002 -preliminary sections

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Bridge Design Manual - 2002 Preface

Ethiopian Roads Authority Page i

PREFACE

This Bridge Design Manual-2002 is one of the series of Design Manuals, Standard ContractDocuments and Specifications prepared under a credit financing of the International

Development Agency (IDA). The consulting services were provided by the Louis Berger

Group, Inc.

This manual has been developed from current international practice appropriately modified

to take account of local experience and conditions. It is written for the practicing Engineer.

ERA formed a Working Group charged with evaluating and commenting upon the draft

manual and guiding the Consultant on the preparation of the final manuals. Members of the

Working Group and the Louis Berger Group/SABA team for this manual consists of thefollowing:

1. Ato Fesseha Taffese

A/Manager, Design, Research and Network Management Division - Group Chairman2. Ato Fekadu Haile

Senior Advisor to the General Manager- Group Secretary

3. Mr. Peter DrummondRoad Sector Development Programme Advisor to the General Manager

4. Mr. Brian S. Barr

Rural Roads Coordinator5. Ato Yemane Shiferaw

Head, Design and Research Branch

6. Ato Girma WorkuHead, Bridges & Structure Branch

7. Ato Yohanese Bantyederu

Engineer from the Design Branch

Mr. Michael S. Nyquist - Louis Berger Group Project Manager

Mr. Lennart Rahm - Louis Berger Group Structural Engineer

Mr. Henok Aberra - SABA PLC Structural Engineer

Companion Documents and Manuals prepared under the same service are the following:

1. Geometric Design Manual-20022. Site Investigation Manual-2002

3. Pavement Design Manual Volume I-2002 (Flexible & Gravel)4. Pavement Design Manual Volume II-2002 (Rigid Pavements)5. Overlay/Rehabilitation Manual-2002

6. Drainage Design Manual -2002

7. Standard Environmental Procedures Manual-2002

8. Standard Detail Drawings-20029. Standard Technical Specifications - 2002


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Preface Bridge Design Manual - 2002

Page ii Ethiopian Roads Authority

10. Standard Tendering Documents For Road Work Contracts National Competitive

Tendering (NCT) - 2002

11. Standard Bidding Documents For Road Work ContractsInternational Competitive Bidding (ICB) - 2002

Appropriate reviews and comments were also provided by agencies and individuals throughERAs Project Working Group. The Working Group wishes to acknowledge for the

contributions made by all other specialists within ERA and outside of ERA in thepreparation of these Manuals and Documents.

The layout of this Manual has been arranged with the following hierarchy:

Chapter Major heading or Section (level one)

Sub-Section within the major heading (level two)

Sub-sub-Section within the second level subject matter (level three)

All tables are described by number beginning with one (1) at the first of each Chapter.Figures are described in a similar manner.

Updates:

This manual will be updated and revised from time to time, as deemed appropriate.

Significant changes to criteria, procedures or any other relevant issues related to the newpolicies or revised law of the land, ERA, or that is mandated by the relevant Federal

Government Ministry or Agency, should be amended and incorporated in the manual as soon

as possible after their date of effectiveness.

Other minor changes, not affecting the whole nature of this manual, may be accumulated and

made periodically. When a change is approved, new page(s) instituting the revisions,together with the revision date, will be issued and inserted in to the relevant Chapters.

All revisions to the Bridge Design Manual will be made strictly in accordance with the

following procedures:

(1) Any proposed change will be submitted by or through the Head of the Design

(Branch, Division) of ERA.

(2) The proposed change, addition, or deletion will be submitted on a Manual Change

form 1-1(see the attached form) and forwarded with an explanation of its need and

purpose.

(3) If the change is approved, the General Manager will sign the Manual Change form

and return a copy to the Head of the Design (Branch, Division), who will arrange for

the change to be incorporated into the Bridge Design Manual.

(4) The Head of the Design (Branch, Division) will re-issue all effected pages of the

manual showing the proper revision date as shown on the Manual Change form.1-1.


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Bridge Design Manual - 2002 Preface

Ethiopian Roads Authority Page iii

ETHIOPIAN ROADS AUTHORITY

BRIDGEDESIGNMANUAL

This area to be competed by the

Head of ERA Design (Branch ,

Division)

MANUAL CHANGE CHANGE NO._____________(SECTION NO. CHANGE NO.

_____________-

____________

Section

Table

Figure

Explanation To be deleted To be inserted

Submitted by: __________________ Approved by: ____________________________

Head of Design (Branch, Divisio ERA General Manager

Date: ___________________ Date: ___________________

Manual change Form 1-1


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Foreword Bridge Design Manual - 2002

Page iv Ethiopian Roads Authority

FOREWORD

This is the first comprehensive Bridge Design Manual prepared for the use and technicalguidance of design personnel of the Ethiopian Roads Authority and consultants doing Bridge

Design for the Authority. However, it may also be used as a guide by other agencies

undertaking relevant work in the road sector.

The Ethiopian Roads Authority has prepared this Manual under a credit from the

International Development Agency (IDA) for design of roads in order to standardize design

practices in all ERA design works.

The road network comprises a huge national asset that requires adherence to appropriate

standards for design, construction and maintenance in order to provide a high level of

service. As the length of the engineered road network is increasing, appropriate choice ofmethods to preserve this investment becomes increasingly important.

This Manual has particular reference to the prevailing conditions in Ethiopia and reflects

ERAs experience gained through activities within the road sector during the last 50 years.

The design standards set out in this Manual shall be adhered to unless otherwise directed by

the concerned bodies with in ERA. However, I will like to emphasize that careful

consideration to sound engineering practice shall be observed in the use of the Manual, andunder no circumstances shall the Manual waive professional judgment in applied

engineering. For simplification in reference this Manual may be cited as ERA Bridge

Design Manual - 2002.

It is my sincere hope that this Manual will provide all users with both a standard reference

and a ready source of good practice for the design of roads, and will assist in a cost effective

operation, and environmentally sustainable development of our road network.

I look forward to the practices contained in this Manual being quickly adopted into our

operations, thereby making a sustainable contribution to the improved infrastructure of our

country.

As this Manual due to Technological development and change, requires periodic updating,

comments and suggestions on all aspects from any concerned body, group or individual as

feedback during its implementation is expected and will be highly appreciated.

