| Experimental and numerical studies were carried out to investigate the punching shear strength of post-tensioned concrete flat slab-interior column connections under the effects of gravity loads and lateral displacements induced by earthquakes. Seven full-size post-tensioned slab-interior column connections were tested under gravity loads combined with cyclic displacement reversals of increasing amplitude up to failure. The ratio of prestressed to non-prestressed reinforcement was varied, while the flexural strength was constant. The slabs were reinforced with headed studs, a type of shear reinforcement that had been developed at the University of Calgary. The objective of this experimental program was to verify the applicability of the seismic provisions of the North American codes as well as other seismic design procedures, proposed earlier, when used for prestressed slabs.; The tested connections showed that varying the prestressing compressive stress, fpc, from 0.4 to 1.1 MPa (60 to 150 psi) has no significant effect on the unbalanced moment strength or the ductility; finite-element analyses permitted the extension of the range of f pc to 1.4 MPa (200 psi). Effectiveness of stud shear reinforcement, when used in prestressed flat slab structures, was confirmed. Furthermore, it was shown that prestressing mitigates degradation of the connection's stiffness; however, energy dissipation is better in non-prestressed connections.; A commercial non-linear finite-element analysis software was used to investigate the punching strength of prestressed slab-interior column connections, subjected to simulated earthquake loading. The analyses served to study the effect of varying design parameters that could not be covered in the physical experiments. The finite-element model was described and verified using the results of the experimental program conducted in this research. Analysis results, combined with the test results, showed that existing seismic design procedure, for non-prestressed slabs, is also applicable for prestressed slabs having fpc = 0.4 to 1.4 MPa (60 to 200 psi). |
