Pull-out strength of thin perfobond connectors and C-ties in steel-concrete-steel sandwich composite structures

Abstract

Due to the remarkable mechanical property, short construction period, and labor-saving features, steel-concrete-steel (SCS) sandwich composite structures are widely used in assembled buildings, modularized immersed tunnels, and bridge cable pylons. In SCS sandwich structures, sufficient pull-out resistance in connectors is necessary to effectively prevent outward buckling of the outer steel faceplates. However, the existing connectors remain deficient in terms of load bearing capacity, ductility, and construction convenience. A novel type of connector named thin perfobond connector and C-tie (PBL-CT) was proposed to address these problems in this paper. While retaining the superior shear performance of traditional perfobond connectors (PBLs), the addition of C-ties in PBL-CTs enhances structural shear resistance. Through 18 monotonic pull-out tests, the pull-out performance of shallow-embedded thin PBL-CTs was investigated. Test results revealed that the primary failure mode of shallow-embedded thin PBLs was cracking of the surrounding concrete, with C-ties significantly improving the pull-out performance and shifting the failure mode to a combination of concrete breakout and perforated rib rupture. A nonlinear finite element (FE) model was developed and calibrated to conduct parameter analyses on concrete strength, embedment depth, and perforated rib parameters. This led to the establishment of a mixed failure model for shallow-embedded thin PBL-CTs. The ultimate pull-out bearing capacity was found to comprise two components: the pull-out resistance of the concrete cone and the shear resistance of the perforated rib. A regression-based prediction formula was derived, providing accurate and conservative predictions of the ultimate pull-out bearing capacity of shallow-embedded thin PBL-CTs.