Experimental and numerical study of the bond-slip relationship for post-tensioned composite slabs

Post-tensioned composite steel-concrete slabs provide an attractive combination of the structural advantages of post-tensioned concrete slabs and profiled composite slabs in building floor systems. The bond between the concrete and the profiled steel sheets is usually assumed to have a significant effect on the strength, stiffness and ductility of these types of slabs. Push tests provide a less expensive and convenient method to investigate the complex interaction between the profiled steel sheets and concrete, in spite of some obvious differences of behaviour between small scale tests and composite slab bending tests. In this context, this paper presents results from a push test study incorporating post-tensioning at the steel bar to apply precompression to the concrete in order to determine the potential influence of prestress on the bond between the profiled steel sheets and concrete. The parameters investigated in this study were (a) level of prestress and (b) bond length. The results of this study indicated that the prestress has a detrimental effect on the bond between the profiled steel sheets and concrete in post-tensioned composite slabs. This is an important finding which needs to be considered in the ultimate strength determination of post-tensioned profiled composite slabs. This paper also presents a three dimensional nonlinear finite element model of post-tensioned push specimens. The results indicated that incorporating the effects of prestress produces satisfactory results for the overall bond stress-slip behaviour of post-tensioned push test specimens.