Tesfamichael Nahusenay

General Manager

ETHIOPIAN ROADS AUTHORITY


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Bridge Design Manual - 2002 Acknowledgements

Ethiopian Roads Authority Page v

ACKNOWLEDGEMENTS

This Bridge Design Manual - 2002 is based on a review of the design standards of several

countries, among which are AASHTO, ITE, FHA and TRB (USA), TRRL (UK), EBCS

(Ethiopia), Swedish standards, Australian Standards and EUROCODE 1,2,3 (Europe).

In the selection of the appropriate bridge standards for Ethiopia, material from these and

other sources have been gleaned and evaluated to determine the set of standards mostappropriate for Ethiopia and Ethiopian conditions.

The authors of the manual are listed in the preface.


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Bridge Design Manual - 2002 Table of Contents

Ethiopian Roads Authority Page vii

TABLE OF CONTENTS

Preface... .....................................................................................................................................i

Foreword...................................................................................................................................ivAcknowledgements....................................................................................................................vList of Illustrations ................................................................................................................. xii

Glossary ... ..............................................................................................................................xix

Abbreviations .......................................................................................................................xxvi

1 Introduction

1.1 Units..................................................................................................................... 1-2

1.2 Conversion Factors: (Metric to/from SI-units) .................................................... 1-2

2 General Requirements

2.1 Design Philosophy............................................................................................... 2-12.2 Notations.............................................................................................................. 2-12.3 Geometric Requirements ..................................................................................... 2-2

2.4 Minimum Dimensions ......................................................................................... 2-4

2.5 Load Assumptions ............................................................................................... 2-82.6 Deflection .......................................................................................................... 2-10

2.7 Design Working Life ......................................................................................... 2-11

2.8 Limit States........................................................................................................ 2-112.9 Ductility............................................................................................................. 2-13

2.10 Redundancy ....................................................................................................... 2-14

3 Load Requirements3.1 Scope.................................................................................................................... 3-1

3.2 Notations.............................................................................................................. 3-1

3.3 Load Factors and Combinations .......................................................................... 3-43.4 Load Factors for Construction Loads .................................................................. 3-9

3.5 Load Factors for Jacking and Posttensioning Forces .......................................... 3-9

3.6 Dead Loads (DC = Structural Component; DW = Wearing Surface;

EV = Vertical Earthfill) ....................................................................................... 3-93.7 Earth Loads (EH = Horizontal Earth; ES = Earth Surcharge;

DD = Downdrag) ............................................................................................... 3-10

3.8 Gravity Loads: (LL = Vehicular Live Load; PL = Pedestrian Live Load) ........ 3-103.9 Application of Design Vehicular Live Loads.................................................... 3-17

3.10 Fatigue Load ...................................................................................................... 3-19

3.11 Rail Transit Load ............................................................................................... 3-223.12 Pedestrian Loads................................................................................................ 3-22

3.13 Dynamic Load Allowance (IM = Vehicular Dynamic Load Allowance) ......... 3-23

3.14 Centrifugal Forces (CE = Vehicular Centrifugal Force) ................................... 3-24

3.15 Braking Force (BR = Vehicular Braking Force) ............................................... 3-253.16 Vehicular Collision Force (CT = Vehicular Collision Force) ........................... 3-25

3.17 Water Loads (WA = Water Load and Stream Pressure) .................................... 3-26


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3.18 Wind Load (WL = Wind on Live Load; WS = Wind Load on Structure)..........3-29

3.19 Earthquake Effects (EQ = Earthquake).............................................................. 3-34

3.20 Earth Pressure (EH = Horizontal Earth Pressure; ES = Earth Surcharge;Ls = Live Load Surcharge; DD = Downdrag)....................................................3-50

3.21 Force Effects Due to Superimposed Deformations: TU, TG, SH, CR, SE........3-68

3.22 Friction Forces: FR............................................................................................. 3-70

4 Planning Stage/Feasibility Study/Site Investigation

4.1 General ................................................................................................................. 4-1

4.2 Site Selection........................................................................................................4-14.3 Site Conditions .....................................................................................................4-3

4.4 Cross-Section of River (see ERA Drainage Design Manual-2002, ERA Site

Investigation Manual-2002...................................................................................4-44.5 Proposed Typical Section of Road .......................................................................4-4

4.6 Sketch of Proposed Bridge and Brief Technical Descriptions of Bridges ...........4-4

4.7 Existing Bridges ................................................................................................... 4-5

4.8 Cost/Benefit Analysis and Evaluation..................................................................4-54.9 Site Investigation..................................................................................................4-5

5 Preliminary Design/Layout of Bridges and Culverts

5.1 General ................................................................................................................. 5-15.2 Basic Information ................................................................................................. 5-1

5.3 Geometric Requirements......................................................................................5-4

5.4 Load Assumptions................................................................................................ 5-45.5 Foundations ..........................................................................................................5-4

5.6 Scour/Erosion, Riprap, River Training, Etc. ........................................................ 5-7

5.7 Substructure/Abutments, Piers, Wingwalls, and Retaining Walls .......................5-95.8 Low Level Water Crossings ............................................................................... 5.11

5.9 Frame Bridge......................................................................................................5-14

5.10 Slab Bridge......................................................................................................... 5-16

5.11 Girder Bridge......................................................................................................5-175.12 Masonry and Concrete Arch Bridges .................................................................5-19

5.13 Prefabricated Bridges .........................................................................................5-20

5.14 Pedestrian Footbridges .......................................................................................5-235.15 Cattle Underpasses .............................................................................................5-23

5.16 Other Types of Bridges (Cablestay, Suspension, Truss, Railway) ....................5-23

5.17 Temporary Bridges.............................................................................................5-245.18 Backwater...........................................................................................................5-29

5.19 Selection of Bridge Type....................................................................................5-29

5.20 Railings and Parapets .........................................................................................5-315.21 Checklist for the Preliminary Design Drawing(s)..............................................5-315.22 Checklist for the Preliminary Design Standards (PDS) .....................................5-33

5.23 Sample Preliminary Design Specifications ........................................................ 5-35

6 Substructure Design6.1 Scope......................................................................................................................6-1

6.2 Notation .................................................................................................................6-1


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Ethiopian Roads Authority Page ix

6.3 Foundations ........................................................................................................... 6-2

