Residual Deformation Analysis for Inelastic Bridge Rating

A new bridge rating method, residual deformation analysis (RDA), is presented. RDA is a method for assessing the residual moments and deformations that are set up in a bridge beam that has been loaded into its inelastic resistance range. RDA combines classical elastic conjugate beam theory with empirically formulated moment‐versus‐rotation relationships for both midspan inelastic positive moment and interior support inelastic negative moment hinging. The RDA method will allow bridge engineers to more easily and systematically incorporate the automoment concept of the American Association of State Highway and Transportation Officials (AASHTO) alternate load factor design (ALFD) method into an inelastic bridge analysis. The RDA techniques developed for inelastic bridge rating are both an extension and a refinement of the analysis procedures given as the ALFD method. Bridge rating by RDA follows a straightforward procedure that will allow bridge engineers to compute higher‐rated load capacities of existing bridge structures, thus providing the potential of avoiding the unnecessary posting of many bridge structures that might otherwise rate below minimum legal load levels.