STRENGTH OF CONCRETE SLABS IN PUNCHING SHEAR.

A theoretical solution for the punching shear strength of a concrete slab is presented. The problem is treated as a three-dimensional axisymmetrical one, the material being assumed to be rigid-plastic. A failure criterion for the concrete is suggested, in which a second-degree parabola is used for a Coulomb-Mohr yield envelope. By establishing the virtual work equation, an upper-bound solution is obtained, which is simpler than the well-known M. W. Braestrup-M. P. Nielsen solution. It can also give the ultimate punching shearing load when the punch angle is smaller than the angle of friction of concrete. Simplified expressions for the ultimate strength of a concrete slab in punching shear with different degrees of simplification are also suggested for practical use. The normal, shearing, and principal stresses along the failure surface are also explored.