Abstract
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.
Highlights
A number of different design codes are used for punching shear [1,2,3]
The approach adopted in the Eurocode for the punching shear resistance of slabs without shear reinforcement is empirical and assumes that the shear resistance is derived from a shear capacity acting uniformly over the effective area of the section considered
The punching shear resistance of the slab without shear reinforcement (S1) yielded a conservative load estimate of 201 kN in comparison with the experimental failure load of 256 kN which questions the reliability of the method for small cross-sectional slab depths
Summary
A number of different design codes are used for punching shear [1,2,3]. In Ireland, the design of concrete structures follows the guidelines in [3] which are based on Model Code 1990 [4]. The Eurocode 2 [1] approach for designing against punching shear failure in solid concrete slabs defines the critical control perimeter (u1) as shown in Figure 1 where d is the mean effective depth of the slab. This perimeter should be minimized, examples of which are shown in Figure 2 for different cross sections. The approach adopted in the Eurocode for the punching shear resistance of slabs without shear reinforcement is empirical and assumes that the shear resistance is derived from a shear capacity acting uniformly over the effective area of the section considered
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
