Formula is used to calculate the flood Velocity of themain streamv = 1.49 (R) 2/3 (S o)1/2

n8.1.2 The formula is strictly valid for

cross-sections shaped like widerectangles having approximately level bottoms

8.1.3 The hydraulic gradient is assumedto run parallel to the energy gradient(i.e. uniform flow)

8.2. Procedures1. Draw out the cross-section of river

at bridge site to scale on a graph paper.

2. Assume a flood level based on the past flood records (from Proforma)

3. Subdivide the cross-section according to marked changes inroughness.

4. Assign values of Mannings Roughness coefficienct to each'sub section (Table 9)."

5. Further divide the subsections according to marked changes in depth of flow and work out the areas (A) and wetted perimeter (P) for each sebsection Work out the Hydraulic radiifor each subsection:

R i = Ai--------

Pii = no of subsections.

6. Compute the velocity of each subsection by Manning's Formula.


APPENDIX ARegion F4

MEAN ANNUAL FLO O D DATA MAXIMUM RECO RDED FLO O D DATA

Maximum discharge data

STATIO N PERIO D O F Station Regional Date Gauge Height cusecs cusecs Regional Ratio toNO RECO RD Q .33(cusecs) Q .33(cusecs) (ft.above m.s.t) per Return Regional

sq.ml Period (yrs) Q 50

3413 1947-1970 3650 2900 24.4.54 128.3 3950 31.8 41 0.984411 1949-1970 8110 6800 30.10.55 67.8 10800 25.6 80 1.054412 1947-1970 2130 2010 4.6.66 134.7 2530 35.1 10 0.834421 1950-1970 8820 8250 1.11.55 26.8 10900 19.5 14 0.874422 1961-1970 4000 2900 26.11.67 118.5 5000 40.3 >100 1.134431 1948-1970 4000 5010 27.10.57 33.6 5600 20.4 4 0.744432 1948-1970 5220 3920 28.4.52 93.5 7450 39.4 >100 1.254433 1948-1970 1180 1500 14.9.64 103.2 1600 34 3 0.74434 1948-1970 1460 1700 2.2.51 107.8 1680 30 2 0.654441 1949-1970 4800 7450 11.6.54 27.2 6915 14.5 2 0.614442 1948-1970 4500 3350 27.10.57 89.5 7500 50.7 >100 1.474443 2170 2175 4.3.64 109.8 3190 38.9 36 0.97

(FROM APPENDIX B HP" 4)

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Maximum Permissible velocity or nonerrodible velocity is the greatest mean velocity that will not cause erosion of the channel body (Table 7).Vm is not to exceed this velocity.

The discharge capacity should be able to accomodate the peak discharge Q100.If Qc < . Q100Repeat steps 2-8 by a ew trial flood level until Qc is slightly higher thanQ 100 ,

* If the mean velocity is ' her than the maximum permissible velocity this.can berediced by using a longer span bridge. Shouldthis turnout to uneconomical, bed protectionshould s be provided.

9 Computation of Back Water Curve

When the crossing at the bridge Bite is constricted dire to the construction of a new bridgb, back water will be resulted causing a rise in water level above the calculated water level.This rise in water level (if it occurs) has to be taken into account in considering the deck level of the proposed bridge.This computation may not be necessary if there is no constriction causes by the new bridge.Steps for. such computation are available in the DID manual for 'Urban drainage design standard and procedures for Peninsular Malaysia'.

10. PRESENTATION OF SKETCH PROPOSAL

At this juncture, we could have arrived at:-'10.1 Proposed deck level (Having

taken into account the depth off standard beams to be used; thickness of deck slab; premix; bearing and amount~of-freeboard)It is JKR practice to allow for a free board of 0.3-1.0m to cater for the debris brought along by the flood water.

10.2 Number of-spans-required-and the length of.each span.

10.3 .Whether .or not-bed protection is required. with these infomation. we should be able to put up a . sketch proposal. This sketch proposal is to be submitted to the client and the D.I.D for approval.


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TABLE 10. PERMISSIBLE VELOCITIES FOR DIFFERENTBEDMATERIALS

NATURE OF BED PERMISSIBLE VELOCITY(ft/s)

CLAY 7

SANDY CLAY 5

VERY FINE SAND 2 TO 3

FINE SAND 3 TO 5

FINE GRAVEL 5 TO 6

ROCKY SOIL 10

ROCK 14 TO 20

GRASS - LINED 7.5

* EXTRACTED FROM DID “ URBAN DRAINAGE DESIGN STANDARD PROCEDURE FOR PENINSULAR MALAYSIA”

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APPENDIX

NOTATIONS AS USED IN THEHYDROLOGICAL CALCULATION .

A = Area of cross section of riverAc = Area of supplying catchmentC = Runoff coefficientD = X (20).- X (2) .F = Land-use FactorFA = Areal Reduction FactorA h = Difference in leveliT = Average intensity of the design rain

storm of return period T years li = Incremental stream lengthL = Length of the main stream/n = Roughness coefficientp = Wetted PerimeterQC = Discharge capacity of a

river cross sectionQ T= Peak Discharge of design flood with

return. period T yearR = Hydraulic RadiusS, = Incremental Stream slopeS = Weighted mean stream slopeSO = Stream slope at bridge sitet = storm durationT = turn PeriodTc = Time of concentrationVm = mean stream velocityv = stream velocityX(T,t) = Rainfall depth of a storm

with an estimated return period of Tyears and having a duration of t hours.

X(T) = Rainfall depth of a storm with an estimated return period of T years the duration of which is specified elsewhere.

REFERENCES

1. T,D. Heiler, Estimation of the Design Rainstorm, D.I.D. Hydrological Procedure No. 1, Ministry of Agriculture and Fisheries Malaysia, 1973

2. T.D. Heiler and Chew Hai Hong, Magnitude and Frequency of Floodsin Peninsular Malaysia, D.I.D. Hydrological Procedure No.4, Ministry of Agriculture and Fisheries, Malaysia, 1974

3. T.D. Heiler, Rational Method of Flood Estimation for Rural Catchments in Peninsular Malaysia, D.I.D. Hydrological Procedure No.

5. Ministry of Agriculture and Fisheries, Malaysia, 1974

4. M.A.W. Taylor and Toh Yuan Kiat, Design Flood Hydrograph Estimation for Rural Catchments in Peninsular Malaysia, D.I.D. Hydrological Procedure No.11, Ministry of Agriculture, Malaysia, 1980

5. K.V. Lewis, P.A. Cassell and T.J. Fricke, Urban Drainage Design Standards and Procedures for Peninsular Malaysia, Ministry of Agriculture and Rural Development,Malaysia 1975.


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C H A P T E R 3 BRIDGE LOADING

(A) Unlike in the design of Buildings where there is a complete and comprehensive code of practise, no such code for the design of concrete Bridges,ekist until recently. The recentlypublished BS5400, for the design and construction of concrete Bridges, is yet to be adopted by the Bridge Unit Until such time, the design of bridges will be in accordance with BS 153: Part 3A(Loads) : 1973 and the C.P.114 (The elastic analysis method).Amendments and up-dating of the various a clauses in the BS 153 are carried out by the Ministry of transport.(United Kingdom) from time to time and are published in the Technical Memorandum. As such, when referring to the BS 153 for loading, the current Technical Memorandum must also be refered to in conjuction with-the BS153.

(B) Loads Acting an a Bridge Superstructure

The following Loads are to be taken into consideration when designing a bridge. They are:

(i) Dead LoadDead Loads consist of structural dead Loads and superimposed dead Loads. Structural dead Loads are Loads due to the self-weight of the various structural components of the bridge. It should be noted here that a preliminary estimation of the sizes of the various structural components is necessary at this stage. The superimposed dead load consist of items like road surfacing road furniture, weight of services (water mains, Telecoms cables, electric cables ...... etc). -

(ii) Live Loads (HA Loading and HB Loading)

The Standard normal highway loading is called HA loading and the standard abnormal highway loading, the HB loading. Type HA loading comprises a uniform distributed load combined with a line load across the width of each traffic lane. This loading is considered to be adequate to representthe the effects of three vehicles, each 220 KN in weight, closely spaced, in each of two carriageway lanes followed by 100 KN and 50 KN vehicles. It should be noted here that Type HALoading includes a 25% allowances for impact.

Type.HB loading caters for the safe passage of an abnormally heavy vehicle of up to 180 tonnesgross laden weight with a configuration of wheels and axle as shown:

Type HB loading is usually expressed inUnits per axle.The full type HB Loading (180 tonnes) is commonly expressed as 45 units (1 unit - IOKN).or part of it, 371 units (150 tonnes) or 30 units (120 tonnes).


