Punching Shear Behavior of Externally Prestressed Concrete Slabs

Abstract

The use of externally post-tensioned fiber-reinforced concrete decks in highway bridge structures is seen as a viable option in the move toward the design and construction of high-performance structures. However, with the thin unreinforced deck slabs that may result, punching shear is a potential concern. An experimental program is described in which the punching shear behavior of externally prestressed slabs is investigated, both with plain and fiber-reinforced concrete specimens. Results indicate that significant improvements in strength, ductility, energy absorption and nonbrittleness of failure can be achieved with fiber reinforcement. Nonlinear finite-element analysis procedures are used to model the specimens, and reasonably accurate simulations of behavior are obtained. Design code procedures are found to be unconservative in estimating the punching shear strength of these elements, whereas a commonly used analytical model is found to be overly conservative.