Load-carrying capacity of reinforced concrete (RC) members with lightweight concrete is lower in comparison with that of RC members with normal-weight concrete with the same compressive strength. This phenomenon depends on the fracture behavior of which the lightweight concrete is comparatively brittle to the normal-weight concrete. For the load-carrying capacity of RC members with the lightweight concrete, several reduction factors, which are applied to that of RC members with the normal-weight concrete, have been investigated by some researchers so far. The authors have been studied on the punching shear capacity of reinforced lightweight concrete slabs with the expansive shale aggregate. In the past studies conducted by the authors, the proposed reduction factors were constant values without a multiplicity of uses. In this paper, therefore, the applicable reduction factor to some kinds of lightweight concrete is derived in consideration with the fracture characteristics of the lightweight concrete. Consequently, the proposed method on punching shear capacity of the reinforced lightweight concrete slabs gives appropriate predicting values.