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(iii) Loads due to centrifugal forceOn elevated roadway structures and bridges carrying highways that have sharp horizontal curvature,centrifugal force must be taken into account. This involves making assumptions about the speed and weight of vehicles, together with the intervals between them where the loaded length allows several vehiclesin line. A judgement may be made on the intervals between vehicles, based on the information about stopping distances given in the highway code. The Technical Memorandum BE 1/77 specifies design forces to cover these conditions in anticipition of the requirements of BS 5400.

(iv) Tractive/Braking Loads

The longitudinal force on a bridge structure result from the traction or braking of vehicles at the level of the carriageway surface. It is applied horizontally to the carriageway surface.

(v) Wind LoadsWind forces though rarely significantin small-span and medium-span bridgeworks, can be critical in bridges like the suspension type where the span is large. Generally any structure which is sensitive to

stability problems will inevitably tend tobe more sensitive-to wind loading.

(vi) Load due to shrinkagey temperature.& creep

These are horizontal loads due to forces generated in the beams/slab caused by shrinkage, temperature changes and creep in the concrete.

(vii) Seismic LoadsThese are loads due to earthquakes. For Bridges designed in this country no seismic force are taken into consideration. The only exception to this, is the Penang Bridge where seismic Loads are considered.

Procedure for determination of loadson Bridge Superstructure

STEP 1Determine the dead loads & superimpose deadloads of all structural components.

STEP IIDetermine width and number of traffic lanes

STEP IIIDetermine live loads'type,HA & HB. '

STEP IVDetermine Tractive load,


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STEP VDetermine movement of beam due to tempera-ture, shrinkage and creep and Ca1c . horiz.load.

STEP VIDetermine loads due to wind forces ,

Guide-Lines for Determination of Loads onBridge Superstructure

Within the normal scope of design work carriedout by the Bridge Section, the loads on aBridge superstructure normally considered are:

(i) Dead Loads(ii) Live Loads(iii) Tractive/Braking Loads

(Longitudinal load)(iv) Wind Loads(v) Loads due to shrinkage, temperature &

creep (S.T.C)

The loads normally not taken into considera-tion are loads due to centrifugal force (exceptfor sharp horizontal curvature) and even moreinfrequently, seismic loads.

However, in special circumstances where abridge is designed to be submerged, then thelateral horizontal force due to the water currentand the bouyant force of the water need to becalculated and taken into consideration.

STEP IDead Loads

The calculations for the dead loads of a bridgesuperstructure is quite straightforward.However a preliminary estimation of the sizesof the various structural components-, thicknessof the deck slab, premix surfacing ... etc isrequired. This can be a problem for thosedesigners attempting bridge design for the firsttime. The importance of an orderly and systematicapproach to the calculations of dead loads can-not be overemphasized. Any haphazard approach may result in a structural componentor item inadvertently left out. A good guide to

follow is provided by the 'Summary ofLoadings on Bridge Superstructure'. It shouldbe noted here i that the total.dead loads are sup-ported equally by the two supports.

STEP IIWidth and number of traffic (design) lanes

Very frequently, views differ on what should bethe carriageway width for live loads (HA &HB) considerations on a bridge and conse-quently, the number of traffic (design) lanes. Itis the writerts opinion thatthe carriageway width of a bridge should be theclear distance between raised kerbs. Howeverthe more recent standards issued by the Roadprdt\ch does not encourage the use of Kerbsbut instead adopts 'Road Edge Stripping' todemarcate the traffic lane from the cycle/pedestrian lane. In such cases, the carriagewaywidth should include the cycle/pedestrianlanes. The justification for the inclusion being,there is a very likely possibility of an errantvehicle going onto the cycle/pedestrian lane, inthe absence of road kerbs. (see fig. 1 and fig.2).

In the determination of Live Loads, two impor-tant items need to be obtained initially.

(i) The number of traffic (design) lanes

(ii) The width of each traffic (design) lanes

There are two cases of carriageway width toconsider:

(i) Bridge with carriageway width of 4.60 m or more

(ii)Bridge with carriageway width of less than 4.60 m

In case (i) the number of traffic (design) lanesis obtained by dividing the carriageway widthby 3.80 m and rounding up to the next wholenumber.


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Example

Assume carriageway width = 7.5 m From Table in B.S. 153: Part 3A:1972 (pg. 5)Number of traffic lanes = 3width per lane = 7.5 = 2.5 m

3In case (ii) the number of traffic (design) lanesis obtained by dividing the carriageway widthby 3.0 m. This implies that there will be frac-tional lane and the loading on the fractionallane will be proportional to the full lane.

ExampleAssume carriage width = 4.20m ,

Number of lanes = 4.2 lanes3

Width per lane = 4.2 = 3.0 m.1.4

At this juncture, it is appropriate to give someclarification on the concept of traffic lanes.Rightfully, when designing, the lanes referredto should be called Design Lanes rather thantraffic lanes so as.to distinguish it from trafficlanes in the context of Road design.

From the above example Of carriageway widthof 4.20m, it is clear why the distinctionbetween the two must be made. In that exam-ple we have the number of lanes (for LoadingConsideration) = 1.4 lanes, which would not bea possible number in Road Design. It would,in Road design, be a one lane or two lane road-way. This clearly demonstrates that the numberof traffic (design) lanes of a bridge need notnecessary be equal to the number of trafficlanes of a roadway.

STEP IIILive Loads HA & HB HA Loads

When considering HA (normal live load)

loads, it is important to note HA loadsonsist of three components; (i) HA-udl load

and (ii) HA-KEL load (See fig. 3) and (iii) HA-Wheel loads. This implies that the HA-UDLload is uniformly distributed bothways equallyi.e. longtudinally and across the width of thedesign (traffic) lane. The HA-KEL load is aline load acting across the width of the design(traffic) l6e. An important point to note here isthat the HA-KEL load is a movabl load (alongthe span). The HA-KEL load must be placed insuch a position so as to cause worst effects. Forexample, in the design of abutment or pier theHA-KEL must be positioned over the abutmentor pier. In beam design however, the HA-KELmust be positioned mid-span.

To wheel loads each 112KN force in line trans-versely to the direction of traffic flow spaced at0.90m centres and having a contact area of 375mm x 75 mm, the smaller dimension being inthe direction of travel, to be used in the follow-ing cases:

(a) Where the member supports a small area of roadway such that it may be called on to carry the weight of one or two wheels, and where the proportion of distributed load and knife edge load which would be allocated to it is small and on cantilever projections not exceeding 1.80m.

(b) Where deck slabs are designed assupported on all four sides and the distance between supports in one directions is less than twice the distance in the other direction.

The values for HA-udl (spanwise) and HA-KEL (across the width of lane) are obtainedfrom Table 1 and Fig. 1 of B.S. 153. Howeverthe values obtained need to be reduced by thefactor 3 for lanes less than 3.Om width for HA-UDL values (W= width of design lane) and forHA-KEL the values are 40KN/m (acrosswidths/lane), for lane width less than 3.Om and120 KN per lane for,lane width greater than3.0m. .


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Bridge with two or less design lanes shall beloaded with the full HA-UDL and HA-KELloads. However for every additional designlane above two lanes, it shall be loaded withone-third (1/3) the full intensify. (see Fig.4).The relevant clause pertaining to this rule isclause 4.1.3. Of the B.S. 153.

The following examples will illustrate moreclearly the computations for HA-UDL and HA-KEL loads.

Case (i) Design (traffic) lane width 3.0m. orless Assume:

(a) Design' (traffic) lane width = 2.70m(w)

(b) Number of Design (traffic) lanes = 3(c) Span of Bridge = 31.O m

From Table 1 and Fig.1 of B.S. 153,HA-UDL = 28.5 KN/m (spanwise, per lane)

HA-UDL (Reduced) = 28.5 x 2.70 = 25.65 KN/m (per lane)

3

HA-KEL (Fig.1) = 40 ICN/m (across width oflane)HA-UDL.(for first two lanes) = 25.65 x 31.0

x 2 = 1590.3 KN

HA-UDL (for third lane) = 25.65 x 31.0 x1 x 1/3

= 265.05 KN Total HA-UDL = 1590.3 + 265.05

= 1855.35 KN

HA-KEL (for first two lanes) = 40 x 2.70 x 2

= 216 KN HA-KEL (for third lane) = 40 x 2.7 x 1 x

x 1/3= 36 KN

Total HA-KEL = 216 + 36 = 252 KN

Case (ii) Design (traffic) lane width greaterthan 3.Om assume:

(a) Design (traffic) lane width = 3.2m (w)

(b) Number of Design (traffic) lanes = 3(c) Span of Bridge = 31.0m.

From Table 1 and Fig. Y of B.S. 153,HA-UDL = 28.5 KN/m (per lane) - HA-KEL(Fig.1) = 120 KN per lane.

HA-UDL (for first two lanes) = 28.5 x 31.0 x 2.

