HDS7 - Hydraulic Design of Safe Bridges

1 Department of Transportation Federal Highway administration Publication No. FHWA-HIF-12-018 April 2012 Hydraulic Design Series Number 7 Hydraulic Design of safe Bridges Technical Report Documentation Page 1. Report No. FHWA-HIF-12-018 HDS 7 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle Hydraulic Design OF safe Bridges 5. Report Date April 2012 6. Performing Organization Code 7. Author(s) Zevenbergen, Arneson, Hunt, Miller 8. Performing Organization Report No. 9. Performing Organization Name and Address Ayres Associates 3665 JFK Parkway Building 2, Suite 200 Fort Collins, Colorado 80525 10. Work Unit No. (TRAIS) 11. Contract or Grant No. DTFH61-06-D-00010 12. Sponsoring Agency Name and Address Office of bridge Technology National Highway Institute FHWA, Room 3203 1310 North Courthouse Rd., Suite 300 400 Seventh Street, SW Arlington, Virginia 22201 Washington, 20590 13.

2 Type of Report and Period Covered 14. Sponsoring Agency Code 15. Supplementary Notes Technical Project Manager: Dr. Arneson (FHWA Resource Center Hydraulics) Technical Assistance: Joe Krolak (FHWA Headquarters Hydraulics) and Dr. Kornel Kerenyi (FHWA Research Hydraulics) 16. This document provides technical information and guidance on the Hydraulic analysis and Design of Bridges . The goal is to provide information such that Bridges can be designed as safely as possible while optimizing costs and limiting impacts to property and the environment. Many significant aspects of bridge Hydraulic Design are discussed. These include regulatory topics, specific approaches for bridge Hydraulic modeling, Hydraulic model selection, bridge Design impacts on scour and stream instability, and sediment transport. 17. Key Words bridge Design , bridge hydraulics, open channel flow, Hydraulic modeling, Hydraulic analysis, scour, stream stability, unsteady flow modeling, sediment transport, fluvial geomorphology 18.

3 Distribution Statement This document is available to the public through the National Technical Information Service, Springfield, VA 22161 (703) 487-4650 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 280 22. Price i TABLE OF CONTENTS LIST OF FIGURES .. vii LIST OF TABLES .. xiii LIST OF SYMBOLS .. xv LIST OF ACRONYMS .. xix GLOSSARY .. xxi ACKNOWLEDGMENTS .. xxxvii CHAPTER 1 - INTRODUCTION .. INTRODUCTION .. Background .. Purpose .. History of bridge Hydraulics .. Hydraulic ANALYSIS OVERVIEW .. MANUAL ORGANIZATION .. Chapter 1 - Chapter 2 - Design Considerations and Regulatory Requirements .. Chapter 3 - Governing Equations and Flow Classification .. Chapter 4 - Hydraulic Analysis Considerations .. Chapter 5 - One-Dimensional bridge Hydraulic Analysis .. Chapter 6 - Two-Dimensional bridge Hydraulic Analysis.

4 Chapter 7 - Unsteady Flow Analysis .. Chapter 8 - bridge Scour Considerations and Scour Countermeasure Hydraulic Analysis .. Chapter 9 - Sediment Transport and Alluvial Channel Concepts .. Chapter 10 - Other Considerations .. Chapter 11 - Literature Cited .. DUAL SYSTEM OF UNITS .. CHAPTER 2 - Design CONSIDERATIONS AND REGULATORY REQUIREMENTS .. INTRODUCTION .. bridge OPENING AND ROAD GRADE Design CONSIDERATIONS .. FLOODPLAIN AND FLOODWAY REGULATIONS .. SCOUR AND STREAM STABILITY CONSIDERATIONS AND GUIDANCE .. NAVIGATION REQUIREMENTS .. SECTION 404 REQUIREMENTS .. AASHTO SPECIFICATIONS AND Design CRITERIA .. CHAPTER 3 - GOVERNING EQUATIONS AND FLOW CLASSIFICATION .. INTRODUCTION .. Streamlines and Streamtubes .. Definitions .. Classification of Open Channel Flow .. ii THREE BASIC EQUATIONS OF OPEN CHANNEL FLOW.

5 Conservation of Conservation of Energy .. Conservation of Linear Momentum .. FLOW RESISTANCE AND OTHER Hydraulic EQUATIONS .. Flow Resistance .. Drag Force .. Weir Flow .. Gate and Orifice Equations .. FLOW CLASSIFICATION .. Steady Versus Unsteady Flow .. Subcritical Versus Supercritical Flow .. Uniform, Gradually, and Rapidly Varied Flow .. Profiles for Gradually Varied Flow .. CHAPTER 4 - Hydraulic ANALYSIS CONSIDERATIONS .. INTRODUCTION .. Hydraulic MODELING CRITERIA AND SELECTION .. One-Dimensional Versus Two-Dimensional Modeling .. Steady Versus Unsteady Flow Modeling .. Three-Dimensional Modeling and Computational Fluid Dynamics .. Physical Modeling .. SELECTING UPSTREAM AND DOWNSTREAM MODEL EXTENT .. IDENTIFYING AND SELECTING MODEL BOUNDARY CONDITIONS .. Water Surface .. Normal Depth and Energy Slope.

