Review of Bridge Design and Evaluation: LRFD and LRFR by Gongkang Fu

The book focuses on AASHTO LRFD bridge design and load and resistance factor rating (LRFR) bridge evaluation of superstructure, bearings, and substructure of concrete and steel bridges.

The book serves as a textbook to introduce students, engineers, and nonengineers to the design and evaluation of highway bridges in accordance with the AASHTO LRFD bridge design specifications and the AASHTO Manual for bridge evaluation, with numerous worked examples to illustrate the applications of the AASHTO specifications.

Dr. Gongkang Fu is Professor of Civil Engineering and Chairman of the Department of Civil, Architectural, and Environmental Engineering at Illinois Institute of Technology. He has taught bridge design and evaluation at Wayne State University and the Illinois Institute of Technology for 16 years. He was Head of Structures Research with the New York State DOT for 7 years, and has worked on research and design projects for the Federal Highway Administration (FHWA) and the DOTs of California, Georgia, New York, Michigan, and Ohio.

This is a welcome and timely introductory textbook on the AASHTO LRFD bridge design specifications (LRFD), 6th Edition, and the AASHTO Manual for bridge evaluation, 2nd Edition. Beginning October 1, 2007, the United States has been using LRFD in bridge design. Starting in June 2010, the United States has been using LRFR for load rating of bridges designed in accordance with LRFD. This textbook will prepare students and prospective bridge engineers with sound and fundamental knowledge in LRFD and LRFR. When they join the United States’ or a consultant’s bridge engineering workforce, they will quickly learn the organizations’ bridge engineering practices and gain hands-on experience in the design and evaluation of highway bridges.

This textbook is very good for an undergraduate and graduate course on highway bridge design and evaluation. This textbook is also a very good reference for bridge engineers who have not taken a formal classroom course on bridge design or evaluation using LRFD and LRFR. In the study of LRFD and LRFR using this textbook, it is preferable, but not required, to have a copy of AASHTO LRFD bridge design specifications, 6th Edition, and the AASHTO Manual of bridge evaluation, 2nd Edition. The commentaries in these specifications provide a very good background and reasons for the specifications. The textbook provides references to the relevant sections of the AASHTO specifications for further study and understanding.

This book has seven chapters. Chapter 1 gives a very good introduction to bridge types and discusses the design and evaluation methods covered by the AASHTO specifications. Chapter 2 is a very important chapter for a full understanding and appreciation of the modern probability-based LRFD and LRFR specifications. The author does a very good job in simply and clearly explaining the philosophy, benefits, and applicability of the specifications. This chapter introduces the basic LRFD equation that four limit states must satisfy. The LRFD defines four limit states that must be satisfied to achieve safety, serviceability, constructability, inspectability, economy, and aesthetics. The four limit states are

Additionally, Chapter 2 covers the concepts of structural reliability used in calibrating the design and evaluation to provide a high and uniform level of safety. Chapter 3 gives detailed discussions on the loads and load combinations used in design and evaluation. This chapter introduces the LRFD HL-93 live load model. The live load model consists of a combination of design truck or design tandem and design lane load. The design truck is the familiar AASHTO HS20 truck. The design tandem is a tandem of two equal axles, each 111 kN (25 kips) and spaced at 1.22 m (4 ft). The design lane load is the familiar AASHTO uniform load of 9.34 kN/m (640 lb/ft). The design truck and design lane load or design tandem and design lane load are combined to obtain the live load effects. Impact or dynamic effect of the live load is applied to the design truck or tandem only. The impact or dynamic effect does not apply to the design lane load. Other permanent and transient loads are also discussed. Several worked examples are included in this chapter to illustrate the application of loads and load combinations in the design of deck slabs, abutment walls, and beams.

In the next three chapters, the author treats a bridge as three subsystems, namely, superstructure, bearings, and substructure. A chapter is devoted to each subsystem, with design examples on the various components that make up the subsystem. References for further reading and exercise problems for the students to solve for better understanding of the specifications are given at the end of each chapter. Specifically, Chapter 4 is devoted to the design of the superstructures of various types of concrete and steel bridges and the various deck systems used in current practice, with detailed explanations and design examples of the most commonly used RC slab system. Chapter 5 is devoted to the design of bridge bearings, which are important components for short- and long-term performance of a bridge, and Chapter 6 is devoted to the design of the substructure, including the piers, abutments, and foundations.

The last chapter, Chapter 7, deals with bridge inspection, condition rating, and load rating, including fatigue evaluation of steel members. Many worked examples are included to illustrate the application of the AASHTO Manual for bridge evaluation. This is a very important chapter for students of bridge engineering and aspiring bridge engineers. Bridge owners of highway bridges on all public roads are required to perform regular bridge safety inspection, condition rating, and load rating in compliance with the National Bridge Inspection Standards (NBIS). The integration of this chapter in this book reflects very well on the educational and practical experience of the author in working with several state DOTs in the research, design, and evaluation of bridge projects.

This will be a very good book to learn about or teach the design and evaluation of bridge superstructures, bearings, and substructures using the AASHTO LRFD and LRFR. It is written simply and concisely, with clear explanations, formulations, and worked examples in customary U.S. units, consistent with the AASHTO specifications, and it meets the demand in LRFD and LRFR knowledge and skill in bridge engineering offices. Table 1 may be used to convert U.S. customary units to SI units.