6.4 Pier Design.......................................................................................................... 6-10

6.5 Abutments ........................................................................................................... 6-106.6 Wingwall and Retaining Wall Design................................................................. 6-11

6.7 Culverts and Other Buried Structures ................................................................. 6-12

7 Superstructure Design7.1 Scope ..................................................................................................................... 7-17.2 Notations ............................................................................................................... 7-1

7.3 General .................................................................................................................. 7-2

7.4 Slabs ...................................................................................................................... 7-67.5 Girders (Concrete, Steel, Composite Bridges)...................................................... 7-9

7.6 Trusses (Steel)..................................................................................................... 7-12

7.7 Arch Bridges and Stone Masonry Piers .............................................................. 7-12

8 Bridge Details8.1 Scope ..................................................................................................................... 8-1

8.2 Notation................................................................................................................. 8-18.3 Bearings................................................................................................................. 8-28.4 Expansion Joints.................................................................................................. 8-18

8.5 Railings ............................................................................................................... 8-19

8.6 Drainage of Bridge Decks................................................................................... 8-208.7 Utilities (Service Ducts, Cables, Etc.)................................................................. 8-20

9 Reinforced Concrete

9.1 Scope ..................................................................................................................... 9-1

9.2 Notation................................................................................................................. 9-19.3 Concrete ................................................................................................................ 9-3

9.4 Reinforcement ....................................................................................................... 9-69.5 Prestressing Steel/Post-Tensioning Steel ............................................................ 9-169.6 Limit States ......................................................................................................... 9-16

9.7 Shear and Torsion Design ................................................................................... 9-17

9.8 Deformations....................................................................................................... 9-189.9 Compression Members........................................................................................ 9-19

10 Structural Steel10.1 Scope................................................................................................................. 10-1

10.2 Structural Steels ................................................................................................ 10-110.3 Steel Design Details.......................................................................................... 10-2

11 Other Structural Materials11.1 Scope................................................................................................................. 11-111.2 Notation ............................................................................................................ 11-1

11.3 Requirements for Timber.................................................................................. 11-1

11.4 Requirements for Stone .................................................................................... 11-5

12 Detail Design of Bridges and Structures

12.1 General.............................................................................................................. 12-1


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12.2 Notations ......................................................................................................... 12-1

12.3 Seismic Design Methods.................................................................................12-4

12.4 Foundations .....................................................................................................12-512.5 Retaining Walls .............................................................................................12-13

12.6 Culverts ......................................................................................................... 12-14

12.7 Substructures for RC Bridges........................................................................12-1812.8 Superstructure for RC Bridges ......................................................................12-28

12.9 Frame Bridges ...............................................................................................12-42

12.10 Precast Concrete Bridges............................................................................... 12-4412.11 Arch Bridges (Masonry and Concrete) ......................................................... 12-44

12.12 Composite Steel/Concrete Bridge .................................................................12-48

12.13 Timber Bridges.............................................................................................. 12-49

12.14 Other Types of Bridges .................................................................................12-5112.15 Bearing Design.............................................................................................. 12-53

12.16 Software for Bridge Design...........................................................................12-55

13 Approximate Methods of Analysis13.1 General .............................................................................................................. 13-1

13.2 Notation ............................................................................................................. 13-1

13.3 Decks ................................................................................................................. 13-313.4 Beam-Slab Bridges............................................................................................13-8

13.5 Equivalent Strip Widths for Slab-Type Bridges..............................................13-18

13.6 Equivalent Length Factor, K ...........................................................................13-1913.7 Shear-Sectional Design Model ........................................................................13-19

14 Strength Evaluation of Existing Steel, Concrete and Masonry Arch Bridges

14.1 Introduction ....................................................................................................... 14-114.2 Notations............................................................................................................14-2

14.3 Strength Evaluation of Bridges .........................................................................14-3

14.4 Numerical Examples .......................................................................................14-22

14.5 Masonry Arch Bridge Rating ..........................................................................14-24

15 The Quality System ISO 9000

15.1 General .............................................................................................................. 15-1

15.2 Background of the Existing Quality System Standard ISO 9000......................15-415.3 Information Publications on Quality System .................................................... 15-7

16 Calculations, Drawings and Specifications

16.1 Format of Calculations, Drawings and Specifications ......................................16-1

16.2 Quality Control of Calculations and Drawings .................................................16-4


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Ethiopian Roads Authority Page xi

APPENDICES

CB Composite Bridge 24.0-m span, 7.32-m width ................................................CB1-CB63

EB Steel Reinforced Elastic Bearings ...................................................................... EB1-EB3

GB Girder Bridge................................................................................................... GB1-GB28

MB Masonry Bridge 12.0-m span & 7.32-m width .............................................. MB1-MB37

RB Roller Bearings...................................................................................................RB1-RB2

RW Design of RC Cantilever Retaining Wall...................................................... RW1-RW12

SB Slab Bridge 6.0-m clear span & 4.5-m width....................................................SB1-SB10

TB Timber Bridge 12.0-m span & 4.5-m width....................................................... TB1-TB5


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List of Illustrations Bridge Design Manual - 2002

Page xii Ethiopian Roads Authority

LIST OF ILLUSTRATIONS

Figures

Figure 2-1 Definition of Bridge Dimensions ................................................................. 2-2

Figure 3-1 Moment and Shear Ratios: Exclusion Vehicles to HS20 (truck or lane)

or Two 110 kN Axles at 1.2m .....................................................................3-13Figure 3-2 Moment and Shear Ratios: Exclusion Vehicles to National Model ...........3-14

Figure 3-3 Moment and Shear Ratios: Notional Model to HS20 (truck or lane) or

Two 110 kN Axles at 1.2m..........................................................................3-14Figure 3-4 Characteristics of the Design Truck ............................................................3-15

Figure 3-5 Design Tandem Load...................................................................................3-16

Figure 3-6 Debris Raft for Pier Design .........................................................................3-28

Figure 3-7 Plan View of Pier Showing Stream Flow Pressure .....................................3-28Figure 3-8 Flow Chart for Seismic Design of Bridge Components ..............................3-36

Figure 3-9 Earthquake Zones ........................................................................................3-37

Figure 3-10 Seismic Response Coefficients, CSM for Various Soil Profiles,Normalized with Respect to Acceleration Coefficient A

