Local Buckling of Pultruded FRP Beams-Analysis and Design

Abstract

An investigation of the local compression flange buckling and failure of pultruded fiber-reinforced plastic (FRP) beams is described in this paper. Results of tests on commercially produced pultruded E-glass/polyester and E-glass/vinylester composite material wide-flange I-beams are described. The beams were tested in a four-point bending configuration in a specially designed fixture which was designed to cause local buckling and ultimate failure of the compression flange of the beams and to avoid global lateraltorsional buckling and local web failure. All beams were monitored with strain gages and LVDTs. Buckling loads, failure loads, buckling stresses, deflections and failure modes are reported. Standard and "customized" pultruded beams in the 8 inch (203 mm) series were tested. Based on an analysis of the performance of the standard 8 x 8 x 3/8 in. (203 x 203 x 9.5 mm) beams, two 8 x 8 x 3/8 in. (203 x 203 x 9.5 mm) beams were "customized." In these "customized" beams the fillet region at the flange and web intersection was altered in order to increase its strength and the rotational stiffness. Analysis of the test results of the customized beams indicated that significant increases in load carrying capacity of pultruded beams can be achieved with minor geometry and fiber architecture modifications to the standard beams. A discussion of the differences in buckling and failure characteristics of the beams based on their resins, sizes, and custom modifications is provided.