LRFD Design Example for December 2003 FHWA NHI-04-041 Steel Girder Superstructure Bridge Prepared for FHWA / National Highway Institute Washington, DC US Units Prepared by Michael Baker Jr Inc Moon Township, Pennsylvania Development of a Comprehensive Design Example for a Steel Girder Bridge with Commentary Design Process Flowcharts for Superstructure and Substructure Designs Prepared by Michael Baker Jr. , Inc. November 2003 Technical Report Documentation Page 1. 4. Report No. 2. Government Accession No. 3. 5. Recipient’s Catalog No.
Report Date FHWA NHI - 04-041 Title and Subtitle LRFD Design Example for Steel Girder Superstructure Bridge with Commentary 7. Author (s) December 2003 6. Performing Organization Code Raymond A. Hartle, P. E. , Kenneth E. Wilson, P. E. , S. E. , William A. Amrhein, P. E. , S. E. , Scott D. Zang, P. E. , Justin W. Bouscher, E. I. T. , Laura E. Volle, E. I. T. 8. Performing Organization Report No. B25285 001 0200 HRS 10. 11. 13. Work Unit No. (TRAIS) Contract or Grant No. 9. Performing Organization Name and Address Michael Baker Jr. , Inc.
Related reading: Padma Bridge ParagraphAirside Business Park, 100 Airside Drive Moon Township, PA 15108 12. Sponsoring Agency Name and Address DTFH61-02-D-63001 Type of Report and Period Covered Federal Highway Administration National Highway Institute (HNHI-10) 4600 N. Fairfax Drive, Suite 800 Arlington, Virginia 22203 15. Supplementary Notes Final Submission August 2002 - December 2003 14. Sponsoring Agency Code Baker Principle Investigator: Raymond A. Hartle, P. E. Baker Project Managers: Raymond A. Hartle, P. E. and Kenneth E. Wilson, P. E. , S. E. FHWA Contracting Officer’s Technical Representative: Thomas K.
Saad, P. E. Team Leader, Technical Review Team: Firas I. Sheikh Ibrahim, Ph. D. , P. E. 16. Abstract This document consists of a comprehensive steel girder bridge design example, with instructional commentary based on the AASHTO LRFD Bridge Design Specifications (Second Edition, 1998, including interims for 1999 through 2002). The design example and commentary are intended to serve as a guide to aid bridge design engineers with the implementation of the AASHTO LRFD Bridge Design Specifications, and is offered in both US Customary Units and Standard International Units.
This project includes a detailed outline and a series of flowcharts that serve as the basis for the design example. The design example includes detailed design computations for the following bridge features: concrete deck, steel plate girder, bolted field splice, shear connectors, bearing stiffeners, welded connections, elastomeric bearing, cantilever abutment and wingwall, hammerhead pier, and pile foundations. To make this reference user-friendly, the numbers and titles of the design steps are consistent between the detailed outline, the flowcharts, and the design example.
In addition to design computations, the design example also includes many tables and figures to illustrate the various design procedures and many AASHTO references. AASHTO references are presented in a dedicated column in the right margin of each page, immediately adjacent to the corresponding design procedure. The design example also includes commentary to explain the design logic in a user-friendly way. Additionally, tip boxes are used throughout the design example computations to present useful information, common practices, and rules of thumb for the bridge designer.
Tips do not explain what must be done based on the design specifications; rather, they present suggested alternatives for the designer to consider. A figure is generally provided at the end of each design step, summarizing the design results for that particular bridge element. The analysis that served as the basis for this design example was performed using the AASHTO Opis software. A sample input file and selected excerpts from the corresponding output file are included in this document. 17. Key Words 18. Distribution Statement
Bridge Design, Steel Girder, Load and Resistance Factor Design, LRFD, Concrete Deck, Bolted Field Splice, Hammerhead Pier, Cantilever Abutment, Wingwall, Pile Foundation 19. Security Classif. (of this report) 20. Security Classif. (of this page) This report is available to the public from the National Technical Information Service in Springfield, Virginia 22161 and from the Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. 20402. 21. No. of Pages 22. Price Unclassified Form DOT F 1700. 7 (8-72) Unclassified 644 Reproduction of completed page authorized
This page intentionally left blank ACKNOWLEDGEMENTS We would like to express appreciation to the Illinois Department of Transportation, Washington State Department of Transportation, and Mr. Mike Grubb, BSDI, for providing expertise on the Technical Review Committee. We would also like to acknowledge the contributions of the following staff members at Michael Baker Jr. , Inc. : Tracey A. Anderson Jeffrey J. Campbell, P. E. James A. Duray, P. E. John A. Dziubek, P. E. David J. Foremsky, P. E. Maureen Kanfoush Herman Lee, P. E. Joseph R. McKool, P. E. Linda Montagna V. Nagaraj, P. E. Jorge M. Suarez, P. E.
