Experimental Evaluation on Effect of Openings on Behavior of Prestressed Precast Hollow-Core Slabs

Prestressed precast hollow-core slabs are generally machine-cast with prestressing strands as only flexural reinforcement with no shear reinforcement. Various mechanical, electrical, and plumbing service requirements require openings to be provided in these precast slabs. Openings in hollow-core slabs can coincide with the location of strands and may lead to their curtailment. The size of these openings can vary from minimal, causing no change, to very large, causing adverse effects on the structural behavior of the slab. An experimental study was carried out to evaluate the effect of openings in hollow-core slabs. Six full-scale tests were conducted by considering shear span-depth ratio and location of openings as parameters. The strength of concrete, prestressing ratio, and size of opening was kept constant in all slabs. It was observed that the provision of openings not only reduced the cracking and ultimate strength of slabs but also altered the failure modes with change in deformation capacity. Experimental results were compared with predictions of code equations and finite element analysis (FEA) based software. A fair correlation was observed between the test results and finite element (FE) predictions. The FE modeling approach of hollow-core slabs suggested in this study can be used further for parametric studies and to develop design equations.