Abstract
Upper slabs of caisson foundation are RC planar members with small shear span ratio to which all surroundings under the outside edge are supported. However, neither consideration method as the planar member nor the influence of eccentricity of the load is clarified in the shear design of upper slabs. Moreover, the shear strength of slabs with very small shear span ratio is not clarified though there is a tendency that the shear span ratio of upper slabs is reduced by the revision of seismic design. Then, the method of calculating the shear strength based on the load testing result of the model of upper slabs of caisson foundation was examined. As a result, it was concluded that the shear strength of upper slabs can be calculated by considering the peripheral length of shearing fracture area.
