Joint Strength of Single-Bolted Pultruded GFRP Square Hollow Sections with Mechanical Inserts under Elevated Temperatures

Abstract

The sensitivity of the joint performance of pultruded fiber reinforced polymer (FRP) to elevated temperatures has been known to limit the widespread application of FRP composites in civil construction. This paper presents a study of the effect of elevated temperatures and mechanical inserts on the joint strength and failure mechanism of a square hollow section (SHS) of pultruded glass FRP (GFRP) composites. Three pultruded GFRP bolted joint configurations were implemented— namely, a joint without mechanical insert (N), a joint with mechanical insert with tight-fit attachment (I), and a joint with mechanical insert bonded with epoxy adhesive (G). Sixty (60) square pultruded GFRPs with a single all-threaded bolt connection each were tested up to failure at room temperature 40°C, 60°C, and 80°C. Specimen G exhibited the highest joint strength, with twice more than that of Specimen N across the temperature range. Specimens N and I failed by shear-out at high temperatures mainly due to the deterioration of the interfacial bond between the fibers and the matrix. The strength reduction factor, k, and modification factor, m, which incorporate the increasing temperatures and the designed joint configurations showed excellent agreement when compared to the experimental results.