LRFD Steel Design - Pages

1 lrfd Steel Design AASHTO lrfd Bridge Design Specifications Slide Shows Created July 2007. This material is copyrighted by The University of Cincinnati and Dr. James A Swanson. It may not be reproduced, distributed, sold, or stored by any means, electrical or mechanical, without the expressed written consent of The University of Cincinnati and Dr. James A Swanson. July 31, 2007. lrfd Steel Design AASHTO lrfd Bridge Design Specification Slide Shows Review of Loads and Analysis ..1. Scope, Materials, and Limit Fatigue and Fracture ..45. Tension Compression Bending Members - Flexural Bending Members - Flexural Bending Members - Shear Web Strength and Connections and Splices ..213. Cost Effective Design of Steel Bridges ..261. James A Swanson Associate Professor University of Cincinnati Dept of Civil & Env. engineering 765 Baldwin Hall Cincinnati, OH 45221-0071.

2 Ph: (513) 556-3774. Fx: (513) 556-2599. Review of Loads and Analysis AASHTO lrfd . Review of Loads and Analysis James A Swanson AASHTO- lrfd Specification, 4th Ed., 2007. References Bridge engineering handbook , Wai-Faf Chen and Lian Duan, 1999, CRC Press (ISBN: 0-8493-7434-0). Four lrfd Design Examples of Steel Highway Bridges, Vol. II, Chapter 1A. Highway Structures Design handbook , Published by American Iron and Steel Institute in cooperation with HDR engineering , Inc. Available at Design of Highway Bridges, 2nd Ed. Richard Barker and Jay Puckett, 2007, Wiley &. Sons (ISBN: 0-471-69758-3). AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #2. -- 1 -- Review of Loads and Analysis References AASHTO Web Site: Load and Resistance Factor Design for Highway Bridges, Participant Notebook, Available from the AASHTO web site.

3 AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #3. References AISC / National Steel Bridge Alliance Web Site: org/. Steel Bridge Design handbook . AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #4. -- 2 -- Review of Loads and Analysis References Steel Structures Design and Behavior, 4th Ed. Charles G. Salmon and John E. Johnson, 1996, Harper Collins Guide to Stability Design Criteria for Metal Structures, 5th Ed. Edited by Theodore V. Galambos, 1998, John Wiley & Sons, Available at Design of Steel Structures, 3rd Ed., Edwin H. Gaylord, Charles N. Gaylord, and James E. Stallmeyer, 1992, McGraw-Hill AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #5. References AASHTO Standard Specification for Highway Bridges, 17th Edition, 1997, 2003.

4 AASHTO lrfd Bridge Design Specifications, 4th Edition, 2007. AASHTO Guide Specification for Distribution of Loads for Highway Bridges . AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #6. -- 3 -- Review of Loads and Analysis Philosophies of Design lrfd : Load & Resistance Factor Design For Safety: Q R n Q - Load Effect R - Component Resistance - Load Factor - Resistance Factor The lrfd philosophy provides a more uniform, systematic, and rational approach to the selection of load factors and resistance factors than LFD. Chen & Duan AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #7. Philosophies of Design - lrfd Fundamentals Reliability Index: ASD / LFD Bridge Designs lrfd Bridge Designs (Expected). 5 5. 4 4. Reliability Index Reliability Index 3 3. 2 2.

5 1 1. 0 0. 0 27 54 81 108 180 0 27 54 81 108 180. Span Length (ft) Span Length (ft). Chen & Duan AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #8. -- 4 -- Review of Loads and Analysis AASHTO- lrfd Specification Contents 1. Introduction 8. Wood Structures 2. General Design and Location 9. Decks and Deck Systems Features 10. Foundations 3. Loads and Load Factors 11. Abutments, Piers, and Walls 4. structural Analysis and 12. Buried Structures and Tunnel Evaluation Liners 5. Concrete Structures 13. Railings 6. Steel Structures 14. Joints and Bearings 7. Aluminum Structures 15. Index AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #9. Chapter 1 Introduction : Limit States Service: Deals with restrictions on stress, deformation, and crack width under regular service conditions.

