Load and resistance factor design (LRFD) approach for bolted joints in pultruded composites

Abstract

The application of glass fiber-reinforced polymeric matrix composites in civil engineering structures has been increasing rapidly in recent years. Pultruded composites are attractive for structural applications because of their continuous production and excellent mechanical properties. The present study is intended to be a step in understanding bolted joints in pultruded composites. Specifically, bolted connections in pultruded plates are investigated for their block shear and net tension failure modes. Configurations and dimensions have been selected to highlight the block shear and net tension failure phenomena and to compare the behavior of composites to the standard practice in the case of steel connections. Specimens with single and multiple holes have been tested in tension under bolt-loading conditions. Some of the specimens were instrumented with strain gages and the load-strain responses were monitored. The failed specimens were examined for the cracks and fracture patterns. The results have been analyzed using the strength calculations similar to those used in the load and resistance factor design (LRFD) procedures for steel structures. Two LRFD-type formulae for block shear and net tension failure for pultruded composites are proposed in the present paper. It was found that the failures in the bolt-loaded pultruded specimens could be predicted reasonably well with the proposed formulae. The use of these formulae is also demonstrated by means of examples. The proposed resistance factors are checked with additional test results.