Flexural behavior of assembled FRP-steel Pre-Tightened Teeth Connection (PTTC): Experimental study and failure mechanism

The study focused on examining the flexural failure behavior of a newly developed assembled FRP-Steel pre-tightened teeth connection (PTTC) used for rapidly assembly of pultruded fiber reinforced polymer (FRP) tubular beams. Four-point bending loading tests were conducted on a specific type of assembled joint that incorporates the FRP-Steel PTTC and threaded connections. The results indicated that each component demonstrates typical flexural behavior with desired load-bearing capacity. The assembled FRP-steel PTTC exhibits a gradual occurrence of various failure modes, which differed significantly from those observed under uniaxial compressive or tensile loadings that typically exhibit a more singular failure mode. The initial failure is identified as the local transverse shear failure occurring at the upper junction interface of the composites between the FRP segments and the external steel sleeves. It is thus crucial to carefully assess the stress concentration effects during the design process of the bending FRP-steel PTTC and its assembled joints. Corresponding numerical analysis was performed and compared against experimental results whilst demonstrating good agreement in relation to deformation, initial failure modes, and bearing capacity. The elicited comparisons indicated that the developed numerical model is capable of predicting the flexural behavior prior to the initiation of the failure process of the assembled composite joints.