Abstract
In this paper, we examined the ultimate shear strength of four-pile caps based on 82 specimens that tested by authors. Firstly, we classified the shear failure types into three types based on the last failure situation. Next, we proposed equations to estimate the ultimate shear strength of each failure type. In regard to the ultimate shear strength the results of the test were compared with calculated values according to the equations proposed by others as well as to that by authors. To conclude the discussions the calculated values according to the authors' equations agreed well with experimental results.