Discussion of 'Local Buckling of Fiber Reinforced Plastic Composite Structural Members with Open and Closed Cross Sections' by Laszlo P. Kollar

摘要

Explicit expressions are presented by Kollar to determine the critical local buckling load of fiber-reinforced plastic (FRP) composite beam and column members with open and closed thin-walled sections. In the derivation of the presented expressions several approximations were made, such as that the plate material has to be orthotropic and symmetrical with respect to the mid-plane. The material is assumed to behave in a linearly elastic manner and the deformations are small. The performance of the new expressions to determine buckling loads is demonstrated by numerical examples. For concentric columns of pultraded FRP composite, Mottram (2004a) has compared the local flange buckling loads predicted using nine closed-form expressions against instability loads from physical testing. The FRP section shape is wide flange (Anon 2001), having the same flange and web widths (b_w = b_f) and the same plate thicknesses (f_w = f_f). The pultruded material can be assumed to be orthotropic and the fiber reinforcement arrangement is symmetrical. Since the Kollar expressions, for this buckling case, were unavailable when the comparison was made, it is instructive to see how they compare against the other expressions presented in Mottram (2004a). The advancement made by the Kollar's expressions is that they, for the first time, include the important influence on the critical load of the web/flange torsional restraint. Previously this had been achieved only by way of numerical analysis that was needed to calculate, at least, one numerical parameter in the closed-form expression for the critical local buckling load (Mottram 2004a).