Numerical simulations of the load-slip behaviour of rebar shear connectors in composite members

Abstract

Shear connectors are generally provided to achieve composite action between the concrete slab and the supporting steel beam by transferring horizontal shear force across the interface. This paper investigates the strength and failure behaviour of rebar shear connectors embedded in solid concrete slab. A nonlinear 3D finite element (FE) model was developed using ABAQUS to simulate the push out test of rebar shear connector in solid concrete slab. The Concrete Damaged Plasticity model was used to simulate concrete failure behaviour. In this study, general static implicit solution strategy with stepwise displacement loading was applied to trace the experimental load versus slip behaviour of rebar shear connectors up to failure. The finite element model developed in current study was successful in predicting the ultimate shear capacity available in literature. The mean value of the ratio of numerically obtained load capacity and experimentally obtained load capacity (PFEM/PEXP) was found to be 1.0 (ranged from 0.76 to 1.2) with a standard deviation of 0.12. The finite element model was also capable of predicting the failure behaviour of the push-out specimens as observed during the test. A parametric study was also conducted using the validated FE model. The parametric analysis showed the effect of rebar strength and concrete strength on the shear capacity of 16 mm, 20 mm, 25 mm and 32 mm rebar connectors. In the parametric study concrete strength was varied from 30 MPa to 50 MPa with an intermediate value of 40 MPa and connector strength was varied among 275 MPa, 415 MPa and 500 MPa. Higher strength bars are more likely to show better ductile behaviour than lower strength bars. Increasing the concrete strength from 30 MPa to 50 MPa, around 40% increase in shear strength was obtained for 25 mm diameter connectors with 500 MPa yield strength. Higher diameter rebars with high yield strength, higher increase in shear capacity is observed than lower diameter connectors having lower steel grade with the increase in concrete strength. The AISC 360-16 design formula for stud connector overestimates the shear capacity for rebar shear connectors. Analyzing 33 parametric push-out test simulations, a modified design equation (based on AISC 360-16 equation for stud connectors) is recommended for determining the ultimate shear capacity of rebar shear connectors embedded in solid concrete slabs.