Highway Bridge Superstructure

Transcription

1 Highway Bridge Superstructure Engineering LRFD Approaches to Design and Analysis Narendra Taly CRC Press Taylor & Francis Group Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Croup, an informa business

2 Preface Acknowledgments x'x xxiii Chapter 1 Introduction Structural Design Philosophies General Design Concepts Fundamentals of Structural Design Philosophies Design Philosophies Based on Elastic Behavior: Allowable/ Working Stress Design Design Philosophies Based on Inelastic Behavior: Plastic Design Method Limit States Design Philosophies Concepts of Limit States Strength Limit States Serviceability Limit States Fatigue Limit States Strength Limit States versus Serviceability Limit Stales Strength Design, Load Factor Design, and Load and Resistance Factor Design Strength Design Philosophy Strength Design Concept Load Factor Design Load and Resistance Factor Design LRFD Specifications for Highway Bridges Evolution of LRFD Specifications for the Design of Steel Buildings in the United States Evolution of LRFD Specifications for Highway Bridges in the United States Why the Change from AASHTO Standard Specifications? Why Probability-Based Design Philosophy? Issues and Considerations for the Development of AASHTO LRFD Criteria Probabilistic Basis of AASHTO LRFD Bridge Design Specifications Statistical Nature of Loads and Resistances Random Variables, Normal and Lognormal Distributions, and Probability Properties and Applications of Normal (Gaussian) Distribution Linear Functions of Random Variables: Central Limit Theorem (CLT, Normal Convergence Theorem) Probabilistic Determination of Safety Factors Probabilistic Concept of Safety: Limit State Function (Performance Function) 39

3 viii Development of AISC LRFD Criteria Development of AASHTO LRFD Criteria Calibration Procedure Calibration of Load and Resistance Factors AASHTO LRFD Specifications Format of Load and Resistance Relationship Loads, Resistance, and Factor of Safety Differences between Various Design Methods: Summary Difference between the Design Methods Based on the Elastic and Inelastic Material Behavior Difference between Plastic Design, Strength Design, Load Factor Design, and Load and Resistance Factor Design Historical Review of AASHTO Specifications for Highway Bridges AASHTO LRFD Highway Bridge Design Specifications and Design Philosophies AASHTO Interim Speci fications Scope of the AASHTO LRFD Bridge Design Specifications Commentary to AASHTO LRFD Specifications General Comments 67 l.a Appendix 68 References 70 Chapter 2 Highway Bridge Superstructure Systems Introduction AASHTO LRFD Spec.-Speci fic Highway Bridge Superstructures Description and Design Characteristics of Superstructure Systems in Table RC Deck over Steel Wide Flange Beams of Plate Girders (Type a) Spread-Box Beam Superstructure (Type b) Open Steel or Precast Concrete Box Superstructure (Type c) Cast-in-Place Concrete Multicell Box Girder (Type d) Cast-in-Place RC T-Beam Superstructure (Type e) Adjacent-Prestressed Concrete Box Superstructure (Type f) Adjacent-Prestressed Concrete Box Superstructure with Integral Concrete Deck with or without Transverse Posttensioning (Type g) Precast Concrete Channel Sections with Shear Keys and Concrete Overlay (Type h) Precast Concrete Double-T Girders with Shear Keys, and with or without Transverse Posttensioning and Integral Concrete Deck (Type i) Precast Concrete Single-T Girders with Shear Keys, and with or without Transverse Posttensioning and Integral Concrete Deck (Type./) RC Deck over Prestressed I-Beams or Bulb-T Girders (Type k) Fiber-Reinforced Polymer Highway Superstructure Systems Diaphragms Definition of a Diaphragm Diaphragms in Building Structures 91

