Infoscience

Journal article

Punching shear tests on compact footings with uniform soil pressure

Punching shear is usually the governing failure criterion for the select ion of the depth of reinforced concrete footings. Despite the fact that large experimental programmes have been performed in the past aimed at the punching strength of slender flat slabs, only a few experimental campaigns on full-scale compact reinforced concrete footings can be found in the literature. In this paper, the results of an experimental programme including 8 reinforced concrete footings with a nominal thickness of 550 mm is presented. These experiments investigated the influence of the column size, member slenderness and the presence of compression and shear reinforcement. The test s were performed using an innovative test setup to ensure a uniform soil pressure. The experimental results show that the slenderness influences the punching shear strength as well as the effectiveness of the shear reinforcement. It is also experimentally shown that an important interaction amongst bending and shear occurs for high levels of shear forces near the column (typical case of compact footings or members with large amounts of shear reinforcement). Different continuous measurements recorded during the experimental tests allow a complete description of the kinematics and strains at failure. On that basis, experimental evidence is obtained showing that crushing of the concrete struts near the column is the phenomenon that triggers the punching failure of compact footings.

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