Analytical shear-slip models of J-hook connectors in steel-concrete-steel sandwich composite structures

Steel-concrete-steel sandwich composite structures (SCSSCSs) with J-hook connectors exhibit superior structural performances under static and dynamic loads. This study developed an analytical shear-slip constitutive model for J-hooks in SCSSCSs. Firstly, a database comprising 119 push-out tests of J-hooks with a loading rate of 0.05 mm/min was established to illustrate their general shear-slip failure modes. The database includes various concrete types with compressive strength ranging from 18.1 to 71 MPa and J-hook yield strength from 280 to 515 MPa. Subsequently, a finite element model (FEM) was developed to reveal the load-transfer mechanism of J-hook connectors. Based on the mechanical insights, a four-stage analytical model was developed with characteristic indexes of elastic stiffness, yielding strength and slip, peak shear resistance and slip, and ultimate slip. Extensive validations against the reported test results confirmed the accuracy of developed shear-slip analytical models. Finally, step-by-step procedure was proposed to establish full-range shear-slip curves of J-hooks. The proposed shear-slip constitutive model can be directly used in numerical simulations with simplified beam or spring elements, improving analysis efficiency without using complex solid elements.