4 lx Diaphragms in Bridge Superstructures ASSHTO Standard Specifications for Diaphragms AASHTO LRFD Specifications for Diaphragms and Cross-Frames Bridge Site and Geometry Bridge Type, Size, and Location Bridge Width Normal and Skewed Bridges Deflections Historical Review of Deflection Limitations Purpose of Limiting Bridge Deflections Criteria for Live Load Deflections Optional Criteria for Span-to-Depth Ratios Optional Deflection Criteria for Constant Depth Superstructures Optional Deflection Criteria for Curved Steel Superstructures Deflections Due to Dead Loads Calculation of Live Load Deflections Consideration of Future Widening Constructabil ily Bridge Esthetics 107 References 107 Chapter 3 Loads on Highway Bridge Structures Introduction AASHTO LRFD Highway Bridge Design Philosophy Limit States Concept Loads and Load Designations Load Factors and Load Combinations for Design Loads Selection of Design-Specific Limit States, Load Modifiers, Load Combinations, and Load Factors Load Factors and Load Combinations for Construction Loads Evaluation at the Strength Limit States Evaluation of Deflection at the Service Limit State Load Factors for Jacking and Posttensioning Forces Jacking Forces Force for Posttensioning Anchorage Zones Components of a Highway Bridge Structure Dead Loads on a Highway Bridge Superstructure General Dead Load Due to Deck Slab Dead Load Due to Girders Construction Loads Live Loads on Highway Bridge Superstructures Historical Perspective Development of AASHTO Standard Specifications Live Load Model 131

5 X Description of AASHTO LRFD Notional Live Load Model Understanding the Development of AASHTO LRFD Notional Live Load Model Concept of Notional Load: What Is It? Commercial Vehicular Loads Development of AASHTO LRFD Notional Live Load: A Brief History Permit Loads Application of Design Vehicular Live Loads on Bridge Superstructures Position of Live Load on Simple Spans Position of Vehicular Live Loads on Continuous Spans Bending Moments and Shears Due to Moving Loads on Simple Spans Bending Moments Influence Lines for Absolute Maximum Bending Moments in Simple Spans Generalized Expressions for Maximum Moment and Maximum Shear at a Section in a Simple Span Due to HS20 Truck Maximum Moment and Shear: HS20 Truck Moving from Left to Right Maximum Moment and Shear: HS20 Truck Moving from Right to Left Absolute Maximum Bending Moment in Spans Due to Loads Other than AASHTO HS20 Truck Governing Span Lengths for Maximum Live Load Shear in Simple Spans Due to AASHTO LRFD Live Load: HS20 Truck and Tandem Influence Lines for Beams with Other Support Conditions and for Other Types of Structures Dynamic Effects of Vehicular Live Load General Considerations for Dynamic Force Effects: Dynamic Load Allowance Research on Quantification of Dynamic Load Effects AASHTO LRFD Specifications for Dynamic Load Allowance Exceptions to Application of Dynamic Load Effects Fatigue Loading Fatigue Phenomenon Magnitude and Configuration of Live Load for Fatigue Considerations Formulas for Maximum Moment and Shear for Fatigue Limit State Loading Maximum Moment for Fatigue Limit State Maximum Shear for Fatigue Limit State Frequency of Loading for Fatigue Design Considerations Application of ADTTS, for Determination of Fatigue Limit State Pedestrian Loads Significance of Pedestrian Loading Live Load Due to Sidewalks on Vehicular Bridges 210

6 xl Live Load on Pedestrian and/or Bicycle Bridges Application of Design Live Loads on a Bridge Superstructure Design Live Loads for Longitudinal Beams Live Load for Deflection Considerations Design Live Load for Decks, Deck Systems, and Top Slabs of Box Culverts Live Load on Deck Overhangs Force Effects Due to Live Load in Multiple Traffic Lanes: Multiple Presence of Live Load Design Live Loads in Longitudinal Girders Supporting Bridge Decks Envelopes for Moment and Shear Values Tire Contact Area Point Load versus Distributed Load AASHTO LRFD Specifications for Tire Contact Area Rail Transit Loads Centrifugal Force (CE) Braking Force (BR) Magnitude of Braking Force Application of Braking Forces on a Bridge Vehicular Collision Force (CT) Nature, Causes, and Magnitude of Collision Forces Protection of Structures from Vehicular Collision Force, C7" Protection of Structures from Vessel Collision Force, CV Ice and Snow Loads Ice Loads: General Dynamic Ice Forces on Piers Ice Floes and Modes of Failures Effective Ice Crushing Strength Horizontal Force from Flexing of Moving Ice Influence of Directionality of Ice Forces and the Pier Nose Profile on the Magnitude of Forces Acting on the Pier Snow Loads Wind Loads (WL and WS) Wind Effects on Structures Magnitude of Horizontal Wind Pressure Variation in Wind Velocity with Height Estimation of Wind Loads Wind Pressure on Structure (WS) Wind Pressure on Live Load (WL) Earthquake Forces (EQ) Evolution of Earthquake-Resistant Design Provisions in AASHTO Bridge Design Specifications Philosophy for Design Basis Earthquake Forces Determination of Seismic Forces: Fundamental Concepts AASHTO LRFD Specifications Provisions for Seismic Design of Bridges Seismic Design Philosophy Site Class Characterization Determination of Elastic Seismic Response Coefficient, C,, 278

