Modelling failures in existing reinforced concrete columns

Experimental research and post-earthquake reconnaissance have demonstrated that reinforced concrete columns with light or widely spaced transverse reinforcement are vulnerable to shear failure, and in turn, axial failure during earthquakes. Based on experimental data, failure surfaces have been used to define the onset of shear and axial failure for such columns. After the response of the column intersects the failure surface, the shear or axial strength of the column begins to degrade. This paper introduces a uniaxial material model that incorporates the failure surfaces and the subsequent strength degradation. When used in series with a beam-column element, the uniaxial material model can adequately capture the response of reinforced concrete columns during shear and axial load failure. The performance of the analytical model is compared with results from shake table tests.Key words: shear failure, axial failure, beam-column elements, failure surface, earthquakes, reinforced concrete, columns, collapse, structural analysis.