Minimum flexural reinforcement for punching resistance of concrete slabs
Date
2012
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Abstract
This thesis presents a new design criterion for punching shear strength of flat-plates. Slabs at their connections with columns can fail due to punching shear or flexure. When the primary failure is by flexure, it can trigger a secondary failure by punching. Experimental verification of this phenomenon is presented. The punching shear design equations in the Canadian Standard, CSA A23.3-2004 and the American Concrete Institute Building Code, ACI 318-2011 conservatively predict the punching strength of slabs only when the provided amount of flexural reinforcement is sufficient to resist the corresponding bending moment. The new criterion can predict the punching shear strength for slabs having any amount of flexural reinforcement. The criterion is based on the punching shear design equations in CSA A23.3-2004 or ACI 318- 2011 codes supplemented by the yield-line theory. The new criterion is: For a reinforced concrete slab, with or without shear reinforcement, subjected to the transfer of a concentric or eccentric shear force at a column connection, the governing nominal strength is the smaller of the shear force capacity predicted by the yieldline theory and the shear force capacity based on the punching shear equations in the applicable code. The safety with the new criterion is verified using the results of published tests and the results of three dimensional nonlinear finite element analyses. A higher level of safety can be achieved when the design for punching shear is based on the new criterion combined with the current CSA A23.3-2004 or ACI 318-2011 codes. The new criterion predicts a lower punching strength compared to the codes only when the flexural reinforcement ratio at the slab-column connection is relatively low. The new criterion specifies the minimum amount of flexural reinforcement in a flat plate, at column connections, to resist the specified eccentric or concentric shear force. Provision of the minimum amount of flexural reinforcement ensures that the slab does not fail prematurely by flexure due to the development of a local yield-line mechanism.
Description
Bibliography: p. 252-269
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Citation
Peiris, H. C. (2012). Minimum flexural reinforcement for punching resistance of concrete slabs (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/4728