Shear strength model and prediction of failure mode for multi-spiral column

The damage of reinforced concrete columns due to shear is often serious, so this type of failure should be avoided from the design. In this paper, a model derived based on the discrete computational method is proposed to calculate the shear strength of column carried by multi-spiral transverse reinforcement, accounting for the effect of compression depth. Furthermore, based on this model, a method is proposed to predict the failure mode of multi-spiral columns. The test database of multi-spiral columns from previous studies is used to validate both the shear strength and failure mode predictions. The proposed model with a crack angle of 40 degrees gives the best estimation of the shear strength of multi-spiral columns, and the proposed method predicts well the failure mode of these columns. To avoid shear failure, the ratio of the minimum shear strength calculated from the proposed model with a crack angle of 40 degrees to the shear force based on the moment-curvature analysis is suggested to be larger than 1.2.