Scott D. Vannoy, P. E. Roy R. Weil Ruth J. Williams Table of Contents 1. Flowcharting Conventions 2. Flowcharts Main Flowchart Chart 1 - General Information Chart 2 - Concrete Deck Design Chart 3 - Steel Girder Design Chart 4 - Bolted Field Splice Design Chart 5 - Miscellaneous Steel Design Chart 6 - Bearing Design Chart 7 - Abutment and Wingwall Design Chart 8 - Pier Design Chart P - Pile Foundation Design Flowcharts Design Example for a Two-Span Bridge Flowcharting Conventions Start A process may have an entry point from more than one path. An arrowhead going into a process signifies an entry point.
Unique sequence identifier Process description Reference Process A Design Step # Chart # or AASHTO Reference Unless the process is a decision, there is only one exit point. A line going out of a process signifies an exit point. Commentary to provide additional information about the decision or process. Flowchart reference or article in AASHTO LRFD Bridge Design Specifications Supplemental Information No Decision Yes Process Design Step # Chart # or AASHTO Reference Go to Other Flowchart FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge Main Flowchart Start Design Step 1
General Information Chart 1 Design Step 2 Concrete Deck Design Chart 2 Design Step 3 Steel Girder Design Chart 3 Splices are generally required for girders that are too long to be transported to the bridge site in one piece. Yes No Are girder splices required? Design Step 4 Bolted Field Splice Design Chart 4 Design Step 5 Miscellaneous Steel Design Chart 5 Go to: A FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge Main Flowchart (Continued) A Design Step 6 Bearing Design Chart 6 Design Step 7 Abutment and Wingwall Design Chart 7 Design Step 8 Pier Design Chart 8 Design Step 9
Miscellaneous Design Chart 9 Design Step 10 Special Provisions and Cost Estimate Chart 10 Design Completed Note: Design Step P is used for pile foundation design for the abutments, wingwalls, or piers. FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge General Information Flowchart Chart 1 Start Start Design Step 1 General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 2 Design Step 1. 1 Obtain Design Criteria Design Step 3 No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing
Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Includes: Governing specifications, codes, and standards Design methodology Live load requirements Bridge width requirements Clearance requirements Bridge length requirements Material properties Future wearing surface Load modifiers Design Step 5 Design Step 6 Design Step 1. 2 Obtain Geometry Requirements Design Step 7 Includes: Horizontal curve data and alignment Vertical curve data and grades Design Step 8 Design Step 9 Yes Design Step 10
Does client require a Span Arrangement Study? No Includes: Select bridge type Determine span arrangement Determine substructure locations Compute span lengths Check horizontal clearance Design Step 1. 3 Perform Span Arrangement Study Design Step 1. 3 Select Bridge Type and Develop Span Arrangement Go to: A FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge General Information Flowchart (Continued) Chart 1 Start Design Step 1 General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 A Design Step 2 Design Step 3 No Are girder splices required?
Design Step 1. 4 Yes Obtain Geotechnical Recommendations Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 5 Includes: Boring logs Foundation type recommendations for all substructures Allowable bearing pressure Allowable settlement Overturning Sliding Allowable pile resistance (axial and lateral) Design Step 6 Design Step 7 Design Step 8 Yes Does client require a Type, Size and Location Study?
