Simplified Buckling-Strength Determination of Pultruded FRP Structural Beams

For many decades, both the lateral-torsional and local buckling strengths of fiber-reinforced polymer (FRP) structural members have been studied extensively by numerous researchers and designers. Many complex prediction models and equations of the buckling strength have been proposed. Typically, most design communities prefer simpler design procedures and equations. Simplified, albeit approximate, buckling-strength equations of pultruded FRP structural beams have been proposed with acceptable accuracy. Herein, the proposed buckling-strength results were compared with those based on prestandard equations and available experimental data. The proposed simplified prestandard lateral-torsional buckling equation provided higher strength results than the experimental data based on the upper-bound experimental results by approximately 11%. Also, the proposed simplified lateral-torsional buckling-strength equation was reasonably acceptable for the design purpose (within 18% difference) compared to the predicted strength provided by the prestandard equations. For local buckling strength, the maximum percentage difference in local flange buckling strength was found to be less than 15%, whereas the proposed web local buckling-strength equations provided excellent agreement with the predicted strength (i.e., less than 5% difference for all cross sections). The proposed design equations are very useful in enabling improved design calculations of FRP structural members.