Abstract: Based on test results, a new collapse mechanism of punching shear failure of concrete slabs is established in this paper. The twin shear strength theory is used in the plastic limit analysis to obtain the punching shear capacity from the failure cone. It is suggested that the ultimate punching shear strength of reinforced concrete slabs consist of the punching resistance capacity of the failure cone and a part of flexure strength of the whole slab. The formulas are provided to calculate the strengths of ordinary-strength concrete slabs, high-strength concrete slabs, steel-fiber reinforced ordinary-strength concrete slabs and steel-fiber reinforced high-strength concrete slabs subjected to punching shear. Good agreement between the present theoretical values and available experimental results is achieved.