No Design Step 9 Design Step 10 Includes: Select steel girder types Girder spacing Approximate girder depth Check vertical clearance Design Step 1. 5 Perform Type, Size and Location Study Design Step 1. 5 Determine Optimum Girder Configuration Design Step 1. 6 Plan for Bridge Aesthetics S2. 5. 5 Considerations include: Function Proportion Harmony Order and rhythm Contrast and texture Light and shadow Return to Main Flowchart FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge Concrete Deck Design Flowchart Chart 2 Start Start General Information Chart 1 Design Step 1
Design Step 2. 1 Obtain Design Criteria Design Step 2 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 3 Includes: Girder spacing Number of girders Top and bottom cover Concrete strength Reinforcing steel strength Concrete density Future wearing surface Concrete parapet properties Applicable load combinations Resistance factors To compute the effective span length, S, assume a girder top flange width that is conservatively smaller than anticipated. The deck overhang region is required to be designed to have a resistance larger than the actual resistance of the concrete parapet.
Based on Design Steps 2. 3 and 2. 4 and based on client standards. No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 2. 2 Determine Minimum Slab Thickness S2. 5. 2. 6. 3 & S9. 7. 1. 1 Design Step 5 Design Step 6 Design Step 2. 3 Determine Minimum Overhang Thickness S13. 7. 3. 1. 2 Design Step 7 Design Step 8 Design Step 9 Design Step 2. Select Slab and Overhang Thickness Design Step 10 Yes Equivalent Strip Method? (S4. 6. 2) No Other deck design methods are presented in S9. 7. Design Step 2. 5 Compute Dead Load Effects S3. 5. 1 & S3. 4. 1 Includes moments for component dead load (DC) and wearing surface dead load (DW). Go to: A FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge Concrete Deck Design Flowchart (Continued) Chart 2 A Start General Information Chart 1 Design Step 2. 6 Compute Live Load Effects S3. 6. 1. 3 & S3. 4. 1 Design Step 1 Design Step 2 Concrete Deck Design Chart 2
Steel Girder Design Chart 3 Design Step 3 Design Step 2. 7 Compute Factored Positive and Negative Design Moments S4. 6. 2. 1 Considerations include: Dynamic load allowance (S3. 6. 2. 1) Multiple presence factor (S3. 6. 1. 1. 2) AASHTO moment table for equivalent strip method (STable A4. 1-1) No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed
Design Step 2. 8 Design for Positive Flexure in Deck S5. 7. 3 Resistance factor for flexure is found in S5. 5. 4. 2. 1. See also S5. 7. 2. 2 and S5. 7. 3. 3. 1. Generally, the bottom transverse reinforcement in the deck is checked for crack control. The live load negative moment is calculated at the design section to the right and to the left of each interior girder, and the extreme value is applicable to all design sections (S4. 6. 2. 1. 1). Generally, the top transverse reinforcement in the deck is checked for crack control. Design Step 5 Design Step 6 Design Step 2. 9 Design Step 7
Check for Positive Flexure Cracking under Service Limit State S5. 7. 3. 4 & S5. 7. 1 Design Step 8 Design Step 9 Design Step 2. 10 Design for Negative Flexure in Deck S4. 6. 2. 1 & S5. 7. 3 Design Step 10 Design Step 2. 11 Check for Negative Flexure Cracking under Service Limit State S5. 7. 3. 4 & S5. 7. 1 Design Step 2. 12 Design for Flexure in Deck Overhang S5. 7. 3. 4, S5. 7. 1 & SA13. 4 Go to: B FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge Concrete Deck Design Flowchart (Continued) Chart 2 For concrete parapets, the case of vertical collision never controls.
B Design Case 1 Design Overhang for Horizontal Vehicular Collision Force SA13. 4. 1 Design Case 2 Design Overhang for Vertical Collision Force SA13. 4. 1 Design Case 3 Design Overhang for Dead Load and Live Load SA13. 4. 1 Check at Case Inside Face 1A of Parapet Check at Case Design 1B Section in Overhang Check at Case Design 1C Section in First Span Check at Case Design 3A Section in Overhang Check at Case Design 3B Section in First Span As(Overhang) = maximum of the above five reinforcing steel areas Start General Information Chart 1 Design Step 1 Design Step 2 Concrete Deck Design Chart 2
Steel Girder Design Chart 3 Yes Design Step 3 As(Overhang) > As(Deck)? No No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Use As(Overhang) in overhang. Use As(Deck) in overhang. Check for Cracking in Overhang under Service Limit State S5. 7. 3. 4 & S5. 7. 1 The overhang reinforcing steel must satisfy both the overhang requirements and the deck requirements.