7 xii Determination of Acceleration Coefficients Design Basis Earthquake Seismic Hazard Characterization: Design Response Spectrum Operational Classification Response Modification Factors Application of Earthquake Forces for Design of Structural Members and Connections in Highway Bridges Determination of Design Basis Earthquake Forces General Single-Span Bridges Calculation of Design Connection Forces for Bridges in Various Seismic Zones Determination of Fundamental Period, T Single-Mode Spectral Analysis Method (SM): Procedure Other Methods of Analysis Earth Pressure: EH, ES, LS, and DD General Determination of Earth Pressure Basic Concepts of Earth Pressure Theories and Calculations of Earth Pressures Theories of Earth Pressures Calculations of Coefficients of Earth Pressures Equivalent-Fluid Method of Estimating Rankine's Lateral Earth Pressures Selection of Backfill Material Effects of Surcharge Loads: ES and LS Nature of Surcharge Loads Uniform Surcharge Loads (ES) Point, Line, and Strip Loads (ES) Effects of Live Load Surcharge Loads: LS Downdrag: DD Seismic Earth Pressure Force Effects Due to Superimposed Deformations: TU, TG, SH, CR, SE, and PS General Temperature-Induced Forces Temperature-Induced Forces Due to Uniform Temperature AASHTO LRFD Provisions for Design Unidirectional Thermal Movements Forces Induced by Temperature Gradient Nature of Heat Flow Problem: Thermal Gradient Effect of Nonlinear Temperature Variation AASHTO LRFD Provisions for Thermal Gradient Analysis Miscellaneous Forces for Design Considerations Friction Forces: FR A Appendix 339 References 346

8 xiii Chapter 4 Structural Analysis of Highway Bridge Superstructures Introduction Load Path in Bridge Structures Analysis for Dead Load on Bridge Superstructures Methods of Structural Analysis for Live Load on Bridge Superstructures Approximate Analysis Methods for Live Loads: The Distribution Factor Concept Considerations for Live Load Distribution Factors for Common Types of Bridge Superstructures General Approach Lever Rule Applicability Criteria for LRFD Live Load Distribution Factors Superstructures with Constant Deck Width and Parallel Girders Superstructures with Varying Deck Width and Splayed Girders Influence of Multiple Loaded Lanes Number of Design or Traffic Lanes on a Bridge Influence of Multiple Design/Traffic Lanes on Girders Supporting the Deck Position of Wheel Loads on Bridge Deck with Respect to Girders Calculations of Distribution Factors for Beams/Girders of Typical Superstructures Formulas for Distribution Factors Distribution Factors for Interior Girders Bending Moment Live Load Distribution Factors for Shear Live Load Distribution Factors for Exterior Girders Influence of Diaphragms on Distribution Factors for Exterior Girders Distribution Factors for Bending Moment Distribution Factors for Shear Special Analysis for Distribution Factors for Bending Moments and Shears in Exterior Girders Correction Factors for Bridge Skew Distribution Factors for Fatigue Limit State Distribution Factors for Deflection Limit State Illustrative Examples: Distribution Factors for Bending Moment and Shear Application of Live Distribution Factors for Design Purposes Distribution Factors for Special Loads with Other Traffic Loads Live Load Distribution Factors for Bending Moments and Shear in Transverse Floor Beams Methods of Refined Analysis Distribution of Lateral Loads in Multibeam Bridges General Lateral Wind Load Distribution in Multibeam Bridges Load Path for Lateral Wind Load Determination of Forces and Bending Moments Due to Lateral Wind Load 423

