Effects of Posttensioning Slippage on 2-Way Spanning Concrete Slabs

This paper investigates the effect of improper posttensioning of a 2-way spanning concrete slab subject to a central point load. Due to plate slippage alone, the support conditions only offered a 1-way spanning action which could have led to premature failure with dangerous consequences. Posttensioning can strengthen a flat slab against punching shear by controlling deflections and cracking under service loads compared with traditional punching shear reinforcing methods leading to more slender structures and economic solutions for longer spans. However, if the method is not properly applied, these thinner floor plates can fail in a brittle and sudden manner by punching at ultimate limit state and excessive deflection in serviceability. Concrete slabs containing traditional shear reinforcement performed adequately and demonstrated that the critical punching shear perimeter, defined as twice the depth of the slab, was confirmed from measured deflections and crack pattern analysis.

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