(CSM on the left axis)...................................................................................3-39

Figure 3-11 Hold down device ........................................................................................3-44Figure 3-12 Longitudinal loading....................................................................................3-46

Figure 3-13 Effect of Groundwater Table .......................................................................3-52

Figure 3-14 Location of Resultant for Horizontal Earth Pressure...................................3-53Figure 3-15 Notation for Coulomb at Earth Pressure......................................................3-55

Figure 3-16 Application of Coulomb Earth Pressure Theories in Retaining

Wall Design .................................................................................................3-56

Figure 3-17 Computational Procedures for Passive Earth Pressures for SlopingWall with Horizontal Backfill .....................................................................3-57

Figure 3-18 Computational Procedures for Passive Earth Pressures for Vertical

Wall with Sloping Backfill ..........................................................................3-58Figure 3-19 Settlement Profiles Behind Braced or Anchored Walls ..............................3-61

Figure 3-20 Earth Pressure Distribution for MSE Wall with Level Backfill Surface.....3-62

Figure 3-21 Earth Pressure Distribution for MSE Wall with Sloping Backfill Surface .3-62Figure 3-22 Earth Pressure Distribution for MSE Wall with Broken Back

Backfill Surface ...........................................................................................3-63

Figure 3-23 Horizontal Pressure on Wall Caused by Uniformly Loaded Strip ..............3-64

Figure 3-24 Horizontal Pressure on Wall Caused by a Point Load.................................3-64

Figure 3-25 Horizontal Pressure on Wall Caused by an Infinitely Long LineLoad Parallel to the Wall ............................................................................3-65

Figure 3-26 Horizontal Pressure on Wall Caused by a Finite Line LoadPerpendicular to the Wall ............................................................................3-66

Figure 3-27 Positive Vertical Temperature Gradient in Concrete and Steel

Superstructures ............................................................................................3-69

Figure 4-1 Sketch of Bridge Site.....................................................................................4-9


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Figure 5-1 Compacted Fill Under a Bridge Footing.......................................................5-6

Figure 5-2 Two Types of Abutments..............................................................................5-9

Figure 5-3 Typical Parallel and 45 Wingwalls Attached to the Abutment .................. 5-10Figure 5-4 Typical Combined Attached Wingwall and Retaining Wall ....................... 5-11

Figure 5-5 Bed Level Causeways, Common Types ...................................................... 5-13

Figure 5-6 Design Heights of Open Single Span Frame Bridges.................................. 5-15Figure 5-7 Requirements for Skewed Frame Bridges ................................................... 5-16Figure 5-8 Sections of Voided (Hollowed) Slab and Ribbed Slab Bridges................... 5-16

Figure 5-9 Typical Elevated Footing with Endwalls..................................................... 5-17

Figure 5-10 Cross-Reinforced Hinge............................................................................... 5-20Figure 5-11 Section of a Typical Slab Panel ................................................................... 5-21

Figure 5-12 Section of U-Shaped Type of RC Girder Panels.......................................... 5-21

Figure 5-13 Section of a Normal T-Shaped Type of Stressed RC Girder Panel ............. 5-22Figure 5-14 Section of Stressed I-Shaped Type of RC Girder Panels............................. 5-22

Figure 5-15 Section of I-Shaped Type of RC Girder Panel Bridge for Pedestrians ........ 5-22

Figure 5-16 Typical Sections of Railway Bridges and their Suitable Span Lengths....... 5-25

Figure 5-17 Temporary Bridge on Gabion Abutments.................................................... 5-27Figure 5-18 Bridge Pier Made of Concrete Rings ................................................................................... 5-28

Figure 5-19 Skewed (Bottom) and Perpendicular (Top) Bridge.............................................................. 5-30

Figure 5-20 Preliminary Design Drawing................................................................................................ 5-36

Figure 6-1 Procedure for Estimating Sliding Resistance for Walls on Clay ................... 6-6

Figure 7-1 Free Body Diagrams ...................................................................................... 7-4

Figure 7-2 Reinforcement Layout.................................................................................... 7-7

Figure 7-3 Definition of the Parameter Xu..................................................................... 7-10

Figure 8-1 Steel Roller Bearing ....................................................................................... 8-2

Figure 8-2 Reinforced Elastomeric Bearing .................................................................... 8-3Figure 8-3 Determination of A2 for a Stepped Support ................................................... 8-5Figure 8-4 Stress-Strain Curves ..................................................................................... 8-13

Figure 8-5 Elastomeric Bearing-Interaction between Compressive

Stress and Rotation Angle............................................................................ 8-15Figure 8-6 Principle for Multi-Panel Expansion Joint................................................... 8-19

Figure 9-1 Factor kc for Volume to Surface Ratio .......................................................... 9-5

Figure 12-1 Reduced Footings Dimensions .................................................................... 12-5

Figure 12-2 Example of Critical Sections for Shear in Footings .................................... 12-8

Figure 12-3 Coefficient Cd for Trench Installations ...................................................... 12-17Figure 12-4 Factor ks for Volume-to-Surface Ratio...................................................... 12-19

Figure 12-5 Active Wedge Force Diagram ................................................................... 12-28

Figure 12-6 Recommended Arch Shape........................................................................ 12-45Figure 12-7 Common Bearing Types ............................................................................ 12-55

Figure 13-1 Notional Model for Applying Lever Rule to Three-Girder Bridges............ 13-8Figure 13-2 Common Deck Superstructures ................................................................. 13-12


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Page xiv Ethiopian Roads Authority

Figure 13-3 Values of and for Sections with Transverse Reinforcement................13-21Figure 13-4 Values of and for Sections without Transverse Reinforcement...........13-22Figure 13-5 Illustration of Ac .........................................................................................13-24

Figure 13-6 Flow Chart for Shear Design......................................................................13-25Figure 13-7 Guide to the Selection of Sx .......................................................................13-26

Figure 13-8 Forces Assumed in Resistance Model Caused by Moment and Shear.......13-27

Figure 14-1 Flow Chart for Rating Procedure .................................................................14-8

Figure 14-2 Truck Type 3 Unit Weight = 227 kN .........................................................14-11

Figure 14-3 Truck Type 3-2 Unit Weight = 325 kN......................................................14-12Figure 14-4 Truck Type 3-3 Unit Weight = 364 kN......................................................14-12

