Experimental investigation on failure behavior of a novel high-tensile FRP-metal crimped thread connection
Abstract
(FMCTC) is developed for lightweight emergency truss bridge system constructed with pultruded FRP tubes. Experimental investigations were conducted to evaluate the feasibility, manufacturability, tensile behavior, and failure mechanisms of this new composite connection. The results reveal that the design successfully eliminates secondary processing and specialized tooling of parent FRP tubes; instead, composite threads are efficiently formed via passive crimping equipment. By integrating spiral-crimped thread geometry with preloaded high radial pressure, the specimens achieve 65% connection efficiency relative to base FRP strength. Two dominant failure modes are identified: (i) primary shear failure of the crimped FRP threads followed by interfacial slippage, and (ii) secondary failure patterns involving localized cross-sectional fractures coupled with longitudinal cracking in extended FRP tubes. Notably, despite distinct failure modes, all specimens exhibit minimal variation in ultimate loads. The substantial bearing strength, reaching up to 836.3 MPa, is governed by the shear resistance mechanism of the FRP threads. Owing to its manufacturing simplicity, enhanced connection efficiency, and exceptional load-bearing capacity, the newly developed FMCTC offers a viable technical solution for practical deployment in lightweight emergency truss bridge systems.