Wood Bridge Design Using AASHTO LRFD Specifications

A nationwide project to develop a load and resistance factor (LRFD) design edition of the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges began in late 1988 and is expected to be completed in 1993. An integral part of this process was to develop consistent LRFD design specifications for all highway bridge construction materials. Since LRFD specifications for wood structures had not previously been published this presented a considerable challenge to the wood industry. It also presented a unique opportunity to completely update the AASHTO design requirements for wood structures which have traditionally lagged behind contemporary wood design methodologies. The result is a state of the art approach to the design of wood bridges incorporating several significant departures from current allowable stress design (ASD) practice. This paper presents an overview of the AASHTO LRFD Specifications for Highway Structures as they apply to timber structures.