Figure 14-5 The Legal Lane Loading (mainly for large spans) .....................................14-12

Figure 14-6 Flow Chart for Selecting Resistance Factors ..........................................14-19Figure 14-7 Nomogram for Determining the Provisional Axle

Loading of Masonry Arch Bridges before Factoring ................................14-27

Figure 14-8 Arch Dimensions .......................................................................................14-28

Figure 14-9 Span/Rise Factor ........................................................................................14-29Figure 14-10 Profile Factor .............................................................................................14-30

Figure 14-11 Conversion of Modified Axle Loads to Single Double and Triple Axles .14-35

Figure 14-12 Spandrel Wall Failures ..............................................................................14-39


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Ethiopian Roads Authority Page xv

Tables

Table 2-1 Minimum Dimensions ...................................................................................... 2-4Table 2-2 Table of Bridge Widths ................................................................................... 2-5

Table 2-3 Vertical Clearance at Design Flood Level (DFL)............................................. 2-6

Table 2-4 Maximum Allowable Slope Grade for Different Slope Materials ................... 2-7

Table 3-1 Limit States....................................................................................................... 3-4

Table 3-2 Load Combinations and Load Factors.............................................................. 3-6

Table 3-3 Load Factors for Permanent Loads, p .............................................................. 3-7Table 3-4 Densities and Force Effects of Different Materials ........................................ 3-10Table 3-5 Multiple Presence Factors m....................................................................... 3-11

Table 3-6 Fraction of Truck Traffic in a Single Lane, P................................................. 3-20

Table 3-7 Fraction of Trucks in Traffic .......................................................................... 3-20Table 3-8 Dynamic Load Allowance, IM ....................................................................... 3-23

Table 3-9 Drag Coefficient ............................................................................................. 3-27

Table 3-10 Lateral Drag Coefficient ................................................................................. 3-28Table 3-11 Values of Vo and Zo for Various Upstream Surface Conditions .................... 3-30

Table 3-12 Base Pressures, PB Corresponding to VB = 160 km/h (45 m/s)...................... 3-31

Table 3-13 Base Wind Pressures, PB (kPa) for Various Angles ofAttack VB = 160 km/h..................................................................................... 3-31

Table 3-14 Wind Components on Live Load.................................................................... 3-32

Table 3-15 Seismic Zones................................................................................................. 3-37

Table 3-16 Site Coefficients.............................................................................................. 3-38Table 3-17 Response Modification R-Factors for Substructures...................................... 3-40

Table 3-18 Response Modification R-Factors for Connections........................................ 3-41

Table 3-19 Minimum Analysis Requirements for Seismic Effects .................................. 3-45

Table 3-20 Regular Bridge Requirements......................................................................... 3-46Table 3-21 Approximate Values of Relative Movements Required to

Reach Minimum Active or Maximum Passive Earth Pressure Conditions.... 3-50Table 3-22 Typical Coefficients of Lateral Earth Pressure At-Rest (ko) .......................... 3-54

Table 3-23 Friction Angle for Dissimilar Materials ......................................................... 3-55

Table 3-24 Typical Values for Equivalent-Fluid Densities of Soils ................................. 3-59

Table 3-25 Equivalent Height of Soil, heq for Different Wall HeightsDue to Vehicular Loading .............................................................................. 3-67

Table 3-26 Temperature Ranges ....................................................................................... 3-68

Table 3-27 Basis for Temperature Gradients.................................................................... 3-69

Table 5-1 Maximum Design Water Velocity at Different Scour Protections................... 5-8

Table 5-2 Normal Thickness of Arch Barrel (Arch Ring) .............................................. 5-19Table 5-3 Suppliers of Premade Bridges ........................................................................ 5-26

Table 6-1 Resistance Factors for Strength Limit State for Shallow Foundations............. 6-3Table 6-2 Resistance Factors for Geotechnical Strength Limit State in

Axially Loaded Piles......................................................................................... 6-4

Table 6-3 Resistance Factors for Geotechnical Strength Limit State in

Axially Loaded Drilled Shafts .......................................................................... 6-5


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Table 6-4 Resistance Factors for Buried Structures ........................................................ 6-13

Table 6-5 Flexibility Factor Limit ...................................................................................6-14

Table 7-1 Values for Cohesion Factor, c, and Friction Factor, ......................................7-5Table 7-2 Material Properties of Different Arch Bridge Stones......................................7-13

Table 8-1 Permissible Stresses (Mpa) for Filled PTFE Bearings......................................8-8Table 8-2 Design Coefficients of Friction Service Limit State ......................................8-9

Table 8-3 Shear Modulus G.............................................................................................8-10

Table 8-4 Low-Temperature and Minimum Grades of Elastomer ..................................8-11Table 8-5 Steel-Reinforced Elastomeric Bearing Balanced Design .............................8-16

Table 9-1 Grades of Concrete and Characteristic Cylinder and CubeCompressive Strength, fck..................................................................................9-3

Table 9-2 Grades and Classes of Concrete ........................................................................9-3

Table 9-3 Grades of Concrete and Values of fctk and fctm ..................................................9-6

Table 9-4 Tensile Requirements for Reinforcement Bars .................................................9-6Table 9-5 Cover for Unprotected Main Reinforcing Steel (mm) ......................................9-7

Table 9-6 Classes of Tension Lap Splices .......................................................................9-11

Table 9-7 Resistance Factors ...........................................................................................9-17

Table 10-1 Minimum Mechanical Properties of Structural Steel ......................................10-2

Table 10-2 Reinforce Factors [] for the Strength Limit State .........................................10-4

Table 11-1 Timber Stress Values [Mpa]............................................................................11-2

Table 11-2 Characteristic Timber Values for Flexural and Deformation Design .............11-3

Table 11-3 Size Effect Factor, CF, for Sawn Dimension Lumber .....................................11-3

Table 11-4 Deck Factors, CD, for Mechanically Laminated Solid Sawn Lumber Decks..11-4Table 11-5 Resistance Factors, , for Wood .....................................................................11-4Table 11-6 Tolerances for Masonry................................................................................... 11-5

Table 11-7 Material Properties of Different Bridge Stones............................................... 11-6

