Increasing Girder Elastic Buckling Strength Using Split Pipe Bearing Stiffeners

Abstract

Warping restraining devices can result in substantial improvements in the girder elastic buckling capacity; however, calculating this increase can be complex. This paper presents a simplified method to evaluate the increase in elastic buckling strength and corresponding unbraced length due to improved warping restraint provided by split pipe stiffeners located at the ends of doubly symmetric W-shapes. The solution is based on analytical studies and results from a finite-element parametric study validated using large-scale laboratory tests. The laboratory tests include specimens exposed to concentrated loads with split pipe warp-restraining devices and others with standard plate stiffeners. The proposed analytic method is based on uniform moment and shows that warping restraint can increase the elastic buckling capacity of a girder by 30–100%. The improved warping stiffness can result in increases in the unbraced length in the range of 20–35% compared with systems with plate stiffeners.