The study of the punching shear resistance of thick plates and shells made of reinforced concrete will be conducted. In order to perform the study, a new constitutive law for cracked concrete will be developed which allows cracks to form in many non-orthogonal directions and which correctly models the interface shear transfer characteristics of concrete, in particular the friction and dilatancy behavior of cracks in combination with the fracture energy associated with the crack. Existing test results will be analyzed and used to quantify and refine the improved material models. The analytical study will be performed using two dimensional finite elements, solid three dimensional finite elements and a new innovative approach to layered plate and shell elements whereby shear deformation is more accurately represented than in usual layered theory. Further, both the possibility of shear failure and the inclusion of stirrups are considered. A series of plates and shells will be analyzed to verify the validity of the approach and the appropriateness of the new material models. The final series of plates and shells to be analyzed will be the series of tests that were recently performed at the National Bureau of Standards under a separate contract. These tests simulate punching shear due to concentrated ice forces acting on offshore structures. These tests have already been analyzed reasonably successfully using improved material models. Finally, the program developed will be used to perform a series of parameter studies in order to develop simplified design equations. Parameters to be studied include shear reinforcement ratios, shell curvature, and boundary conditions.