= 1767.0 KN HA-UDL (for third lane) = 7R-5 x31.0 x 1/3

= 294.5 KNTotal HA-UDL = 1767 + 294.5

= 2061.5 KN

HA-KEL (f6r first two lanes) = 120 x 2 = 240KN HA-KEL (for third lane)

= 120 x 1 x 1/3 = 40 KNTotal HA-KEL = 240 + 40

= 280 KN

HB Load

The configuration of axles and wheels of a HBvehicle is as shown in Fig. 5. The load per axleis 450 KN and the total weight of the HB vehi-cle is 1800 KN. Very often the full weight ofthe HB load is also expressed as units per axle.The full HB load is referred to as 45 units . (1unit = 10 KN) or part of it, say, 37J units HB.(375 KN/axle).

Like the HA-KEL, the HB load is a movableload. For the design of abutment/pier or beams,the vehicle must be placed in such a position soas to cause the most adverse effects. (SeeFig.6).

In Bridges designed (checked) for HB loads,the Live Loads to be adopted for design will beeither loads due to HA (Normal) or HB (abnor-mal) loads, depending whichever is greater.

In Bridges designed (checked) for HB loads,the Live Loads to be adopted for design will beeither loads due to HA (Normal) or HB (abnor-mal) loads, depending whichever is greater.


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STEP IVDetermination of Tractive/Braking Load

This is horizontal force acting longitudinally ona bridge deck generated by sudden braking ortraction of vehicles (see Fig.7) on the bridge. Itis even more severe if the vehicles are heavy.The determination of this Tractive load is sim-ple enough and the relevant clause in clause 10of the B.S. 153. However the present JKRPractice predetermines a maximum value of253 KN for tractive load for both HA and HB(45 units) Loadings.

This is a slight departure from the B.S. 153where the maximum load is 450 KN. The reason for this adoption of a smaller load is, inmy opinion,. due to the present system of control and approval of passage of HB- Classof vehicles over a public road bridge. Anyheavier than normal load intending to use anybridge has got to seek prior approval of JKRauthorities. A condition normally imposed willbe that the abnormally heavier vehicle to travelalong the bridge centre-line at a very slowspeed. No other vehicles will be permitted touse the bridge during this time. In such circum-stances, the force due to sudden braking andtraction is reduced to a minimum or none at all.Hence the adoption of a smaller load is justi-fied.

STEP VLoads due to movement of beam caused bytemperature, shrinkage and creep

They are horizontal forces acting longtudinallyon a bridge generated by movement of beamcaused by temperature, shrinkage and creep.

The temperature and shrinkage coefficientsadopted may be assumed to be universal valuesbut the creep coefficients is dependent on con-crete cube strength and cube strength at transfer(for prestressed beams).

How much of shortening caused by shrinkageand creep that has occured at the time of casting of the beams and prestressing, is more

speculative than anything else. It is not uncommon to see designer's assuming avariety of figures. In the Bridge sectin we nor-mally assume two-thirds (2/3) shrinkage andhalf (1) creep has(already occurred at the timeof placing of beams. (See Fig.8).

Therefore the actual beam movement,= Temperature shortening + shrinkage + creep

3 2

Knowing the actual beam movement, Plan areaof elastomer and it's-shear Modulus, (for thatparticular 'Hardnesl';of elastomer) the horizon-tal force due-to shrinkage, Temperature andCreep, (commonly abbreviated to S.T.C.) canbe determined. (See Fig.9). Shrinkage andcreep can act in.only one 'direction but temperature can act in ;either direction,longitudinally.

STEP VILoads due to Wind Forces

Generally, structures that possessed stabilityproblems, like the suspension bridges, will besensitive to wind loads. For the types ofbridges designed in this section, wind loads arenot critical but nevertheless they have to betaken into consideration of design purposes.

Only the longtudinally component of the lateralwind force is taken into consideration. The lat-eral horizontal'wind force is normally omitted-due to the fact the ratio of the total verticalforces to the lateral horizontal forces is so largethat stability of the structure can be provided bythe sheer weight (Live Dead Load) of the struc-ture itself.

In the calculations for wind forces the area ofsuperstructure (AW/s) normal to the directionof the wind in the windward side will berequired. This AW/s will normally be made upof the height of the beam thickness of deck slaband the edge kerb, in the case of the bridge isof the metal. railings type or plus concreteparapet height if it is of the concrete parapettype.


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The height of the live load is taken as 2.50mfrom the top surface of the deck and shall beassumed to occupy the span of the bridge. -Thus, the area of live load (AL.L.) normal tothe direction of the wind is = 2.50 x span ofbridge. Case should be taken to ensure thatscree,ing effect of the concrete parapet on thelive load is taken into conside-ation. Hence theAL.L. always refer to the net exposed area oflive load. In the case where the concrete para-pet is used, then AL.L,= (2.50-0.80) x span ofbridge. (Assuming concrete parapet heightapprox. = 0.80m).

Another factor just simply referred to as 'n' inthe B.S. 153, (perhaps should be termed as theleeward side factor) is simply defined as theratio of the distance between the windwardgirders (beams) to the leeward girders (Beams)to the height of the windward girder. Thisfactor, n/16 , is always less than unity and isapplied at the leeward side when determiningwind forces on it. The following shows the derivation of the formulas shown i/n Fig. 10.

A. Unloaded Case

From B.S. 153, Wind Pressure = 1.4 KN/m2

on windward side, The lateral wind force= 1.4 x Aw/s on leeward side the lateral windforce = 1.4 x Aw/s x n

16 Since the two forces act in the same direction,the total lateral wind force = 1.4 x Aw/s x n/16+ 1.4 x Aw/s = 1.4 x Aw/s (1 + n/16)The longtudinal wind Force is simply taken as=1/4 of Lateral Wind Force.

B. Loaded Case

From B.S. 153, Wind Pressure = 0.7 KN/m2 .Here however, the area providing resistance tothe wind will be (Aw/s + ALL ).As before;The total lateral Wind Force = 0.7 (Aw/s +AL.L) (1 + n/16). In this case, the B.S. 153states that the longtudinal wind force should betaken as a.quarter of the lateral wind force on

the superstructure and half of the lateral windforce on the live load.

Longtudinal Wind Forcez[( 1/4 x 0.7 x Aw/s)+ (1 /2 x 0.7 x AL.L) ] (1 + n/16)

References .B.S. 153: Part 3A = 1972 (Loads)CONCRETE BRIDGE DESIGNER'SMANUALE. PENNELLS - 1981LECTURE NOTES ON BRIDGE LOADINGS BRIDGE DESIGN COURSE - BANGI 1983.


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BS 153.: Part 3A: 1972British Standard Specification forSteel girder bridges Part 3A. Loads

1. Scope of BS 153 .

This specification is primarily intended toapply to the superstructure of simply supportedsteel bridges of spans up to 100 m. Whereappropriate, the requirements of the specifica-tion may be adopted for larger spans or othertypes of steel bridges, but care should be taken,in these circumstances to make whateveramendments are necessary for fixity at the sup-ports, continuity and other indeterminate orspecial conditions, such as, for instance, mayapply to opening bridges.

2. Forces 'to be taken into account

For the purpose of computing stresses the following items shall, where applicable; betaken into account:(1) Dead load.(2)Live load.(3) Impact effect.(4) Lurching effect.(5) Nosing effect.(6) Centrifugal force. (7) Longitudinal force. (8) Wind pressure effect (9) Temperature effect.(10) Resistance of expansion bearings to movement. (11) Forces on parapets.(12) Erection forces and effects.(13) Forces and effects due to earthquakes, icepacks, subsidence and other similar causes.

Subject to the provisions of other clauses, allforces shall be considered as applied and allloaded lengths chosen in such a way that themost adverse effect is caused on the memberunder consideration.

3. Dead load

The dead load is the weight of the structure andany permanent loads fixed thereon. The dead

load initially assumed shall be checked afterthe design is made and the design shall berevised as found necessary.

In determining the dead load, actual ascertainedunit weights shall be used, but if these are notavailable unit weights as given in 13S 648 maybe used, as appropriate.

4. Live load .

The live load is the weight of traffic and shallbe of the type and magnitude specified. Thefollowing standard loadings shall be adoptedwhere appropriate:

4.1 Standard highway loading4.1.1 Loading. Standard highway loadings

are given in Appendix A.

These are:Type HA. Equivalent lane loading which is the normal design loading for Great Britain but may be varied in intensity whereconditions are other than, those prevailing inGreat Britain.Type HB. Abnormal unit loading. To be used when specified by the appropriate authority. In Great Britain 45 units shall be taken for bridges carrying the heaviest classof load This is an idealized load which allows for the weight of tractors accompanying trailers.

4.1.2 Width and number of traffic lanes to be used in conjunction with standard highway loadings .

4.1.2.1 Bridges having a carriageway width of 4.60 m,or more. Traffic lanes shallbe taken to be not less than 2.30 m nor more than 3.70 m wide. The carriageway shall be divided into the least possible number of traffic lanes having equal widths as follows:


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4.1.2.2 Bridges having a carriageway width of less than 4.60 m. Where the carriageway on a bridge is less than 4.60 min width it shall be taken to have a number of traffic lanes.