6 Rating Curve .. Critical Depth .. RIVERINE HYDROLOGIC INFORMATION .. NUMERICAL MODEL EVALUATION .. DATA REQUIREMENTS AND SOURCES .. CHAPTER 5 - ONE-DIMENSIONAL bridge Hydraulic ANALYSIS .. INTRODUCTION .. HDS 1 METHOD .. WATER SURFACE PROFILE COMPUTATIONS .. Standard-Step Methods .. Other Water Surface Profile Methods .. Mixed-Flow Regime .. iii CROSS-SECTION SUBDIVISION AND INEFFECTIVE FLOW .. Cross Section Subdivision .. Ineffective Flow .. FLOW CONSTRICTIONS AND CROSS-SECTION PLACEMENT .. Effects of Highway Crossings .. Cross Section Placement .. Ineffective Flow Specifications at Bridges .. bridge Hydraulic CONDITIONS .. Free-Surface bridge Flow .. Overtopping-Flow .. Flow Submerging the bridge Low Chord .. bridge MODELING APPROACHES .. Modeling Approaches for Free-Surface bridge Flow Conditions.

7 Selection of Free-Surface bridge Flow Modeling Approach .. Modeling Approaches for Overtopping and Orifice bridge Flow .. Selection of the Overtopping and Submerged-Low-Chord Modeling Approach .. SPECIAL CASES IN ONE-DIMENSIONAL HYDRAULICS .. Skewed Crossing Alignment .. Crossings with Parallel Bridges .. Split Flow Conditions .. Crossings with Multiple Openings in the Embankment .. Lateral Weirs .. ONE-DIMENSIONAL MODELING ASSUMPTIONS AND LIMITATIONS .. Water Surface, Velocity, and Cross Section Orientation .. Total Energy and Flow Distribution .. Cross Section Spacing .. Assumptions for Multiple Openings .. Cross-Section, bridge , and Pier Skew .. CHAPTER 6 - TWO-DIMENSIONAL bridge Hydraulic ANALYSIS .. INTRODUCTION .. GOVERNING EQUATIONS .. TYPES OF TWO-DIMENSIONAL MODELS .. Finite Element Method .. Finite Difference Method.

8 GEOMETRIC REQUIREMENTS AND MESH QUALITY .. Geometric Requirements .. Mesh Quality .. iv bridge MODELING APPROACHES .. Pier Pressure Flow .. Weir Flow and Road Overtopping .. MULTIPLE OPENINGS IN AN EMBANKMENT .. MULTIPLE OPENINGS IN SERIES .. UPSTREAM FLOW DISTRIBUTION .. SPECIAL CASES IN TWO-DIMENSIONAL MODELING .. Split Flow .. Lateral Weirs .. Culverts .. Debris .. TWO-DIMENSIONAL MODELING ASSUMPTIONS AND REQUIREMENTS .. Gradually Varied Flow .. Flow Distribution and Water Surface at Boundaries .. Model Step-Down and Convergence .. Wetting and Drying .. CHAPTER 7 - UNSTEADY FLOW ANALYSIS .. INTRODUCTION .. Unsteady Flow Equations - Saint-Venant Equations .. Unsteady Continuity Equation .. Dynamic Momentum Equation .. MODEL UPSTREAM AND DOWNSTREAM EXTENTS .. DIFFERENCES BETWEEN STEADY AND UNSTEADY FLOW ANALYSIS.

9 SOLUTION SCHEMES FOR THE SAINT-VENANT EQUATIONS .. CHANNEL AND FLOODPLAIN CROSS SECTION .. STORAGE AREAS AND CONNECTIONS .. Hydraulic PROPERTY TABLES .. NUMERICAL STABILITY .. TWO-DIMENSIONAL UNSTEADY FLOW MODELS .. TIDAL WATERWAYS .. CHAPTER 8 - bridge SCOUR CONSIDERATIONS AND SCOUR COUNTERMEASURE Hydraulic ANALYSIS .. INTRODUCTION .. SCOUR CONCEPTS FOR bridge Design .. TYPES OF SCOUR .. Contraction Local Scour .. Debris Channel Instability .. Evaluating Channel Instability .. v COMPUTING SCOUR .. One-Dimensional Models .. Two-Dimensional Models .. Hydraulic ANALYSIS OF SCOUR COUNTERMEASURES .. Revetments and Vegetation .. Guide Banks .. Spurs and Bendway Weirs .. CHAPTER 9 - SEDIMENT TRANSPORT AND ALLUVIAL CHANNEL CONCEPTS .. INTRODUCTION .. SEDIMENT CONTINUITY.

10 SEDIMENT TRANSPORT CONCEPTS .. Initiation of Motion .. Modes of Sediment Transport .. OVERVIEW OF SEDIMENT TRANSPORT EQUATIONS AND SELECTION .. OVERVIEW OF SEDIMENT TRANSPORT MODELING .. ALLUVIAL FANS .. CHAPTER 10 - OTHER CONSIDERATIONS .. Hydraulic FORCES ON bridge ELEMENTS .. General .. Hydrostatic Force .. Buoyancy Force .. Stream Pressure and Lift .. Wave Forces .. Effects of Debris .. Effects of Ice .. Vessel Collision .. BACKWATER EFFECTS OF bridge PIERS .. COINCIDENT FLOWS AT CONFLUENCES .. Significance of Coincident Flows at Confluences .. Available Guidance .. ADVANCED bridge HYDRAULICS MODELING .. Background .. Applications of Advanced Modeling .. Example of Advanced Modeling Applied to bridge Design Projects .. Limitations of Advanced Modeling .. vi bridge DECK DRAINAGE Design .