Why the AASHTO Load and Resistance Factor Design Specifications?

Abstract

The use of the new AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications offers many advantages. Major changes to and benefits of these specifications are discussed. The AASHTO LRFD is based on new developments in bridge engineering, sound principles, and logical approaches to ensure constructibility, safety, serviceability, inspectability, economy, and aesthetics. LRFD incorporates the best of working stress design and load factor design familiar to practicing bridge engineers. It is a comprehensive, well-organized, and practical specification, with commentary to provide explanation and background information. New bridges designed according to LRFD have the inherent advantage of a more uniform level of safety, resulting in low life-cycle cost. LRFD allows the use of advanced methods in design and analysis. It provides flexibility for maintaining good and successful engineering practices or customizing load and resistance factors to meet the demands of a project. There are many good reasons and motivations to use LRFD. College classes, training courses, design examples, workshops, and computer software are now available to ease the implementation of AASHTO LRFD.