Stiffness and strength of web–flange junctions of pultruded GRP sections

Abstract

A simple method of testing pultruded glass reinforced plastic (GRP) wide flange (WF) profiles to determine the rotational stiffness and strength of their web–flange junctions is described. Equal and opposite tensile forces are applied near to the edges of the upper and lower flanges on one side of the section and the separation of the flanges is monitored. Equations are presented for the calculation of the rotations in the web and flange at the web–flange junction. They require only force and displacement data derived from tests on short lengths of WF section. The calculated rotations are used to determine the rotational stiffness of the web–flange junction. Details of two groups of six test specimens for two sizes of WF section are presented. The test set-up and test procedure are outlined. Typical load–displacement responses for each WF section specimen size as well as typical web–flange junction failure modes are presented. How the test results have been used to calculate the rotational stiffnesses of the junctions is explained. Failure loads, failure moments and initial rotational stiffnesses of the web–flange junctions of both sizes of WF section are presented together with values for the transverse elastic moduli of their webs. The average rotational stiffness of the web–flange junction of the smaller WF section was about 70% of that of the larger WF section. The average transverse elastic modulus of the web of the smaller WF section was about 5% lower than that of the larger WF section and both values were between 53% and 61% greater than the manufacturer's stated minimum value.