= width of carriageway in metres ----------------------------------------

3.004.1.2.3 Where dual carriageways are carried

on one single superstructure, the number of lanes on the bridge shall be taken as the sum of the number oflanes in each of the single carriageways, as provided in the table above. Where hard shoulders and marginal strips are provided these shall be considered as forming part of the carriageway and thenumber and width of traffic lanes calculated accordingly.Where marginal strips are provided without hard shoulders the number of traffic lanes shall be calculated after deducting the widths of the marginal strips from the overall width of the carriageway between the verges or raised 'kerbs; the intensity of loading on the marginal strip shall be taken as equal to that for the adjacent carriageway lane, except where the adjacent arriageway lane carries HB loading, in which case the marginal strip is unloaded.

4.1.3 Application of standardloading on a single superstructure

Type HA loading Type HA loading shall be taken. to occupy one carriageway lane and to be uniformly distributed over the full width of the lane.

Two lanes shall always be considered as occupied by full Type HA loading, while all other lanes shall be considered as occupied by one-third thefull lane loading, except where otherwise specified by the appropriate authority.

Type HB loading. One lane shall be loaded with Type HB loading only.

Where one carriageway only is carried on a superstructure, all other lanes shall be considered as occupied by one-third of the full lane loading, except where otherwise specified by the appropriate authority.Where dual carriageways are carried on one single superstructure two lanes on the carriageway not carrying HB loading shall be taken as occupied with full HA loading. All other lanes- shall be taken as carrying J, HA loading.

4.2 Standard railway loading

Standard railway loadings are given in Appendix B, in imperial units only. Where the remaining calculations are in SI units, the values obtainedain imperial units shall be converted into SI units using the appropriate conversion factor.

These are:

Type RA. British Standard unit loading, for various gauges.Type RB. Total uniformly distributedload, including impact, for gauges of4 ft 81 in (1.432 m) and over.


Carriageway width (m) No.of lanes

4.60 up to and including 7.40




2

3

4

5

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BS 153: Part 3A: 1972

This loading is based on the Bridge Stress Committee's report of 1928, a brief pricis of which is given in Appendix D. It is suitable for railways in Great Britain and abroad with agauge 4 ft 81 in (1.432 m) and over and withlocomotive and track characteristics similar tothose obtaining on the main railways in GreatBritain.

4.3 Standard footway loading .

The live load due to pedestrian traffic shall be treated as uniformly distributed over the footway. For loaded lengths upto and including 23.0 m it shall normally be taken as 4 kN/m' and for lengths over 23.0 m as the standard uniformly distributed loads given in Fig. 1 multiplied by a reduction factor of 4.0/31.5. Where crowd loading is likely the live load for the design of members exclusively supporting or forming the footway shall be taken as 5 kN/m'.In the case of highway bridges each part of the footway shall be capable of carrying a wheel load of 40 M, which shall be deemed to include impact, distributed over a contact area 300 mm in diameter; the working stresses shall be increased by 25 % to meet this provision. This provision need not be made where vehicles cannot mount the footway.

5. Impact effect on highway bridgesWhere Types HA ant"HB loadings given in Appendix A are not adopted,the allowance for impact on highway bridges shall be to en as follows:

(1) An impact allowance of 25 % shall be added to the axle-load, or (where there is more than one lane oftraffic) the pair of adjacent wheel loads, which produces the greatest bending moment or shear, as the

case may be, and o the condition of loading for which the member being considered is designed.

(2) Where the loaded length required to produce the maximum stress in any member exceeds 30.0 m impact shall be ignored.

No addition for impact shall be made to the live load due to pedestrian or equivalent lighttraffic.

6. Impact effect on railway bridges

A propriate additions shall be made to the live load specified in 4 for impact effects caused by the hammer blow of locomotives, rail joints, and track and wheel irregularities.In determining these additions due consideration shall be given by the engineer to the standard andmaintenance of track and roiling stock, the types and characteristics of locomotives, and the. type and /characteristics. of the bridge.Type RB loading, which is suitable for the main line railways of Great Britain and other railways having similar locomotive and track characteristics, already includes an allowance for impact and co further additions shall be made. For all other loadings, including type RA, the additions for impact shall be specified by the engineer. For his guidance three methods of calculating the additions, those of Foxlee and Greet,the Government of India and the American Railway Engineering Association, are described in detail in Appendix C.

7 Lurching on railway bridges

A separate allowance shall be made for lurching, unless this has already been included in the impact effect. 'Lurching results from the temporary transfer of


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BS 153: Part 3A: 1972

part of the live loading from one rail to the other, the total load on the track remaining unaltered. The transfer shall be taken to increase the load on the rail which most adversely affects the member under consideration.The proportion QL of live load on one rail so transferred shall be calculated from the expression.

160k nQL = ---------

I +100where k is a coefficient depending on

the type of spring suspension, the weight and height of the rolling stock, and the type of construction and lateral rigidity of the bridge structure;

n is the number of revolutions persecond of the driving wheels of the locomotives (see Fig. 6, Appendix B);

1 is the effective span in feet, as defined in 1.4 of Part 4.

NOTE. For conditions corresponding. to thoseruling on the railways of Great Britain (4 ft81/2 in gauge = 1.432 m gauge), and providedthe structure is adequately stiffened laterally,k = 1/24 and n = 6 for maximum speed, butwith a maximum value of QL of 0.25. For conditions other than those ruling on the railways of Great Britain, and where provisionfor a greater lurching effect is necessary, it isrecommended that the value of the coefficientk be increased but to not more than 1/15 with amaximum value for the factor QL of 0.40.Where a member supports or assists in support-ing more than one track, provision for theeffect of lurching need only be made in respectof one of the tracks where these are two. or inrespect of alternate tracks where there are morethan two, the track or tracks selected beingthose on which the transfer of the load has thegreatest effect on the member.Lurching need not be taken into account in the

case of an inner main girder assisting in sup-porting more than one track.No addition for impact shall be made to thelurching effect.

8. Nosing on railway bridges .An allowance shall be made fornosing, and this shall be taken as a single force of 10 tonf, acting horizontally, in either direction, at right angles to the track, at the rail level and at such a paint in the span as to produce the maximum effect in the member under consideration. This value is appropriate to the conditions obtaining on railways in Great Britain. In other cases the amount of force may be amended at the engineer's discretion.Vertical effects shall be disregarded. : On multi-track bridges, a single force as specified above shall be deemed sufficient.

9. Centrifugal force on railway bridges

Where the track or tracks are curved, allowance for centrifugal action of the moving loads shall be made in designing the members, all tracks on thestructure being considered as occupied. The centrifugal force due to the load pertrack shall be calculated from thefollowing formula:

w v2

C = -----------15R

where C = the centrifugal force per linear foot considered as a moving load, acting at a height of 6 ft (1.83 m) above the level of the rails, unless otherwise specified by the engineer;

w = the equivalent distributed live load, without impact, per linear foot per track;

v = the allowable maximum speed of the train in miles per hour, as specified by the


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BS 153: Part 3A: 1972

engineer; and R = the radius of the track curve

in feet.No addition for impact shall be made to the centrifugal force.

10. Longitudinal force on highway bridges

The following longitudinal force resulting from the traction or braking of vehicles shall be taken as acting horizontally at the level of the carriageway surface, and having the following values for all widths of bridge. The force shall be applied over an area 3.00 m wide by 9.00 m long, or the length of the bridge, whichever is less, and in that position which will have the worst effect on the member under consideration.

No increase for impact effect shall be made tothe stresses due to longitudinal forces. Onlyone such force shall be considered.

11. Longitudinal force on railway bridges

Provision shall be made for the forces due to traction and the application of brakes. These forces shall be considered as acting-on the rail, and, for the purpose of the

design of the structure, shall be takenas the larger of:

(1) A force due' to traction of 20 % of the total axle loads on the coupled or driving wheels on one track without impact. When type RB loading is used, 20 units of type RA loading shall be taken for this purpose.

(2) A force due to braking of 10 % of the total load on one track without impact.

Where the structure carries two tracks, one up and one down, both tracks shall. be considered as being occupied simultaneously, and the force due to braking shall be applied to one track and, the force (in the same direction) due to traction to the other.

Where the structure carries more than two tracks, the longitudinal forces shall be considered as applied to two tracks only, unless otherwise specified by the engineer, the worst case being taken as'regards its effect on any part of the structure.

Some relief in the effect of the longitudinal force on the bridge and its supports may be taken into account where the tracks are capable of transmitting part of these forces toresistances outside the bridge structure.No addition for impact shall be madethe longitudinal force.