Table 12-1 Comparison between Bedrock Acceleration Coefficients...............................12-4

Table 12-2 Factor kh for Relative Humidity ....................................................................12-19Table 12-3 Normal Thickness of Arch Barrel (Arch Ring).............................................12-45

Table 12-4 K-Values for Effective Length of Arch Ribs ................................................ 12-46

Table 12-5 Suitability of Different Bearing Types.......................................................... 12-54

Table 13-1 Equivalent Strips for Different Types of Decks..............................................13-4

Table 13-2 L for Use in Live Load Distribution Factor Equations.............................. 13-11

Table 13-3 Distribution of Live Load per Lane for Moment in Interior Beam ...............13-13

Table 13-4 Distribution of Live Loads per Lane for Moment in ExteriorLongitudinal Beams ......................................................................................13-14

Table 13-5 Reduction of Load Distribution Factors for Moment in Longitudinal

Beams on Skewed Supports ..........................................................................13-15Table 13-6 Distribution of Live Load per Lane for Transverse Beams for

Moment and Shear.........................................................................................13-15


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Table 13-7 Distribution of Live Load per Lane for Shear in Interior Beams ................. 13-16

Table 13-8 Distribution of Live Load Per Lane for Shear in Exterior Beams................ 13-17

Table 13-9 Correction Factors for Load Distribution Factors for SupportShear of the Obtuse Corner........................................................................... 13-17

Table 13-10 Values of and for Section with Transverse Reinforcement.................... 13-23

Table 13-11 Values of and for Section without Transverse Reinforcement............... 13-23

Table 14-1 Unit Weights of Materials ............................................................................ 14-10

Table 14-2 Condition of Wearing Surface and Impact Value......................................... 14-14

Table 14-3 Reinforcing Steel Yield Stresses .................................................................. 14-14Table 14-4 Correction Factor for Analysis ..................................................................... 14-16

Table 14-5 Load Factors ................................................................................................. 14-17

Table 14-6 Resistance Factors vs. Condition.................................................................. 14-20

Table 14-7 Resistance Factors for All Conditions....................................................... 14-21Table 14-8 Reduction Factors for Live Load.................................................................. 14-22

Table 14-9 Centrifugal Distribution Factor Ap ............................................................... 14-25

Table 14-10 Barrel Factor ................................................................................................ 14-31Table 14-11 Fill Factor ..................................................................................................... 14-31

Table 14-12 Width Factor ................................................................................................ 14-32

Table 14-13 Mortar Factor ............................................................................................... 14-32

Table 14-14 Depth Factor ................................................................................................ 14-32Table 14-15 Load Capacity and Gross Vehicle Weight Restrictions for

Masonry Arches............................................................................................ 14-36


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Page xviii Ethiopian Roads Authority

Forms

Form 4-1 Field Visit Investigation Form .....................................................................4-10Form 4-2 Bridge Inspection Form................................................................................4-11

Form 12-1 Checklist for Piling Design (Driven Piles).................................................12-11Form 12-2 Checklist for Masonry Piers Design...........................................................12-21Form 12-3 Checklist for RC Frame Pier Design..........................................................12-23

Form 12-4 Checklist for Masonry Abutments Design .................................................12-24

Form 12-5 Checklist for RC Abutment Design............................................................12-25Form 12-6 Checklist for Single Span RC Slab Design ................................................12-34

Form 12-7 Checklist for Single Span RC Deck Girder Design ...................................12-39

Form 12-8 Checklist for Frame Bridge Design............................................................12-43Form 12-9 Checklist for Masonry Arch Bridge Design...............................................12-46

Form 12-10 Checklist for Prestressed Superstructure Design........................................12-52

Form 12-11 Checklist for Bearing Design .....................................................................12-53

Form 12-12 Checklist for Basic Steps for the Design of Concrete Bridges................... 12-58


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Bridge Design Manual - 2002 Glossary

Ethiopian Roads Authority Page xix

GLOSSARY

Bridges may be categorized according to their main use, such as highway bridges, railway

bridges, pedestrian bridges, etc. They may also be sorted according to the material used in

their construction, such as reinforced concrete bridges, steel bridges, stone bridges, timber

bridges, etc. They may also be sorted into rigid, removable and floating bridges.

In this manual, the type of design is used to categorize the bridges: slab bridges and girder

bridges, which are called framed if the slabs or beams are rigid at the supports, tube bridges,arch bridges, truss bridges, cable bridges and suspension bridges.

Apart from these means of grouping bridges, there are a great number of combinations andvariations.

The following definitions apply to this manual:

Active Earth Pressure Lateral pressure resulting from the retention of the earth by astructure or component that is tending to move away from the soil mass.

Active Earth Wedge Wedge of earth with a tendency to become mobile if not retained bya structure or component.

Accidental design situation Design situation involving exceptional conditions of thestructure or its exposure, e.g. collision, explosion, impact or local failure.

Aeroelastic Vibration Periodic, elastic response of a structure to wind.

Anchorage In post-tensioning, a mechanical device used to anchor the tendon to theconcrete; in pretensioning, a device used to anchor the tendon the tendon until the

concrete has reached a predetermined strength and the prestressing force has been

transferred to the concrete; for reinforcing bars, a length of reinforcement, or amechanical anchor or hook, or combination thereof, at the end of a bar needed totransfer the force carried by the bar into the concrete.

Appurtenances Curbs, parapets, railings, barriers and lighting posts attached to the bridge

deck

Arching Action A structural phenomenon in which wheel loads are transmitted primaryby compressive struts formed in the slab.

Axle Unit Single axle or tandem axle.

Band A strip of laminated wood deck within which the pattern of butt joints is not

repeated.

Basal Heave The inflation at the bottom of a wall

Bolster A spacer between a metal deck and a beam.

Bridge A structure with a of total clear opening above 6.0-m. A structure with a clear span

opening less than that is a culvert. Small bridge 6-15 m, Medium 15-50 m and Large

bridge above 50 m total length.

Bulkhead A steel element attached to the side of stress laminated timber decks todistribute the prestressing force and reduce the tendency to crush the wood.


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Cellular Deck A concrete deck with void-ratio in excess of 40 percent.

Centrifugal Force A lateral force resulting from a change in the direction of a vehicle'smovement.