6 Intended to ensure that the bridge performs acceptably during its Design life. Strength: Intended to ensure that strength and stability are provided to resist statistically significant load combinations that a bridge will experience during its Design life. Extensive distress and structural damage may occur at strength limit state conditions, but overall structural integrity is expected to be maintained. Extreme Event: Intended to ensure structural survival of a bridge during an earthquake, vehicle collision, ice flow, or foundation scour. Fatigue: Deals with restrictions on stress range under regular service conditions reflecting the number of expected cycles. Pgs ; Chen & Duan AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #10. -- 5 -- Review of Loads and Analysis Chapter 1 Introduction : Limit States Q = i i Qi ( ).

7 I - Load Factor Qi - Load Effect i - Load Modifier When the maximum value of i is appropriate i = D R I ( ). When the minimum value of i is appropriate 1. i = ( ). D R I. Pg AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #11. Chapter 1 Introduction : Limit States - Load Modifiers Applicable only to the Strength Limit State D Ductility Factor: D = for nonductile members D = for conventional designs and details complying with specifications D = for components for which additional ductility measures have been taken R Redundancy Factor: R = for nonredundant members R = for conventional levels of redundancy R = for exceptional levels of redundancy I Operational Importance: I = for important bridges I = for typical bridges I = for relatively less important bridges These modifiers are applied at the element level, not the entire structure.

8 Pgs. ; Chen & Duan AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #12. -- 6 -- Review of Loads and Analysis - Load Factors and Combinations : ODOT Recommended Load Modifiers For the Strength Limit States D Ductility Factor: Use a ductility load modifier of D = for all strength limit states R Redundancy Factor: Use R = for non-redundant members Use R = for redundant members Bridges with 3 or fewer girders should be considered non-redundant.. Bridges with 4 girders with a spacing of 12' or more should be considered non- redundant.. Bridges with 4 girders with a spacing of less than 12' should be considered redundant.. Bridge with 5 or more girders should be considered redundant.. AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #13. - Load Factors and Combinations : ODOT Recommended Load Modifiers For the Strength Limit States R Redundancy Factor: Use R = for non-redundant members Use R = for redundant members Single and two column piers should be considered non-redundant.

9 Cap and column piers with three or more columns should be considered redundant. T-type piers with a stem height to width ratio of 3-1 or greater should be considered non-redundant. For information on other substructure types, refer to NCHRP Report 458. Redundancy in Highway Bridge Substructures. R does NOT apply to foundations. Foundation redundancy is included in the resistance factor. AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #14. -- 7 -- Review of Loads and Analysis - Load Factors and Combinations : ODOT Recommended Load Modifiers For the Strength Limit States I Operational Importance: In General, use I = unless one of the following applies Use I = if any of the following apply Design ADT 60,000. Detour length 50 miles Any span length 500'. Use I = if both of the following apply Design ADT 400.

10 Detour length 10 miles Detour length applies to the shortest, emergency detour route. AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #15. AASHTO- lrfd . Chapter 3: Loads and Load Factors James A Swanson AASHTO- lrfd Specification, 4th Ed., 2007. -- 8 -- Review of Loads and Analysis - Loads and Load Factors : Load Factors and Load Combinations Permanent Loads DD - Downdrag EH - Horizontal Earth Pressure DC - structural EL - Locked-In Force Components and Effects Including Attachments Pretension DW - Wearing Surfaces ES - Earth Surcharge and Utilities Load EV - Vertical Pressure of Earth Fill Pg AASHTO- lrfd 2007. ODOT Short Course Created July 2007 Review of Loads: Slide #17. - Loads and Load Factors : Load Factors and Load Combinations Transient Loads BR Veh. Braking Force LS - Live Load Surcharge CE Veh.