Punching shear of reinforced concrete flat plates : behavior and design considerations




Polo Gonzalez, Gabriel Eduardo

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The use of flat plates (i.e., slabs without capitals, drop panels, or supporting beams) in reinforced concrete (RC) building construction has become widespread throughout much of the world. In comparison to other slab types, RC flat plates are often more efficient from a construction standpoint due to their simplified geometries and reduced formwork requirements. However, the complexities of the load transfer mechanisms developed in these systems are still not fully understood. The research presented in this dissertation was aimed toward expanding the current knowledge regarding the punching shear behavior of RC flat plates by investigating the response of slab-column connections under highly-controlled two-way shear loading conditions. The influence of through-thickness shear reinforcement, longitudinal reinforcement ratio, and connection region loading conditions have been investigated and presented in three technical papers which summarize the key findings obtained from the testing of twelve full-scale connection specimens and the supplemental analytical efforts. In the first paper, the performance of RC flat plates employing an alternative shear reinforcement system consisting of inclined deformed reinforcing bars is compared to slabs constructed with conventional reinforcement. The findings showed that premature failures attributed to inadequate reinforcement anchorage controlled the performance of the slabs and limited the benefit provided by the inclined stirrups. In the second paper, the punching shear performance of headed stud reinforced slabs that were constructed with either a cruciform or a radial stud layout, was investigated. Results showed that both shear stud layouts improved the shear-resisting behaviors of the slabs and produced structural responses that were comparable in nearly all aspects. In the third paper, slabs subjected to different sectional loading conditions were examined to assess the influence of loading composition on flat plate shear resisting performance. Experimental work was complimented with numerical analyses and the results indicated that the punching shear response of flat plates is greatly influenced by flexural demands. Further, it was found that the loads experienced by slab specimens tested using common procedures may not be representative of loading conditions experienced by flat plates in service.


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