Chord Top member of a (half-through) truss

Clearance: The minimum height between the top surface of the roadway or shoulder andthe bottom surface of the superstructure of the bridge.

Clear span The face-to-face distance between supporting components (=clear opening)

Closed Rib A rib in an orthotropic deck consisting of a plate forming a trough, welded tothe deck plate along both sides of the rib.

Closure Joint A cast-in-plac e concrete fill between precast components to provide

continuity.

Combination of actions Set of design values used for the verification of the structuralreliability for a limit state under the simultaneous influence of different actions.

Combination values Values associated with the use of combinations of actions to take

account of a reduced probability of simultaneous occurrence of the most unfavorablevalues of several independent actions.

Compatibility the equality of deformation at the interface of elements and/or componentsjoined together.

Component A structural element or combination of elements requiring individual designconsideration.

Composite Action A condition in which two or more elements or components are made toact together by preventing relative moment at their interface.

Composite Construction Concrete components or concrete and steel components

interconnected to respond to force effects as a unit.

Concrete Cover The specified minimum distance between the surface of the reinforcingbars, strands, post-tensioning ducts, anchorages or other embedded items, and the

surface of the concrete.

Continuity In decks, both structural continuity and the ability to prevent water penetrationwithout the assistance of nonstructural elements.

Core Depth The distance between the top of top reinforcement and the bottom of bottomreinforcement in a concrete slab.

Counter Diagonal Bracing of a truss

Creep Time-dependent deformation of concrete under permanent load.

Culvert A structure with a maximum of 6.0-m total clear opening. A structure with a clearspan opening above that is a bridge.

Deck A component, with or without wearing surface, that supports wheel loads directlyand is supported by other components.

Deck Joint A complete or partial interruption of the deck to accommodate relativemoment between portions of a structure.


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Deck System A superstructure, in which the deck is integral with its supportingcomponents, or in which the effects or deformation of supporting components on the

behavior of the deck is significant.

Design criteria The quantitative formulations, which describe for each limit state theconditions to be fulfilled.

Design Lane A notional traffic lane positioned transversely on the roadway.

Design span The center-to-center distance between the adjacent supporting components(i.e. bearings), taken in the primary direction (= theoretical span length).

Design Water Depth Depth of water at mean high water.

Design Water flow The statistical flow, which occurs in a certain design period, usuallyevery 50 or 100 years.

Design Water level The statistical water level, which occurs in a certain design period,usually every 50 or 100 years. Sometimes called highest high water level or

maximum water level.

Design working life The assumed period for which a structure is to be used for itsintended purpose with anticipated maintenance but without substantial repair beingnecessary, usually 100-120 years for bridges.

Dynamic Load Allowance An increase in the applied static force effects to account for thedynamic interaction between the bridge and moving vehicles.

Effective Length The span length used in the empirical design of concrete slabs.

Elastic A structural response in which stress is directly proportional to strain and nodeformation remains upon removal of loading.

Engineer Person responsible for the design of the bridge

Equilibrium A state where the sum of forces parallel to any axis and the sum of moments

about any axis in space, are 0.0.

Equivalent Strip An artificial linear element, isolated from a deck for the purpose ofanalysis, in which extreme force effects calculated for a line of wheel loads,

transverse or longitudinal, will approximate those actually taking place in the deck.

Equivalent Fluid A notional substance whose density is such that it would exert the samepressure as the soil it is seen to replace for computational purposes.

Extreme A maximum or a minimum.

Falsework A framework of wood or steel used to support forms for the construction of RCslab spans or girders, or to provide temporary support for structural units (stonemasonry arch) during the construction or reconstruction of permanent supports.

Flexural Continuity The ability to transmit moment and rotation between components orwithin a component.

Floorbeam The traditional name for a cross-beam.

Footprint The specified contact area between wheel and roadway surface.

Form of structure The arrangement of structural elements, such as beam, column, archand foundation piles. Forms of structure are, for example, frames, suspension bridges.


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Frame Action Transverse continuity between the deck and the webs of cellular cross-section or between the deck and primary components in large bridges.

Free (clear) opening Same definition as clear span

Freeboard The clearance (clear height) between the design water level and the bottomsurface of the superstructure of the bridge.

Friction Pile A pile whose support capacity is derived principally from soil resistancemobilized along the side of the embedded pile.

Frontwall The part of a frame bridge below the bridge deck; or the abutment facing theopening (stem).

Global Pertinent to the entire superstructure or to the whole bridge. The opposite to local.

Glued Laminated Deck Panel A deck panel made from wood laminations connected by

adhesives.

Governing Position The location and orientation of a transient load to cause extreme forceeffects.

Gusset plate Plate material used to interconnect vertical, diagonal and horizontal trussmembers at a panel point.

Inelastic The structural response in which stress is not directly proportional to strain anddeformation may remain upon removal of loading.

Influence Surface A continuous or discretized function over a bridge deck whose value ata point, multiplied by a load acting normal to the deck at that point, yields the force

effect being sought.

Interface The location where two elements and/or components are in contact.

Internal Composite Action The interaction between a deck and a structural overlay.

Isotropic Plate A plate having essentially identical structural properties in the twoprincipal directions.

Isotropic Reinforcement Two identical layers of reinforcement, perpendicular to and intouch with each other.

Lateral Any horizontal or close to horizontal direction.

Laminated Deck A deck consisting of a series of laminated wood elements that are tightlyabutted along their edges global analysis.

Lever Rule The statical summation of moments about one point to calculate the reaction ata second point.

Liquefaction The loss of shear strength in a saturated soil due to excess hydrostatic

pressure. In saturated, cohesionless soils, such a strength loss can result from loadsthat are applied instantaneously or cyclicly, particularly in loose fine to medium

sands that are uniformly graded.

Load The effect of acceleration, including that due to gravity, imposed deformation, orvolumetric change.

Load arrangement Identification of the position, magnitude and direction of a free action.


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Load case Compatible load arrangements, sets of deformations and imperfectionsconsidered simultaneously with fixed variable actions and permanent actions for a

particular verification.

Local Analysis An in-depth study of strains and stresses in or among components usingforce effects obtained from global analysis.

Maintenance The total set of activities performed during the working life of the structureto preserve its function.

Megagram (Mg) 1 000 kg = 1.0 metric ton (a unit of mass).

