Localized Stresses in a Post-Tensioned Steel Girder Web-Field Verification. Part 1. Text, Tables and Figures

摘要

A steel plate girder and concrete deck slab bridge (Yuba Pass Bridge and Overhead) has been rehabilitated by placement of a concrete deck overlay, addition of lower steel flanges and post-tensioning of girder webs. A previous Caltrans report and TRB article discussed purely theoretical, pre-construction analyses with FINPLA and STRUDL made because of concern over potential large web stresses due to post-tensioning forces. A second phase study has been performed to modify previous analyses for assumed full clamping of post-tensioning brackets to webs and to verify analytical procedures by installation of SR-4 rosettes in the vicinity of a bracket on one girder web and monitoring during post-tensioning. Assumptions included full composite and non-composite deck contributions, and uniform and non-uniform bracket loadings. Theoretical/experimental correlations were good for longitudinal strains and minor principal stresses, less encouraging for vertical strains and major principal stresses. Correlations were improved when some composite.action by the physically non-composite deck and for non-uniform bracket loading was assumed. Theoretical stresses were significantly reduced by assumption of full bracket clamping.