Type HA Loading Type HB Loadingfor 45 units

Span up 3.00m

Spans above3.00m

100 kN

100 KN plus 17kNfor each metre ofspan over 3.00mm but notexceeding 253 kN

}}}}450kN for allspans}}}

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BS 153: Part 3A: 1972

12. Wind pressure effects

12.1 General

Where the effect of wind has to be taken into consideration, it shall be treated as a moving load (i.e. taken of such length along the span as to produce the maximum stress in the member under consideration) acting at the centroids of the exposed areas as defined below.

The maximum effects from the wind blowing in either lateral direction on the loaded or unloaded structure., shall be taken, having regard to the disposition of the live load.

For conditions normally prevailing in Great Britain the wind pressures specified below shall be used, but where owing tothe position of the bridge or any special conditions the assumed wind speeds cannot be realized ormay be exceeded, the engineer shall at his discretion specify different values. For this purpose the wind pressure shall be assumed to vary as the square of the wind speed.

12.2 For maximum lateral effect

12.2.1 On unloaded structures. A wind pressure of 1.4 kN/m2 corresponding to a wind speed of 40 m/s shall be '. taken as acting horizontally and normal to the sides of the bridge on a total exposed area of the superstructure made up of the following areas as applicable:

Windward girder, deck end bracing. The net exposed area in normal projected elevation of the windward girder, deck construction, bracing and parapet.Leeward girders. The following fractions (not exceeding unity) of the net exposed area in normal projected elevation of the leewardgirder :

n /16 when the windward girder is a plate girdern / 16 + 0.5 when the windward girder is a trussed girder

where n = ratio of distance, centre to centre between the windward and outermost leewardgirder, to the depth of the windward girder.

Where there are more than two main girders, only that fraction ofthe area of the outmost leeward girder as calculated above shall be taken.

In cases where a leeward girder projects in elevation beyond the windward girder, the full net exposed area.,of the projection as seen in elevation shall be treated as subject to full wind pressure.

12.2.2 On loaded structures. In arriving at the total effective area exposed to wind on a loaded structure, allowance shall be made for the screening effect, based on projected areas, of the structure on the live load, or of the live load on the structure, or of live loads on each other:


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BS 153: Part 3A: 1972

12.2.2.1 Highway and jootway bridges.A wind pressure of 0.7 kN/m2,corresponding to 28 m/s, shall be taken as acting horizontally and normal to the sides of the bridge on the exposed area of the superstructure (calculatedas in 12.2.1). and of live load taken as a single vertical plane surface having a continuous height of 22.500 m above the carriageway or.1,25 m above footway and cycle tracks, as applicable.

12.2.2.2 Railway bridges. A wind pressure of 1.4 kN/m= (30lbf/ft2) corresponding to a wind speed of 40 m/s, shall be taken as acting horizontally and normal to the sides of the bridges on the exposed. area of the superstructure (calculated as in12.2.1) and of live load taken as a single vertical plane surface having a continuous height of 3.75 m (12 ft) above. the rail.

12.3 For longitudinal effect

A longitudinal wind force shall be combined with a corresponding lateral wind force equal to half the total lateral force given in 1.2.2 and the two shall be distributed compatibly.The longitudinal wind forces shall be determined as follows:

(1) For plate girder bridges: a quarter of the total lateral wind forces on the superstructure in the unloaded condition (see 12.2.1)or a quarter of the total

lateral wind forces on the superstructure and half the total lateral wind forces on the live load,in the loaded condition (see 12.2.2).

(2) For trussed girder bridges: half the total lateral wind forces on the superstructure in theunloaded condition (see 12.2.1); or, half the total lateral wind forces on the superstructure and live load, in the loaded condition (see 12.2.2).

12.4 For maximum overturning effectOn the bridge and its supports, the following shall be taken into account :

(1) In addition to the lateral and longitudinal wind forces specifiedabove, an upward verticalpressure of . 0.24 kN/ml acting over the net exposed area of the bridge in plan.

(2) In considering the overturning effect due to wind on live load, the live load shall consist of standard loading or of unloaded wagons or vehicles of the lightesttare, whichever produces the maximum overturning effects. The latter shall be taken as not greater than 12 kN per linear metre of bridge for railway bridges and not greatet than 6 kN per linear metre of bridge for highway bridges.

13. Temperature effectAllowances shall be made for the forces resulting from the following conditions:

(1) Any portion of the superstructure being restrained from moving


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BS 153: Part 3A: 1972

when subjected to variations of temperature. For this purpose in Great Britain a minimum of -7 ° C and a maximum between 27 ° C and 49 ° C, depending on the location of the structure, shall be taken. Elsewhere the temperature limits shall be based on local conditions.

(2) Any portion of the superstructure being at a temperature different fromthe rest of the structure, due to the effect of sun and shade. For this purpose the maximum difference of temperature shall be taken as 8 ° C.In determining forces andmovements due to change of temperature the coefficient ofexpansion of steel shall be taken as 1.17 x 10-5 per ° C.

14. Frictional resistance of. expansion bearings

For expansion and contraction of the structure due to variations of temperature or to other causes, the forces due to friction on the expansion bearings under dead load only shall be taken into account and the following coefficients of friction shall be used:

For roller bearings with 1 or 2 rollers- 0.01

For roller bearings with 3 or more rollers - 0.05For sliding of steel on hard copper alloy bearing - 0.15For sliding of steel on cast iron or steel

-0.25

15. Forces on parapets

15.1 Footbridge parapets .

Consideration shall be given to the strength and stability of parapets.

Parapets may be subject to horizontal loads acting at a height of 1.00 m above the level of the footway, rangingfrom 0.7 kN per metre to 1.4 kN per metre, according to circumstances. Themaximum load will only be encountered in extreme cases of crowd loading.

The value of the loading shall be taken at the discretion of the engineer'.

15.2 Motorway and other highway bridge parapets

Reference should be made to the Ministry of Transport memorandum on the subject.

16. Combination of forces

The following combinations of forces shall be considered:

(1) The worst combination possible of dead load with live load, impact, lurching and centrifugal force.When a member whose primary function is to resist longitudinal and nosing forces due to live load is under consideration the term live load shall include these forces.

(2) The worst combination possible of any or all of the'forces listed under (1).to (11) inclusive in 2.

(3) The worst combination possible of forces during erection: .

(4) The worst combination possible of any or all of the forces listed in 2, at the discretion of the engineer. 17. Erection forces and effectsThe weight of all permanent and temporary material, together with all other forces and effects which can operate , or. any part of the structure during erection, shall be taken into account.


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BS 153: Part 3A: 1972

18. Anchorage .

The stability of the structure and its parts shall be investigated and weight oranchorage shall be provided so that the least restoring moment, including anchorage, is not less than the sum of:1.1 x dead load overturning moment,and 1.4 x overturning moments due to applied loads.Account shall be taken of possible variations of dead load for repair or other temporary purposes to ensure stability at all times.This margin of stability ifs so far as stresses are concerned shall be deemed to be covered in respect of.all parts. of the structure which have been designed for their working loads to the permissible stresses in this British Standard. In complying with therequirements of this clause it. is necessary to ascertain that the resulting pressures and shears deemed to be communicated by the bearings to the substructure will not produce failure.

19. Clauses to be referred to the engineer

The following clauses in Part 3Acontain points on which the decision of the engineer is required and concerning which information-is to be supplied at the time of inviting tenders.Clauses 4.1.1, 6, 7, 8, 9, 11(2), 12.1, 13(1), 15,16(4).

Appendix A

Standard highway loading

A.1 Type HA loadingType HA loading consists of (1) and (2), or (3),viz.:

(1) A uniformly distributed lane loading. The values for this load per linear metre

of traffic lane are given in Table I and Fig. 1.

(2) One knife edge load uniformly distributed across the width of the traffic lane. The values of this load, which shall be applied in accordance with A.3.I, are given in Fig. 1.

(3) Two wheel loads each 112 kN force in line transversely to the direction of trafficflow spaced at 0.90 m centres and havinga contact area of 375 mm x 75 mm, the smaller dimension being in the direction of travel, to be used in the following cases:

a. Where the member supports a small area of roadway,such that itmay be called on to carry the weight of one or two wheels, and where the proportion of distributed load and knife edge load which would be allocated to it is small and on cantileverprojections not exceeding 1.80 m.

b. Where deck slabs are designed as supported on all four sides and the distance between supports in one direction is less than twice the distance in the other direction.In this respect the edge stiffening of slabs as required by A.3.9 of this appendix shall not be deemedas providing adequate support forthis purpose.

A.2 Varied intensities of type HA loading .

Where a different intensity of loading isrequired, Type HA loading may be varied pro-portionately, each item of the loading beingvaried pro rata.When making any reduction it should be bornein mind that an impact allowance of 25 % asspecified in A.5.1 has been taken into accountin this loading. This allowance is consideredadequate for conditions in Great Britain, butmay not necessarily be sufficient elsewhere.