Mode of Vibration A shape of dynamic deformation associated with a frequency ofvibration.

Moisture Content An indication of the amount of water contained in the wood, usuallyexpressed as a percentage of the mass of the oven dry wood

Net Depth The depth of concrete, excluding the concrete placed in the corrugations of a

metal formwork.

Nominal Load An arbitrarily selected design load level.Normally Consolidated Soil A soil for which the current overburden pressure is the

greatest that has been experienced.

Open Grid Floor A metal grid floor net filled or covered with concrete.

Open Rib A rib in an orthotropic deck consisting of a single plate or rolled section weldedto the deck plate.

Orthotropic A plate having significantly different structural properties in the twoprincipal directions.

Over consolidated Soil A soil that has been under greater overburden pressure than

currently exists.

Overconsolidation Ratio OCR = Maximum Preconsolidation Pressure

Overburden Pressure

Partial Composite Action A condition in which two or more elements or components are

made to act together by decreasing, but not eliminating, relative movement at their

interface, or where the connecting elements are too flexible to fully develop the deck

in composite action.

Passive Earth Pressure Lateral pressure resulting from the earth's resistance to the lateralmovement of a structure or component into the soil mass

Permanent Loads Loads and forces that are, or are assumed to be, constant upon

completion of construction.Permit Vehicle Any vehicle whose right to travel is administratively restricted in any way

due to its weight or size.

Post-Tensioning Duct A form device used to provide a path for post-tensioning tendonsor bars in hardened concrete.

Primary Direction In isotropic decks: direction of the shorter span; in orthotropic decks:direction of the main load carrying elements.


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Point Bearing Pile A pile whose support capacity is derived principally from theresistance of the foundation material on which the tip rests.

Reliability Reliability covers safety, serviceability and durability of a structure.

Reliability Index A quantitative assessment of safety expressed as the ratio of thedifference between the mean resistance and mean force effect to the combined

standard deviation of resistance and force effect.

Resistance Mechanical property of a component, a cross-section, or a member of astructure, e.g. bending resistance, buckling resistance.

Roadway The portion of the highway within the limits of construction and all structures,ditches, channels and waterways that are necessary for the correct drainage thereof.

Roadway Width Clear space between barriers and/or curbs.

Scupper Drain outlet in bridge deck without (sand) trap.

Segmental concrete bridge A concrete bridge made up of individual elements, eitherprecast or cast-in place, and posttensioned together to act as a monolithic unit under

loads.Setting Temperature A structure's average temperature, which is used to determine the

dimensions of a structure when a component is added or set in place.

Serviceability limit states States, which correspond to conditions beyond which specified

service requirements for a structure or structural element are no longer met.

Shear Key A preformed hollow in the side of a precast component filled with grout or asystem of match-cast depressions and protrusions in the face of segments that isintended to provide shear continuity between components.

Shoulder The portion of the roadway contiguous with the traveled way foraccommodation of stopped vehicles, for emergency use and for lateral support of

base and surface courses.Skew or skew angle The acute angle between two centerlines which cross.

Sidewalk The portion of the roadway constructed primarily for the use of pedestrians andor bicycles.

Span length For simple spans: the distance center to center of supports but need notexceed clear span plus thickness of slab. For members that are not built integrally with their

supports: the clear span plus the depth of the member but need not exceed the distance

between centers of supports

Spandrel walls The sidewalls parallel to the alignment, resting on the arch barrel (arch

ring).

Stage Construction Construction taking place over fixed and distinct time frames.

Strategic bridges Bridges across wide, flowing rivers (Blue Nile, Awash, Omo) whichcannot easily be replaced by a temporary bridge such as a 40 m span double Baileytruss bridge.

Strategic roads Important roads very far away from parallel, alternative roads (e.g.- the

Addis-Gondar road).

Strength Mechanical property of a material, usually given in units of stress.


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Structure Organized combination of connected parts designed to provide some measure ofrigidity or a construction works having such an arrangement. Bridges, culverts, catch

basins, inlets, retaining walls, buildings, steps, fences, service pipes, underdrains,foundation drains and other features that may be encountered in the work and are not

otherwise classed herein.

Structural system The load-bearing elements of a building or civil engineering works andthe way in which these elements function together.

Substructure The part of a structure that is below the bearings of simple and continuousspans, skewbacks of arches and top of footings of rigid frames, together with the

back walls, wingwalls and wing protection railings.

Superstructure Structural parts of the bridge that provide the horizontal span.

Surcharge A load used to model the weight of earth fill or other loads applied to the top ofthe retained material.

Tandem Two closely spaced axles, usually connected to an under-carriage, which aids indistributing the load equally.

Tendon A high-strength steel element used to prestress the concrete.

Total (overall) bridge length The distance between the rear ends of the wingwalls orabutments and shall be measured parallel to the alignment between the rear ends of the

wingwalls or abutments.

Transient design situation Design situation which is relevant during a period muchshorter that the design working life of the structure and which has a high probability

of occurrence. It refers to temporary conditions of the structure, of use, or exposure,

e.g. during construction or repair.

Ultimate limit states States associated with collapse, or with other similar forms of

structural failure. They generally correspond to the maximum load-carrying

resistance of a structure or structural part.

Wall Friction Angle An angle whose arctangent represents the apparent friction between awall and a soil mass.

Wheel Single or dual tire at one end of an axle.

Wheel Line A transverse or longitudinal grouping of wheels.

Work All the work specified, indicated, shown or contemplated in the Contract toconstruct the improvement, including all alterations, amendments or extensions thereto madeby contract change order, supplemental agreement or other written orders by the Engineer.


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Abbreviations Bridge Design Manual - 2002

ABBREVIATIONS

AASHTO - American Association of State Highway and Transportation Officials

AISC - American Institute of Steel ConstructionASA - American Standards Association

ASTM - American Society for Testing Materials

CAPWAP - Case Pile Wave Analysis Program

DIM - Dimensionless

EBCS - Ethiopian Building Code Standard

ENR - Engineering News Formula

ERA - Ethiopian Roads Authority

ISO - International Standard Organization

MEXE - Military Engineering Experimental Establishment

PTFE - Polytetrafluorethylene (also known as Teflon)

QSA - Quality & Standardization Authority of EthiopiaSI - The International System of Units

UDL - Uniform Distributed Load