Design Step 5 Design Step 2. 13 Design Step 6 Does not control the design in most cases. Design Step 7 Design Step 8 Design Step 2. 14 Compute Overhang Cut-off Length Requirement S5. 11. 1. 2 Design Step 9 Design Step 10 Go to: C FHWA LRFD Steel Design Example 3 Flowcharts Design Example for a Two-Span Bridge Concrete Deck Design Flowchart (Continued) Chart 2 C Start General Information Chart 1 Design Step 2. 15 Compute Overhang Development Length S5. 11. 2 Appropriate correction factors must be included. Design Step 1 Design Step 2 Concrete Deck Design Chart 2 Steel Girder Design Chart 3
Design Step 2. 16 Design Bottom Longitudinal Distribution Reinforcement S9. 7. 3. 2 Design Step 3 Compute Effective Span Length, S, in accordance with S9. 7. 2. 3. Based on temperature and shrinkage reinforcement requirements. No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 2. 17 Design Top Longitudinal Distribution Reinforcement S5. 0. 8. 2 Design Step 5 Design Step 6 Design Step 2. 18 Design Longitudinal Reinforcement over Piers Design Step 7 Design Step 8 Design Step 9 Yes Continuous steel girders? No Design Step 10 For simple span precast girders made continuous for live load, design top longitudinal reinforcement over piers according to S5. 14. 1. 2. 7. For continuous steel girders, design top longitudinal reinforcement over piers according to S6. 10. 3. 7. Design Step 2. 19 Draw Schematic of Final Concrete Deck Design Return to Main Flowchart FHWA LRFD Steel Design Example 4 Flowcharts
Design Example for a Two-Span Bridge Steel Girder Design Flowchart Chart 3 Start Includes project specific design criteria (such as span configuration, girder configuration, initial spacing of cross frames, material properties, and deck slab design) and design criteria from AASHTO (such as load factors, resistance factors, and multiple presence factors). Start General Information Chart 1 Concrete Deck Design Chart 2 Design Step 1 Design Step 3. 1 Obtain Design Criteria Design Step 2 Design Step 3 Steel Girder Design Chart 3 No Are girder splices required? Yes Design Step 4
Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed A Design Step 3. 2 Select Trial Girder Section Design Step 5 Design Step 6 Design Step 7 Design Step 8 Design Step 9 Yes Composite section? No Considerations include: Sequence of loading (S6. 10. 3. 1. 1a) Effective flange width (S4. 6. 2. 6) Design Step 10 Design Step 3. 3 Compute Section Properties for Composite Girder S6. 10. 3. 1
Design Step 3. 3 Compute Section Properties for Noncomposite Girder S6. 10. 3. 3 Go to: B FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge Steel Girder Design Flowchart (Continued) Chart 3 B Includes component dead load (DC) and wearing surface dead load (DW). Start General Information Chart 1 Concrete Deck Design Chart 2 Design Step 3. 4 Compute Dead Load Effects S3. 5. 1 Design Step 1 Design Step 2 Design Step 3 Steel Girder Design Chart 3 Design Step 3. 5 Compute Live Load Effects S3. 6. 1 Considerations include: LL distribution factors (S4. . 2. 2) Dynamic load allowance (S3. 6. 2. 1) Includes load factors and load combinations for strength, service, and fatigue limit states. Considerations include: General proportions (6. 10. 2. 1) Web slenderness (6. 10. 2. 2) Flange proportions (6. 10. 2. 3) Go to: A No Are girder splices required? Yes Design Step 4 Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 3. Combine Load Effects S3. 4. 1 Design Step 5 Design Step 6 Design Step 7 Design Step 3. 7 Check Section Proportion Limits S6. 10. 2 Design Step 8 Design Step 9 Design Step 10 Are section proportions adequate? Yes Go to: C No FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Flowchart (Continued) Chart 3 Design Step 1 Design Step 2 C Design Step 3 Steel Girder Design Chart 3 No Are girder splices required? Yes No Composite section? Yes Design Step 4
Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 5 Design Step 3. 8 Compute Plastic Moment Capacity S6. 10. 3. 1. 3 & Appendix A6. 1 Considerations include: Web slenderness Compression flange slenderness (N only) Compression flange bracing (N only) Ductility (P only) Plastic forces and neutral axis (P only) Design for Flexure Strength Limit State S6. 10. (Flexural resistance in terms of stress) Considerations include: Computations at end panels and interior panels for stiffened or partially stiffened girders Computation of shear resistance Check D/tw for shear Check web fatigue stress (S6. 10. 6. 4) Check handling requirements Check nominal shear resistance for constructability (S6. 10. 3. 2. 3) Design Step 6 Design Step 7 Design Step 8 Design Step 9 D Design Step 3. 9 Determine if Section is Compact or Noncompact S6. 10. 4. 1 Design Step 10 Yes Design for Flexure Strength Limit State S6. 10. 4 (Flexural resistance in terms of moment) Compact section? No Design Step 3. 10 Design Step 3. 0 Design Step 3. 11 Design for Shear S6. 10. 7 Note: P denotes Positive Flexure. N denotes Negative Flexure. Go to: E FHWA LRFD Steel Design Example 3 Flowcharts Design Example for a Two-Span Bridge Steel Girder Design Flowchart (Continued) Chart 3 E No Transverse intermediate stiffeners? If no stiffeners are used, then the girder must be designed for shear based on the use of an unstiffened web. Design includes: Select single-plate or double-plate Compute projecting width, moment of inertia, and area Check slenderness requirements (S6. 10. 8. 1. 2) Check stiffness requirements (S6. 10. 8. 1. 3) Check strength requirements (S6. 0. 8. 1. 4) If no longitudinal stiffeners are used, then the girder must be designed for shear based on the use of either an unstiffened or a transversely stiffened web, as applicable. Design includes: Determine required locations Select stiffener sizes Compute projecting width and moment of inertia Check slenderness requirements Check stiffness requirements Yes Start General Information Chart 1 Concrete Deck Design Chart 2 Design Step 1 Design Step 3. 12 Design Transverse Intermediate Stiffeners S6. 10. 8. 1 Design Step 2 Design Step 3 Steel Girder Design Chart 3 No Are girder splices required? Yes Design Step 4
Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed No Longitudinal stiffeners? Design Step 5 Design Step 6 Yes Design Step 7 Design Step 8 Design Step 3. 13 Design Longitudinal Stiffeners S6. 10. 8. 3 Design Step 9 Design Step 10 Go to: F FHWA LRFD Steel Design Example 4 Flowcharts Design Example for a Two-Span Bridge Steel Girder Design Flowchart (Continued) Chart 3 F No Is stiffened web most cost effective? Yes Use unstiffened web in steel girder design.
Use stiffened web in steel girder design. Start General Information Chart 1 Concrete Deck Design Chart 2 Design Step 1 Design Step 2 Design Step 3. 14 Design Step 3 Steel Girder Design Chart 3 Design for Flexure Fatigue and Fracture Limit State S6. 6. 1. 2 & S6. 10. 6 No Are girder splices required? Yes Check: Fatigue load (S3. 6. 1. 4) Load-induced fatigue (S6. 6. 1. 2) Fatigue requirements for webs (S6. 10. 6) Distortion induced fatigue Fracture Compute: Live load deflection (optional) (S2. 5. 2. 6. 2) Permanent deflection (S6. 10. 5) Check: Web slenderness Compression flange slenderness Compression flange bracing Shear
Design Step 4 Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 5 Design Step 3. 15 Design for Flexure Service Limit State S2. 5. 2. 6. 2 & S6. 10. 5 Design Step 6 Design Step 7 Design Step 8 Design Step 3. 16 Design for Flexure Constructibility Check S6. 10. 3. 2 Design Step 9 Design Step 10 Go to: G FHWA LRFD Steel Design Example 5 Flowcharts Design Example for a Two-Span Bridge Steel Girder Design Flowchart (Continued) Chart 3 G
Start General Information Chart 1 Concrete Deck Design Chart 2 Design Step 3. 17 Check Wind Effects on Girder Flanges S6. 10. 3. 5 Design Step 1 Refer to Design Step 3. 9 for determination of compact or noncompact section. Design Step 2 Design Step 3 Steel Girder Design Chart 3 No Are girder splices required? Yes Design Step 4 Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Have all positive and negative flexure design sections been checked?
