In designing superstructures of buildings, it is important to estimate the ultimate bearing capacity of their foundations. The ultimate bearing capacity formula for foundations, which is specified in the guidelines published by the Architectural Institute of Japan for design of building foundation, is widely used by engineers. Recently, the evaluation of bearing capacity of foundations under large earthquakes has keenly been focused on. As the foundation width increases, its ultimate bearing capacity gets smaller than the capacity obtained by Terzaghi's formula for sandy grounds that is caused by the decline of their inertial friction angle or the progressive failure. Besides, the ultimate bearing capacity of large foundations against inclined loads has not been yet made clear. In this paper, by using rigid plastic finite element method, the ultimate bearing capacity of large foundations against inclined load is discussed. The obtained results of the FEM analysis are as follows. 1) The “size effect” can be explained analytically in the large spread foundation. by referring to some experimental, in which the friction angle declines when the mean effective stress becomes high. 2) for the friction angles 30 and 40 degrees, the size effect should be considered. However, in the case of the inertial friction angle of 40 degrees, the size effect is slightly smaller when compared to the case of 30 degrees.
