Seismic Cracking and Strengthening of Concrete Gravity Dams

Abstract

Concrete gravity dams designed in compliance with the present specification are likely to experience cracking under intense shaking like maximum credible earthquakes. Dangerous cracking in dam body should be prevented in advance to ensure the serviceability of dams. In this paper, the safety of concrete gravity dams under strong ground motions is investigated. First, the dam response during earthquakes is simulated by the FE-BE method, including the damfoundation-reservoir interaction. The nonlinear tensile behavior of concrete is represented by the smeared crack model to predict the possible earthquake-induced cracking in the dam body. Then some measures to prevent the cracking of dam body are presented. The measures are, for example, adjustment of dam section, local reinforcement and post-tension technique. The adjustment of dam section will reduce the tensile stress in dam body and avoid the occurrence of cracking. Local reinforcement at possible cracking positions is expected to resist the propagation of cracks and reduce the damage of dam body, although it might not prevent the initial cracking. Post-tension technique exerts pre-compressive stress in dams to offset the tensile stress during earthquakes. Effects of these measures are evaluated by numerical simulation. It is shown that these measures could improve the cracking-resistant behavior of concrete gravity dams effectively.