Failure of concrete concentrates in the particular zone: the localized compressive failulre zone, when uniaxial compressive force applies. It has been investigated how localized compressive failure is influenced by material properties, shapes and dimensions of concrete. However, mechanism of localized compressive failure has not been made clear completely to date. In this study, for comprehending phenomenon of localized compressive failure of concrete, uniaxial compressive loading tests were conducted on concrete specimens with different shapes and dimensions of cross-section, height of specimen, and compressive strength. Local strains in concrete were measured during loading to determine the length of localized failure zone. Acoustic emission signalsdue to microcracks in concrete were also measured to establish a simple method to estimate the length of localized failure zone. Furthermore, visualization of cracks in concrete was tried to perform by X-ray CT scanning on failed specimens.
　Based on these results, a new stress-strain relationship of concrete was formulated in consideration with the localized compressive failure. In the formulation, concrete was separated into failure zone and unloading zone, and the energy absorbed in each zone was appropriately taken into account. consequently, a new constitutive law of concrete subjected to uniaxial compression was proposed, which enabled to accurately evaluate mechanical behavior of concrete even after the peak load.