No Go to: D (and repeat flexural checks) Design Step 5 Yes Design Step 6 Design Step 7 Design Step 8 Were all specification checks satisfied, and is the girder optimized? No Go to: A Design Step 9 Design Step 10 Yes Design Step 3. 18 Draw Schematic of Final Steel Girder Design Return to Main Flowchart FHWA LRFD Steel Design Example 6 Flowcharts Design Example for a Two-Span Bridge Bolted Field Splice Design Flowchart Chart 4 Start Includes: Splice location Girder section properties Material and bolt properties Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3
Design Step 4. 1 Obtain Design Criteria Design Step 1 Design Step 2 Design Step 3 Design Step 4. 2 Select Girder Section as Basis for Field Splice Design S6. 13. 6. 1. 1 Design bolted field splice based on the smaller adjacent girder section (S6. 13. 6. 1. 1). No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Left Design Step 5 Which adjacent girder section is smaller? Right
Design Step 6 Design Step 7 Design Step 8 Design bolted field splice based on left adjacent girder section properties. Design bolted field splice based on right adjacent girder section properties. Design Step 9 Design Step 10 Design Step 4. 3 Compute Flange Splice Design Loads 6. 13. 6. 1. 4c Includes: Girder moments Strength stresses and forces Service stresses and forces Fatigue stresses and forces Controlling and noncontrolling flange Construction moments and shears Go to: A FHWA LRFD Steel Design Example 1 Flowcharts Design Example for a Two-Span Bridge Bolted Field Splice Design Flowchart (Continued) Chart 4
Check: Yielding / fracture of splice plates Block shear rupture resistance (S6. 13. 4) Shear of flange bolts Slip resistance Minimum spacing (6. 13. 2. 6. 1) Maximum spacing for sealing (6. 13. 2. 6. 2) Maximum pitch for stitch bolts (6. 13. 2. 6. 3) Edge distance (6. 13. 2. 6. 6) Bearing at bolt holes (6. 13. 2. 9) Fatigue of splice plates (6. 6. 1) Control of permanent deflection (6. 10. 5. 2) A Design Step 4. 4 Design Bottom Flange Splice 6. 13. 6. 1. 4c Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 1 Design Step 2 Design Step 3 No Are girder splices required?
Design Step 4. 5 Yes Design Top Flange Splice S6. 13. 6. 1. 4c Check: Refer to Design Step 4. 4 Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 5 Design Step 6 Design Step 4. 6 Design Step 7 Compute Web Splice Design Loads S6. 13. 6. 1. 4b Design Step 8 Check: Girder shear forces Shear resistance for strength Web moments and horizontal force resultants for strength, service and fatigue
Design Step 9 Design Step 10 Go to: B FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge Bolted Field Splice Design Flowchart (Continued) Chart 4 B Check: Bolt shear strength Shear yielding of splice plate (6. 13. 5. 3) Fracture on the net section (6. 13. 4) Block shear rupture resistance (6. 13. 4) Flexural yielding of splice plates Bearing resistance (6. 13. 2. 9) Fatigue of splice plates (6. 6. 1. 2. 2) Both the top and bottom flange splices must be designed, and they are designed using the same procedures.
Are both the top and bottom flange splice designs completed? No Go to: A Design Step 4. 7 Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 1 Design Web Splice S6. 13. 6. 1. 4b Design Step 2 Design Step 3 No Are girder splices required? Yes Design Step 4 Bolted Field Splice Design Chart 4 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 5 Design Step 6 Design Step 7
Yes Design Step 8 Design Step 9 Design Step 10 Do all bolt patterns satisfy all specifications? No Go to: A Yes Design Step 4. 8 Draw Schematic of Final Bolted Field Splice Design Return to Main Flowchart FHWA LRFD Steel Design Example 3 Flowcharts Design Example for a Two-Span Bridge Miscellaneous Steel Design Flowchart Chart 5 Start No Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Composite section? For a composite section, shear connectors are required to develop composite action between the steel girder and the concrete deck.
