Brace Effectiveness of Cross-frame Layout and Connection Design on Skewed Steel Bridges During Construction

Abstract

The Kansas Department of Transportation (KDOT)'s current design practice is to align cross-frames parallel to the skew angle to avoid problems associated with fit-up during erection. The American Association of State Highway and Transportation Officials (AASHTO) provisions for bridges with skew angle greater than 20 degrees are based on the assumption that cross-frames are oriented perpendicular to the girder line. There is a potentially significant discrepancy between assumptions implicit in the AASHTO Specifications and bridges that are designed with cross-frames placed parallel to the skew for skew angles between 20 and 40 degrees. An analytical approach was chosen to study the effects of cross-frame orientation, spacing, skew angle, and connection design upon flange stresses, bridge stability, and cross-frame stresses.