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BS 153: Part 3A: 1972

A.3 Application of type HA loading

A.3.1 The knife edge load shall be taken as acting as follows:

A.3.1.1 On reinforced concrete slabs effectivelysupported on two sides and on cantilever slabsexceeding 1.80 m. In a direction parallel to thesupporting members.

A.3.1.2 On longitudinal girders, stringers, etc.In. a direction at right angles to the member.

A.3.1.3 On cross members, including trans-verse cantilever girders. In a direction in linewith the member.

A.3.2 Where longitudinal members are spacedat less than half the width of the lane the load-ing to be taken on these members shall be thatappropriate to a half lane width.

A.3.3 The total end live load shear on any lon-gitudinal beam shall be taken as not lessthan.90 kN per metre width of carriagewaysupported by the member.

A.3.4 No allowance shall be made for impactor dispersal of load in respect of the distributedload or knife edge load.

A.3.5 No allowance shall be made for impactunder the wheel loads.

A.3.6 Dispersal under the wheel loads, where itcan occur, shall be taken at 45°.

A.3.7 It shall be permissible in considering theeffects of the 112 kN loads to allow a 25 90overstress.

A.18 Reinforced concrete slabs shall be-designed on the basis of 1 m wide strips carry-ing one-third of the appropriate lane loading asgiven in Table- I and Fig. 1 except when usingthe wheel loads A.1(3).

Distribution reinforcement transverse to thespan of the slab shall be provided throughout.For spans not exceeding 6.00 m its amount inthe area of sagging moment shall be sufficientto resist not less than 5090 of the maximumdive load moment at the sections consideredand it shall be so placed as to ensure effectiveresistance to transverse bending.

A.3.9 Where the wheels of vehicles using thebridge can travel on or near the unsupportededge parallel to the main reinforcement of slabdecks, edge stiffening or its equivalent shall beprovided capable of carrying live load asdescribed below, in addition to the live loadwhich would normally be allocated to it.

A.3.9.1 Longitudinal slabs. That proportion ofloading from Fig. 1 and Table 1 appropriate toa strip of slab having a width equal to one-quarter of the span, but not more than 1.50 mnor less than 0.60 m.Alternatively, the slab may be extended beyondthe edge of the carriageway for a distance equalto one-quarter of the span, but not more than1.50 m nor less than 0.60 m.

A.3.9.2 Transverse slabs. That proportion ofloading from Fig. 1 and Table 1 appropriate toa strip having a width equal to two-thirds of thespan.

A.3.10 Where elements of a structure. can sus-tain the effects of live load in 'two ways, i.e., aselements in themselves and also as parts of thestructure (as, e.g., the top flange of a box girderfunctioning as a deck plate), the elements shallbe designed to resist the sum of the effects ofthe appropriate loading for each condition.Where the wheel loads of A.1(3) are used, the25 % overstress permitted in A.3.7 shall beapplied in considering the sum of the effects.


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LoadedLength

U.D.L forbeams permetre of lane

U.D.L forlongitudinalslabs permetre of lane

U.D.L fortransverseslabs andcross girdersper metre oflane

Loadedlength

U.D.L forbeams permetre of lane

U.D.L for longitudinalslabs permetre of lane

U.D.L fortransverseslabs andcoss girdersper metre oflane.

m1.001.251.501.75

2.002.252.502.75

3.003.253.503.75

kN318.6233.7179.4146.4

126.6112.8101.792.4

84.677.472.368.4

kN318.6233.7179.4139.5

107.185.572.064.5

58.553.449.245.3

kN282

153.6113.489.4

72.662.755.248.6

45.041.737.736.3

m4.004.254.504.75

5.005.506.00

6.50-23.0

kN64.860.957.052.8

49.241.133.031.5

kN42

39.036.335.1

33.932.131.531.5

kN34.233.031.831.5

31.531.531.531.5

Table 1. Highway loading. Type HA

Equivalent uniformly distributed load (U.D.L) to be used in conjunction with the knife edgeload (see Fig. 1)

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Loadedlength

Force Loadedlength

Force Loadedlength

Force Loadedlength

Force

m24.025.026.027.0

28.029.030.031.0

32.033.034.035.0

36.037.038.039.0

40.041.042.043.0

44.045.046.047.0

48.049.050.051.0

kN/m31.230.830.430.0

29.029.328.928.5

28.227.827.427.0

26.826.626.226.0

25.725.425.224.9

24.624.324.023.8

23.523.222.922.6

m52.053.054.055.0

56.057.058.059.0

60.061.062.063.0

64.065.066.067.0

68.069.070.071.0

72.073.074.075.0

76.077.078.079.0

kN/m22.322.021.821.5

21.321.120.920.7

20.620.420.220.0

19.819.719.619.4

19.319.119.018.9

18.718.618.518.3

18.218.117.917.8

m80.082.084.086.0

88.090.092.094.0

96.098.0100105

110115120125

130135140145

150155160165

170180190200

kN/m17.717.417.217.0

16.816.616.416.2

16.116.015.915.6

15.315.1214.914.7

14.514.314.114.0

13.813.713.613.5

13.413.112.912.7

m220240260280

300325350375

400425450475

500525550575

600625650675

700725750775

800850900

kN/m12.211.711.310.9

10.610.19.89.5

9.08.68.48.2

7.97.77.47.3

7.17.06.86.7

6.66.56.46.3

6.15.95.8

Note to Table t and Fig. iNormal loading (Type HA) approximately, represents the effect of three vehicles, each 22 tonne(220 kN) in weight, closely spaced, in each of two carriageway lanes, followed by 10 tonne (I00kN) and 5 tonne (50 kN) vehicles. Design loads for short span members to allow for possible localconcentration of loads, the effect of two 90 kN wheel forces 0.90 m apart have been considered (i.e.approximately two 112 kN wheel forces with 25 % overstress).In general, normal loading is sufficient to cover 30 units of abnormal loading (Type HB) for loadedlengths above 30.0 m and for slabs (but see A.5), and at least 20 units of abnormal loading forbeams having spans less than 30.0 m carrying decks with a weight similar to that of an ordinaryreinforced concrete slab. Where a bridge is definitely required to carry abnormal loads in excess of20 units a check should be made.A special case is a narrow bridge or one in which the carriageway is cantilevered beyond the beams,where high stresses car.occur under abnormal loading.

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BS 153: Part 3A: 1972

A.4- Type HB loading

Type HB loading is a unit loading representing a single abnormally heavy vehicle.Figure 2 shows the plan and axle arrangementfor one unit this loading. The weight factora foreach of the four axles shall each be multipliedby an appropriate number of units.All parts of the btidge shall be capable of carry-ing Type HA loading, and shall be increased instrength, where necessary so as to be able tocarry Type HB loading as an alternative.

A.5 Application of type- HB loading.

A.5.1 No allowance for impact shall be made.:

A.5.2 t shah be permissible in considering theeffects of this loading to allow 25 % overstress(but see 4 in Part 38 for total permissiblestress).

A.5.3 The contact area of the heaviest wheelshall be taken as 375 mm x 75 mm the smallerdimension being taken in the direction oftravel.

A.5.4 Suitable provision shall be made for thedispersion (at 45 °} or distribution of the wheel loads where these can take place. .

A.5.5 Members which occur in such a positionthat they may be straddled by two axles orwheels of Type HB loading may, if desired, bedesigned by simple statical methods, subject toa reduction factor obtained from the followingtable where the bridge deck is designed to pos-sess sufficient rigidity to admit of reasonabletransverse distribution. The reduction can beapplied td jack arch decks.


BUKU PANDUAN REKABENTUK JAMBATANFOR INTERNAL USE ONLY

Spacing of member Reduction factor Spacing of members Reduction factor

mm

250500750

10001250

0.660.680.700.730.77

mm

1500175020002150

0.810.880.961.00

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C H A P T E R 4DECK. SLAB

DESIGN OF DECK SLAB

1.0 Introduction.2.0 Pigeaud’s Method:2.1 Application of Pigeaud's Method.3.0 Westergaard+s Method.3.1 Effect of encastre.3.2 Application of Westergaard's Method.

1.0 Introduction

In addition to the distribution of the load in themain longitudinal beams and the tranversediaphragm beam, there will also be a localstress distribution in the deck slab. Thislocal stress distribution is due to:

A) Dead load of deck slab and surfacing. B) HA Loading.C) HB wheel loads.

This stress distribution will, in general, berestricted to. the deck slab but may be superim-posed to give the resultant stress distribution inthe bridge as a whole.The boundary conditions of the deck slab arecomplex since the longitudinal and the tran-verse beams do not deflect equally. The prob-lem can be simplified by assuming.that theboundaries of the deck slab are simple andundeflecting. A factor is then introduced to takeaccount of,the continuity over the supports. Thedetermination of stress due to uniform loading,i.e dead load and HA load, is quite straight for-ward and methods described in CP 114 can beemployed. For stress due to wheel load, it maybe determined by Pigeaud's Method orWestergaard's Method. However, Westergaard's Method is the most commonly used since theconditions in most practical bridge structuresuit this method.

