Experimental investigation on the flexural-torsional buckling behavior of pultruded GFRP angle columns

In this paper, the findings from an experimental investigation on the flexural-torsional buckling behavior of pultruded glass-fiber reinforced polymer (GFRP) angle columns are reported and discussed. The program included the study of two sizes of equal-leg angles made with different resins (polyester and vinylester). Prior to testing, a detailed material characterization was carried out and signature curves (critical load x length) were obtained using a generalized beam theory (GBT) software for predicting critical loads. Lengths were selected in order to ensure 'pure' flexural-torsional buckling, in a range of slenderness not studied in previous works. Twenty-two members with fixed ends and clamped walls were tested in concentric compression and had their motions measured during loading. Load-deflection curves are presented and the influences of post-buckling reserve of strength, damage and differential rotation of legs are discussed. Experimental critical loads obtained using Koiter's method are reported and shown to be in good agreement with GBT predictions. Finally, a design recommendation through the use of a Winter-type equation accounting for the plate-like behavior is made.