Local Mechanical Behaviors of Steel Box Girder During Skew Incremental Launching

In the process of incremental launching construction, deviation error will pose a threat to the bridge safety. Two adverse conditions were selected for numerical analysis to investigate the steel box girder local stress during skew incremental launching and the effects of deviation error in the process. The maximum stress of the two working conditions is similar to that of the web when the skewed and cantilevered conditions are 275.2 MPa and 195.0 MPa, respectively. The top plates stress is 211.7 MPa under skewed condition and 73.2 MPa under cantilevered condition. There is a great difference between the two conditions. Attention should be paid to the change of top plates stress in the actual launching process. Among the three launching deviations, the longitudinal deviation presents the least influence on the girder. The vertical deviation depicts the greatest influence, which will lead to a significant increase in the local stress of the steel box girder. When the vertical displacement reaches 10 cm, the web stress reaches almost four times of the normal condition. Thus, for actual incremental launching, the synchronization of vertical launching shall be ensured as far as possible to reduce the risk during incremental launching.