Performance of the Transverse Connectivity in Simply Supported Girder Bridges and Its Strengthening Strategy

A critical problem in evaluating the structural behavior of simply supported girder bridges is the performance of the transverse connectivity of girders. Traditional structural calibration factors, which are based on loading test results, are only capable of evaluating the load-bearing capacity of girders. To resolve the difficulty in evaluating the transverse connectivity performance of existing simply supported girder bridges, two parameters Pn and Pm were proposed based on the loading tests results of 65 simply supported concrete girder bridges. Moreover, threshold values for these two parameters were specified according to statistical analysis of loading tests results: when Pn≤0.3 or Pm≤1.0, the bridges perform well as a complete structure in the transverse direction, and only minor repairs are needed; when Pn>0.3 or Pm>1.0, the bridges perform poorly in the transverse direction and necessary repairing measures should be taken. Based on the data of the two evaluation parameters of surveyed bridges, a detailed strengthening strategy was established and successfully implemented in 13 field projects. According to the strengthening strategy, the following steps are to be conducted: (1) remove the damage zones in bridges, (2) rebar embedding in hinge joints, (3) install reinforcing steel grids, and (4) concrete repair. Comparative tests were made on bridges before and after the strengthening process. The results confirmed the feasibility and efficiency of the proposed strategy.