9 Seismic Load Distribution in Multibeam Bridges Load Path for Earthquake Forces in Multibeam Bridges Design Criteria Earthquake Load Distribution Analysis of Concrete Slabs and Slab-Type Bridges for LRFD Live Loads General Slab-Type Bridges Concrete Decks Analysis of Slab-Type Bridges General LRFD Provisions for the Analysis of Slab-Type Bridges: The Approximate Strip Model Analysis of Deck Systems General Calculation of Force Effects Deflection Analysis of Slab Bridges General Influence of Cracking of Concrete Sections under Service Loads Long-Term Deflections A Appendix 436 References 446 Chapter 5 Concrete Bridges Introduction Concrete Bridges and Aesthetics Corrosion of Concrete Bridges Reinforcing Bar Corrosion Problem Mitigation of Corrosion Problem Treated Reinforcing Steel Concrete Cover for Reinforcing Steel General Protective Requirements Material Properties Concrete for Bridge Construction General Normal-Weight and Structural Lightweight Concrete Coefficient or Thermal Expansion Shrinkage and Creep Modulus of Elasticity of Concrete Modulus of Rupture High-Strength Concrete and Bridge Span Capabilities Reinforcing Steel (Art ) General Reinforcing Bars Prestressing Steel: Art General Modulus of Elasticity of Prestressing Steels: Art Relaxation of Steel 470

10 xv Strength Limit State General Resistance Factors (^-factors) Design Procedures for Flexure in Section 5 of LRFD Specifications Assumption for Service and Fatigue Limit Stales: Art Assumptions for Strength and Extreme-Event Limit Slates General Rectangular Stress Distribution: Art Flexural Members General Nominal Flexural Resistance of Concrete Members with Nonprestressed Reinforcement Nominal Flexural Resistance of Prestressed Concrete Members Flexural Resistance: Art Limits of Reinforcement: Art Provisions for Maximum Reinforcement Provisions for Minimum Reinforcement: Art Control of Cracking by Distribution of Reinforcement: Art Service Limit State Service Load Analysis of Reinforced Concrete Sections Deformations: Art General Requirements Deflection and Camber Fatigue Limit State General Stress Limits for Stresses Due to Fatigue Reinforcing Bars Prestressing Tendons Welded or Mechanical Splices Shear General Check for Shear near Supports Nominal Shear Resistance of a Concrete Section General LRFD Procedures for Designing for Shear Reinforcement for Shear Resistance: Regions Requiring Transverse Reinforcement Minimum Transverse Reinforcement Maximum Spacing of Transverse Reinforcement Shear Stress on Concrete Tensile Capacity of Longitudinal Reinforcement: Art Estimating the Area of Required Nonprestressed Tensile Reinforcement in Concrete Sections Slab-Type Concrete Bridges and Concrete Decks Concrete Decks General Minimum Depth and Cover Requirements Composite Action between Decks and Supporting Beams Skewed Decks 507

11 xvi Edge Support Requirements Design of Cantilever Slabs Design Procedures for Deck Slabs Empirical Design Method Traditional Design Method Empirical Design versus Traditional Design Design Examples Design of Reinforced Concrete T-Beam Superstructures Design of Deck Overhang and Barrier Walls General Traffic Railing Design Forces and Design Criteria Yield Line Analysis for Concrete Traffic Barriers or Parapets Slab-Precast, Prestressed Concrete Bridges Introduction Characteristics of Prestressed Concrete Bridges Use of High-Strength Concrete Shapes, Sizes, and Uses of Precast, Prestressed Concrete Girders Concepts of Prestressing Pretensioned and Posttensioned Girders Layout and Location of the Center of Gravity of Multiple Strands in a Prestressed Girder Design of a Prestressed Concrete Girder for a Highway Bridge A Appendix 682 References 690 Chapter 6 Slab-Steel G i rder Bridges Introduction Structural Forms and Characteristics of Steel Bridges Common Forms of Slab-Steel Beam Bridges Orthotropic Steel Bridges Composite Steel Box Girder Bridges Delta Frame Steel Bridges Corrosion of Steel Bridges Construction Considerations Mechanical Properties of Steel for Highway Bridges Hybrid Steel Girders Noncomposite and Composite Sections Noncomposite Sections Composite Sections Section Properties of Noncomposite and Composite Sections Shored and Unshored Construction Sequence of Loading during Construction Shored Construction Unshored Construction Resistance Factors Design Provisions for I-Section Flexural Members General General Format for LRFD Specifications for Steel Superstructures 709

