InTrans / Aug 14, 2018

Load and resistance factor design code for wood bridges

The development of a load and resistance factor design (LRFD) edition of AASHTO‰Ûªs Standard Specifications for Highway Bridges is complete. A part of this effort involved the development of LRFD provisions for wood bridges. These new specifications include numerous changes and several significant departures from current allowable stress design practices for wood bridges. The live load model is based on the statistical analysis of the actual traffic data. The design load is a superposition of the traditional HS20 truck and lane loading. Dynamic load is applied to wooden components of the superstructure. Strength of material is based on the nominal values derived from in-grade tests, specified for wet-use conditions and 2-month live load duration. The resistance factors are determined consistently for all the limit states considered. The major changes in
the approach to summarize the design provisions are presented.