Design includes: Shear connector details (type, length, diameter, transverse spacing, cover, penetration, and pitch) Design for fatigue resistance (S6. 10. 7. 4. 2) Check for strength limit state (positive and negative flexure regions) (S6. 10. 7. 4. 4) Design includes: Determine required locations (abutments and interior supports) Select stiffener sizes and arrangement Compute projecting width and effective section Check bearing resistance Check axial resistance Check slenderness requirements (S6. 9. 3) Check nominal compressive resistance (S6. 9. 2. 1 and S6. 9. 4. ) Design Step 1 Yes Design Step 2 Design Step 3 No Are girder splices required? Design Step 5. 1 Yes Design Shear Connectors S6. 10. 7. 4 Design Step 4 Bolted Field Splice Chart 4 Design Step 5 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 6 Design Step 7 Design Step 8 Design Step 9 Design Step 5. 2 Design Bearing Stiffeners S6. 10. 8. 2 Design Step 10 Go to: A FHWA LRFD Steel Design Example 1
Flowcharts Design Example for a Two-Span Bridge Miscellaneous Steel Design Flowchart (Continued) Chart 5 A Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 1 Design Design Welded Connections Step 5. 3 S6. 13. 3 Design Step 2 Design Step 3 Design includes: Determine required locations Determine weld type Compute factored resistance (tension, compression, and shear) Check effective area (required and minimum) Check minimum effective length requirements To determine the need for diaphragms or cross frames, refer to S6. . 4. 1. No Are girder splices required? Yes Design Step 4 Bolted Field Splice Chart 4 No Are diaphragms or cross frames required? Design Step 5 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design Step 6 Yes Design Step 7 Design Step 8 Design Step 9 Design Step 10 Design Step 5. 4 Design Cross-frames S6. 7. 4 Go to: B
Design includes: Obtain required locations and spacing (determined during girder design) Design cross frames over supports and intermediate cross frames Check transfer of lateral wind loads Check stability of girder compression flanges during erection Check distribution of vertical loads applied to structure Design cross frame members Design connections FHWA LRFD Steel Design Example 2 Flowcharts Design Example for a Two-Span Bridge Miscellaneous Steel Design Flowchart (Continued) Chart 5 B Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 1 No Is lateral bracing required?
To determine the need for lateral bracing, refer to S6. 7. 5. 1. Design Step 2 Design Step 3 Yes No Are girder splices required? Yes Design Step 4 Bolted Field Splice Chart 4 Design Step 5. 5 Design Lateral Bracing S6. 7. 5 Design Step 5 Miscellaneous Steel Design Chart 5 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed Design includes: Check transfer of lateral wind loads Check control of deformation during erection and placement of deck Design bracing members Design connections Design Step 6
Design Step 7 Design Step 8 Design Step 9 Design Step 5. 6 Compute Girder Camber S6. 7. 2 Design Step 10 Return to Main Flowchart Compute the following camber components: Camber due to dead load of structural steel Camber due to dead load of concrete deck Camber due to superimposed dead load Camber due to vertical profile Residual camber (if any) Total camber FHWA LRFD Steel Design Example 3 Flowcharts Design Example for a Two-Span Bridge Bearing Design Flowchart Chart 6 Start Includes: Movement (longitudinal and transverse) Rotation (longitudinal, transverse, and vertical) Loads (longitudinal, transverse, and vertical)
Start General Information Chart 1 Concrete Deck Design Chart 2 Steel Girder Design Chart 3 Design Step 6. 1 Obtain Design Criteria Design Step 1 Design Step 2 Design Step 3 No Are girder splices required? Yes Design Step 6. 2 Select Optimum Bearing Type S14. 6. 2 See list of bearing types and selection criteria in AASHTO Table 14. 6. 2-1. Design Step 4 Bolted Field Splice Chart 4 Miscellaneous Steel Design Chart 5 Design Step 5 Design Step 6 Bearing Design Chart 6 Abutment and Wingwall Design Chart 7 Pier Design Chart 8 Miscellaneous Design Chart 9 Special Provisions and Cost Estimate Chart 10 Design Completed
Steelreinforced elastomeric bearing? No Design selected bearing type in accordance with S14. 7. Includes: Pad length Pad width Thickness of elastomeric layers Number of steel reinforcement layers Thickness of steel reinforcement layers Edge distance Material properties Method A usually results in a bearing with a lower capacity than Method B. However, Method B requires additional testing and quality control (SC14. 7. 5. 1). Note: Method A is described in S14. 7. 6. Method B is described in S14. 7. 5. Design Step 7 Yes Design Step 8 Design Step 9 A