2.0 Pigeaud's Method

of the surfacing. Hence, for HB wheel ofdimension 15 in x 3 in.

u = 15+2tV = 3+ 2t

where t is the surfacing thickness.Ratio of a/b , u/a and v/b are.then calculated.Values of M1, and M2. can then be determinedfrom Pigeaud's Curve, where M.1 and M.2 .arefunctions of u/a and v/b for various values .ofP = a/b equal to 1.0. 0.9 , 0.8 , 0.707 , 0.6 , 0.50.4 , 0.3 , 0.2 and 0.The minimum moments are then derived asfollows:M= max. moment across direction a = ( M1 +0.15 M2) PM= max. moment across direction b = ( 0.15M1 + M 2) P .where P is,the wheel load in lbs and M and M2in lbs in/in. Pigeaud suggested that for two cen-tral load, as shown in figure 2, the value of Uand V should be taken as follows.


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2.1 Application of Pigeaud's Method.

Pigeaud's Method is most useful whdealing with slab in which the width is lessthan 1.8 times t e span. To take account offixity at the boundaries of the slab a factorof 0.8 is normally introduced. Thus themoments are derive for the simply supportedslab and multiplied by 0.8 to give the

approximate moment for the boundries.Some limitations of Pigeaud's Method are asfollows:

i)Only central load can be dealt with.

ii)When dealing with 2 loads, it is not sufficiently accurate to replacethe loads by a single load having an area which is dependant on the spacing.

iii) It is not very easy to read accurately the values of. MI and M2from Pigeaud's Curve.

3.0 Westergaard's MethodThe notation adopted by Westergaard is asshown.

The initial assumption is that the slab extendssufficiently far in the direction + y withoutbeing supported. by dia~ragms for it to be con-sidered as an infinite slab Poison's ratio wastaken as 0.15.


Fig.2. Notation in Pigeaud's Method for two central loads. u = 3 in + 2t } For load.as in fig.2 (a). v = w + bo + 2t }

and

u = w + bo + 2t } for load as in fig.2 (b)V = 3in + 2t }

Fig.3. Westergaard's Notation.

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REFERENCE'R.E. Rowe,, Concrete Bridge Design/Applied Science Publishers LTD

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C H A P T E R 5

BRIDGE BEARING, DOWEL BAR ANDEXPANSION JOINT

BEARINGS IN BRIDGES

1.0 DESIGN CODE (CONCERNINGELASTOMERIC BEARINGS)

Department of the Environment Highway Directorate Technical Memorandum (Bridges) No. BE 1/76

2.0 FUNCTIONS OF BEARINGS

i) To trgnsfer loads from superstructure to substructure.

ii) To accomodate expansion and contraction movements between different parts of a .structure.

iii)To accomodate q nd rotations of deck girders. Rotation occurs as the deck deflects under load.

iv)To limit the forces actually transmitted to the substructures by suitable design.

v) To damp down vibrations and minimise the effect of impact loading in case of elastomeric bearings.

3.0 SOURCES OF DISPLACEI%ENTS

3.1 Movement and rotations tend to occur in all types of structural members. In bridges, these are generated due to the following reasons:I) Temperature variationsii) Concrete shrinkage and creep iii) Effect of prestressingiv)Dead, superimposed and live loadsv) Tilt, settlements and seismic

disturbancesDisplacements can either be in the form ofmovement in the longitudinal, transverse andvertical directions, rotational modes or any oftheir combinations.3:2 For the purpose of,designing elastomericbearings, it is the practice of Unit Jambatan toconsider displacements only due to the

following factors:i) Longitudinal movements due to

temperature variation, creep and shrinkage of concrete (S.T.C effects).

ii) Rotation of girders due to the effect ofdead, superimposed and live loads.

4.0 TYPES OF BEARINGS

Basically, there are three different types of bearings commonly used in structural engineering. They are categorisedaccording to material

Classification as follows :i) Elastomeric Bearing.

An.elastomer is either vulcanised naturalrubber or synthetic material-calledneoprene having rubberlike characteristics. Movement and rotation are accommodated by compressing or shearing .the layers.

ii) Mechanical Bearing.The bearings are made up of metal such as steel. Movement and rotation are accommodated by rolling, rocking or sliding action of the metal parts.

iii) Combination of Elastomeric and Mechanical Parts..-For bearings in this category, elastomer is used as therotation medium'while horizontal movement capacity is.provided mechanically.


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5.0 INITIAL SELECTION OFBEARINGS

Many small bridges need no formal bearings. In general, this is true for spans below 10m, except where vibration is involved. In situation where bearings are required, they are designed and supplied bya specialist company. The criteria for the initial selection of bearings shall be based upon the following data :

6.0 ELASTOMERIC BEARING i

Basically all the bearings being designedand adopted by Unit Jambatan are of,theelastomeric type. This is so due to the fact that the majority of bridges are subjected to-loadings and rotations which are within the capacity ofelastomeric bearings.For the purpose of this design manual, only elastomeric bearing will be discussed.

6.1 PROPERTIES OF ELASTOMERElastomers can be produced with a widerange of physical properties. Some of the important properties include hardness, elastic, shear and bulk modulus which form part of the design parameters.


CHARACTERISTIC ELASTOMERIC MECHANICAL

Vertical load capacity (KN)Horizontal load capacity (KN)Horizontal movement (mm)

Rotatian about horizontal axis (rod)To resist uplist forcesVibration dampingMaintenanceContact stresses under bearing systemFirst costLife under proper maintenance schedule(years)

30002070

0.02improbable

possiblenegligible

lowerlower45-80

over 30,000over 3000Virtuallyunlimited

0.08possible

improbablerequiredhigherhigher

100-120

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The properties that formed the des4.gn parame-ters are as -tabulated below :

IRHD denotes International Rubber Hardnesswhose scale extends from 0 (very soft) to 100(very hard).

K is an empirically determined constant.

6.2 THREE TYPES OF ELASTOMERIC BEARINGS

i) A laminated bearing consists of one or more elastomer slabs bonded to metal plates so as to form a sandwich.

ii) A bearing pad is a singleunreinforced elastomer slab.

iii) A bearing strip is a continuous bearing pad for which B/L is greater than 5.

6.3 BASIC ASSUMPTIONS IN DESIGN

i) The elastomer is an elastic and almost incompressible material; its bulk modulus has to be taken into account where appropriate.

ii) There is no relative movement between elastomer andreinforcement plate at an interface.

iii) The thickness of bearing pads and strips shall be not less than 10mm nor greater than 25mm. (Not counting innerrubber slabs of laminated bearings).

iv)The thickness of the steel plate reinforcement shall be not less than 2(t1 + t2.,) V, but the thickness shall --------------A1.fsbe not less than 3mm for outer plates and not less than 1.5mm for internal plates. A greater thickness of


Hardness(IRHD)

Young’sModulus, E(N/mm2)

ShearModulusG (N/mm2)

KConstant

BuldModulus,E (N/mm2)

Elongationat Break,Xe (%)

4550556065

1.802.203.254.455.85

0.540.640.811.061.37

0.80.730.640.570.54

20002000200020002000

600600600450400

TABLE 1 (ELASTIC CONSTANT)

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ii) Rotational Capacity of bearing shall be equal to or greater than rotation of girderat support. An additional tolerance of 0.005 radian shall be added to the rotation of girders to cater for the seatingallowance.

iii) Factors on stability of bearing.iv) Friction location.This is to ascertain that

the bearing will not be displaced from the original position during service.

6.6 STATIC BEHAVIOUR OF ELASTOMER UNDER COMPRESSION

When a block of elastomer is loaded in compression, its vertical stiffeness depends upon its freedom to bulge at thesides. This is expressed in terms of the ‘shape factor’.

The shape factor depends on the dimensions ans shapes of the elastomer slab.The Vertical stiffeness of the block increases rapidly with the shape factor.

On the same plan area, a thinner block will be stiffer vertically.

ii) Partial Slippage.Under compressive loading, partial slippage will occur to the unbonded layers of an elastomeric bearing. Thus, the vertical stiffeness of the unbonded layersare reduced.To compensate for this, the two outer layers of a laminated bearing is treated as being 40% greater than the actual thickness. For the inner layers, since they are bonded on both sides by the steel plates, the effective thickness is equal to the actual thickness. For pad and strip bearings, their thickness is treated as being 80% greater than the actual thickness


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7.0 LOCATION OF BEARING BYFRICTION

When a bearing is subjected to direct shear strain, horizontal force is induced which tends to displace the bearing from its original position. To prevent this happening, there must be sufficient minimum vertical load acting on the bearing. Assuming the coefficient of friction between elastomer and concreteseating of 0.33 and a coefficient of 0.25 with steel seating, the friction location ischecked as follow :

7.1 DESIGN EXAMPLE

The bridge designer can either select proprietory elastomeric bearings, or design bearings in detail, or even simplyspecify the requisite loads, movements and rotations, and then approve the bearing details submitted by the contractor. Standard. proprietory bearings, even if not fully loaded, will prove to be cheaper than special designs.The design of elastomeric bearings is essentially a trial and error process.The plan size of a bearing is normally governed by the. width of the beam it supports and the width of the abutment seating in the direction of the bridge span.

