Push-out behavior and shear capacity prediction of PBL connectors in hybrid double-skin tubular members (DSTMs)

Shear connectors are key components in hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs). To study the push-out behavior of perfobond (PBL) connectors in hybrid DSTMs, push-out tests were conducted on eight samples with different arrangements of PBL shear connectors. The samples were designed to have double holes (in discontinuous and twin arrangements) and triple holes in one PBL plate. The tests identified the major contributions from concrete end bearing and the PBL bar. The samples with discontinuous and twin PBL arrangements (which have additional concrete end bearing contributions) exhibited greater cracking loads and more pronounced plastic ascending slopes than the continuous PBL arrangement, while only small differences in their shear capacities (less than 10 %) were observed, suggesting that the PBL bars play a major role in shear resistance. Moreover, a test database with 20 datasets was compiled for PBL shear connectors in DSTMs, against which current design codes and selected models performed poorly in predicting shear capacities (with absolute average errors (AAEs) ranging from 30 % to 40 %). In response, a new model, which was verified to have a high level of accuracy (AAE of 7.8 %), is proposed for estimating the shear capacities of PBL shear connectors in DSTMs.