12 Sequence of Loading and Elastic Stresses Flange-Strength Reduction Factors Cross-Section Proportion Limits Minimum Metal Thickness (LRFD Art ) Web Proportion Limits (LRFD ) Flange Proportion (LRFD Art ) Constructibility Requirements (LRFD Art ) General Dead Load Deflection and Camber Instability of I-Beams: The Lateral-Torsional- Buckling Phenomenon Lateral-Torsional Buckling and Bracing of Beams Flange Stresses and Member Bending Moments Moment Gradient Modifier, Ch Flange Stresses and Member Bending Moments: Critical Stages of Construction Considerations for Service Limit State Permanent Deformations General Flange Stresses Special Fatigue Requirements for Webs Design Requirements for Strength Limit Slate General Composite Sections in Positive Flexure Composite Sections in Negative Flexure and Noncomposite Sections Flexural Resistance of Composite and Noncomposite Sections in Positive Flexure: Strength Limit State Compact Sections in Positive Flexure Noncompact Sections Ductility Requirements: Art Flexural Resistance: Compact Sections in Negative Flexure and Noncomposite Sections Strength Limit State General Requirements Compression Flange Flexural Resistance: Art Shear Resistance General: Shear Strength of Steel Girders Nominal Resistance of Unstiffencd Webs Nominal Resistance of Stiffened Webs: Interior Panels Shear Resistance of End Panels Shear Connectors Role of Shear Connectors Types and Sizes of Shear Connectors Fatigue Limit State: Loads for Fatigue Limit State Fatigue Resistance of Shear Connectors: LRFD Art Pitch of Shear Connectors (Art ) Design of Shear Connectors for Strength Limit Slate (Art ) Strength of Shear Connectors LRFD Provisions for Providing Shear Connectors 754

13 xviii Stiffeners Definitions and Description of Stiffeners Web Bend-Buckling Resistance Design of Transverse Stiffeners Design for Bearing Stiffeners Design for Longitudinal Stiffeners Cover Plates Fatigue and Fracture Considerations General Classification of Fatigue Design for Load-Induced Fatigue Design Considerations Design Criteria Detail Categories Detailing to Reduce Constraint Fatigue Resistance Design of Noncomposite Slab-Steel Girder Superstructures Composite Slab-Steel Beam Superstructures Introduction to Composite Construction Flexural Strength of Composite Sections Stress Distribution in Composite Beams in Positive Flexure Stress Distribution in Composite Beams in Negative Flexure Locating Plastic Neutral Axis of a Composite Section in Positive Flexure Effective Flange Width AASHTO Procedure for Determining the Plastic Neutral Axis and Plastic Moment Strength of a Composite Section: LRFD Appendix D6, Art. D Examples on Determination of Plastic Moment Strength, Mp Yield Moment of Noncomposite Sections: LRFD Art Yield Moment of Composite Sections in Positive Flexure: LRFD Art. D Yield Moment of Composite Sections in Negative Flexure: LRFD Art. D Yield Moment of Composite Sections with Cover Plates: LRFD Art. D Depth of the Web in Compression: Depth of the Web in Compression Region (Dc): Depth of the Web in Compression LRFD Art. D in the Elastic LRFD Art. D at Plastic Moment LRFD Art. D (Dcp): 6.14 Design of Composite Slab-Girder Superstructures A Appendix 906 References 922 Index 925