An elastomeric bearing shall now be designed to satisfy the following requirements:-

NoteThe rotation of the beam shall include an additional tolerance of 0.005 radians to.caterfor the seating allowgnce. Thus, the minimumrotational capacity of the bearing shall.be 0.006and 0.008 radians respectively under HA andHB loadings.


Minimum Compressive Force, V min.----------------------------------------------- > 3 for elastomer in contactMaximum Horizontal Force, H max with concrete

(> 4 for steel contact)V min = Dead Load AloneH Max = Ao G e b

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The carrying capacity of a free P nd bearing,subjected to horizontal movement, can be takento be about 0.8 S N/mm2, as a first guess.Normally,, laminating is required in order toprovide sufficient horizontal movement, whilemaintaining the vertical load carrying capacity.Plain.pad.may be sufficient if horizontal movement is very small, but not in this case.Horizontal movement of about half the totalthickness of elastomer can be used as a startingpoint in design.


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DESIGN OF DOWEL BARS

1) Elastomeric bearing can he conveniently subdivided into two types 'fixed', where the support member can only rotate, all horizontal movements. being restrained, and 'free', where the member can rctate and also move horizontally.

2) The fixed state is provided by dowelspassing from the beam. to its support. In order to make provision for the possible replacement of bearings, these dowels are best placed between bearings, but where space is restricted they car. pass through holes in the bearing. Dowels usually need anelastomeric cap at one end to permit the superstructure to rotate relative to the substructure. The dowels must penetrate to sufficient depth to resist the horizontal load, without inducing excessive stresses in the concrete. In all cases the doi,lels should be long enough to reach the main reinforcementin the support.

3) Dowel bars at one end of a bridge span will form an expansion centre line, longitudinal movements of the deck will be accomodatedby the bearings at the free end, horizontal loads will be carried by the dowels.It should be remembered that horizontal forces will be transmitted to the support at the tree end, due to the resistance of the bearings there to the horizontal movements, and this same force will be transmitted through the superstructure to the fixed end dowels. In Unit Jambatan,this force is calculated on the basis of the movement of the deck due /to changes in temperature, shrinkage and creep of concrete ( S.T.C ).

4) The dowel bars shall be designed to resist a combination of three types of horizontal loadas follows:(i) Tractive load(ii) Wind load. (iii)Load due to the effect of S.T.C above.

(Note: The load due to S.T.C is such that F- ZA,G eb,)

5) TYPICAL CALCULATION

A) Design suibtable dowel bars at the fixed end of a bridge span to transfer the horizontal forces to the abutment. Input datas are as follwos :


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EXPANSION JOINTS

1) GENERALThe expansion joint is an integral part of anybridge structure and should be considered atan early stage in the design. Joints which are properly designed, installed by specialistoperatives together with reasonable maintenance should give trouble freeservice within its lifespan. Expansion joint is situated in the most vulnerable position on the bridge deck where it is subjected to impact.loading, vibration and exposed to dirt, ozone attack and other corrosive chemicals.

2) FUNCTIONAL REQUIREMENTS . These are as follows

i) To accommodate movements and withstand loadings.

ii) To cater for operational needs.

The sources of movements to be accommodated by an expansion joint are identical to that of a bearing.For this reason, expansion joints and bearings of anyparticular span of a bridge shall be designed to be compatible. An expansion joint shall be designed to withstand a combination of vertical and horizontal loads. This shall be discussed later under the heading of design load.

The operational requirements for joints are as follows i)Possess good riding characteristics.ii) Not a skid hazard or danger.iii) Silent and vibration freeiv) Be sealed against1water and foreign

matter or make provision for their disposal.

v) Be capable of absorbing the various typesand ranges of movement., without being extruded or expelled from position.

vi) Riding surface of joint must be able to withstand wear and tear and be durable against petroleum product, weather, etc.

vii) Facilities easy inspection, maintenance and repair

4) CLASSIFICATION OF EXPANSION JOINTS.

i) Open Gap Joint.The joint comprises of two edges which are spaced some distance apart and not interconnected by. any load supporting connection. There are two categories of open gap joint :

a) Buried joint under continuous premix surfacing. Most of the expansion joints being adopted by Unit Jambatan fall under this category.

b)Exposed joints which are installed to flush with the wearing surface ofthe bridge deck. The joint may becompletely opened or be sealed up with,say, neoprene sealing element.

ii) Covered Gap Joint ( or Bridged Joint ).The gap is bridged by a sliding plate or some other transverse structural element.The structural element will be subjected to a combination of vertical and horizontal loads.

iii) Composite Expansion Joint.The joint comprises of a gap bridging element for carrying the traffic loads together with a deformable closing seal element to ensure continuity of the carriageway surface.


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5) SELECTION OF JOINT TYPEThis is largely determined by the total range.of movement to be expected.

6) DESIGN CONSIDERATIONS .Expansion gap should be straight of uniform width and have a minimum gap of6mm at maximum temperature.

7) DESIGN LOADa) Vertical Two 112 KN wheel loads, 0.9m

apart, with a contact area of 265 x 265mm. It shall be applied to the edge ef.the expansion gap. It.may be spread tranversely over such a length as isjustified by the continuity and rigidity ofthe joint subject to a maximum of 450mm on either side of the centre line of each wheel.

b) HorizontalA traffic force of 60KN/m run o£ joint, acting at load level..

8) ANCHORAGE SYSTEMi) The joints are severely loaded. Forces

involved are vertical, horizontal togetherwith twisting moments.

ii) The common types of anchorage system: .- Epoxy mortar nosing.- Anchor bars.- Holding down bolts ( May be prestressed ).

iii) Stresses in concrete, structural steel, epoxy mortar etc must be within the permissible values.

9) INSTALLATION OF EXPANSION JOINTi) The whole operation shall receive

competent supervision. Only.proper materials and equipment shall be used, in accordancewith the manufacturersinstructions.

ii) Prior to installing the joint system, the bedding shall be prepared accordingly without traces of dirt, oil and other impurities.

iii) Composite meoprene expansion

joints are installed in precompressed condition:- During placing+fconcrete or epoxymortar, the joint assembly shall be immovable both in vertical and horizontaldirections.

- Can be achieved by :-a) Clamp down the joint assembly.b) Install under uniform temperature

condition.iv) The joint shall hot be subjected to any

kind of loading until /all the materials have gained the required strength.

10) PROVISION FOR DRAINAGEWater and other foreign products shall not be allowed to reach the bearings, girders, pier head etc, Provision must be made to prevent the ingress of surface water through the joint.i) For water tight joints, ensure that the

sealing agents are performing in the manner intended.

ii) For large open joints, Special drainage techniques must be adopted to deal with surface water, earth etc, easy access for cleaning shall be provided.

iii) Provide with proper Camber and crossfall within the carriageway surface around the joint to discharge water.

v) Water that collects and runs along thekerbs sould be intercepted by suitable drainage outlet before it reaches the joints

11) MAINTENANCEIt is essential that expansion joints are easily accessible for the purpose of maintenance.

i) Joints shall be regularly inspected to ensure that no parts are loose, thesealing materials are intact, and drainagesystems are working properly.

ii) Safeguard the screws and bolts against corrosion. Holding down bolts need to be retentioned to the required torque once they are.loose.


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iii) Ensure that no debris are left to accumulate in the joint gape This will induce enormous restraining forces causing damaging effects.

iv) The road surface should be maintained to the level of the joint and in no case should the difference in level become more than 6mm.

References.

1. Department of the Environment Highways Directorate. Technical Memorandum B.E. 1/76.Design Requirements For Elastomeric Bridge Bearings.

2. Bearings in Structural Engineering.J.E. Long M. Sc. M.I.C.E., M.I. Structural Engineering. Newnes - Butterworths, London. (1974)

3. The Theory and Practice of Bearings and Expansion Joints For Bridges. David J. LeeB. Sc. Tech, DIC, C. Eng., FILE, FI Struct. E.Cement & }Concrete Association (1971)

4. Expansion Joints in Bridges and Concrete Roads. - W. Koster.Maclaren & Sons, London..

5. Department of the Environment HighwaysDirectorate. Technical Memorandum BE 3/72.Design Requirement for Expansion Joints.


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