Behaviour of GFRP Stiffened Cold-Formed Steel Built-up Beams

This article explores a novel approach to inhibit local premature failures in cold-formed steel (CFS) beams and enhance their flexural capacity by introducing external web stiffeners to buckling prone regions. An experimental and finite element investigation on the behaviour of doubly symmetric CFS built-up channel beams with adhesively bonded glass-fiber reinforced polymer (GFRP) stiffeners is presented in this paper. Unlike previous attempts, where flat plates have been used, the results of pultruded T-shaped GFRP stiffeners on the flexural capacity and local failure inhibition of the CFS beams are presented. The viability of suggested strengthening arrangement is assessed by comparing the results from CFS beams strengthened with steel stiffeners of equivalent stiffness. One control and six reinforced beams, stiffened with different configurations of both steel and GFRP stiffeners in the moment span, were tested up to failure under four-point bending. The change in the mode of failure from buckling at discrete regions to global failures with an improvement in the flexural capacity by up to 39% was achieved using adhesively bonded external stiffeners in the present study. It can be concluded that adhesively bonded GFRP stiffeners provide a cost-effective and adequate alternative to enhance the flexural performance and inhibit the local failures in thin-walled beams. Finite element models were developed and verified against test results. FE models were found to be capable of predicting the ultimate capacity and failure of stiffened beams with fair accuracy.