Behavior of Trapezoidal Box Girders with Skewed Supports;Research rept. (Final) (Sep 00-Aug 03)

摘要

Although there are significant structural advantages in the completed box girder bridge, during construction box girders require a number of bracing systems to improve their torsional stiffness and maintain stability. Typical bracing systems for steel box girders include internal and external cross-frames and also a top flange lateral truss. A previous TxDOT study, Project 0-1395 Field and Computational Studies of Steel Trapezoidal Box Girders, resulted in design expression for the bracing systems. Helwig and Fan (2000) presented design expressions to predict the forces in the top lateral truss and internal K-frames. However, the effects of external intermediate cross-frames and support skew were not considered in the development of the bracing design expressions in this previous study. The purpose of this investigation is to improve the understanding of trapezoidal box girders with skewed supports. The impact of external K-frames on the behavior of the internal K-frames and top lateral truss was also studied. Modifications to the design equations for box girder bracing are recommended in this report, as well as a design methodology for the external K-frames. Methods of analysis are also discussed and simplified methods are presented for girders with skewed supports.