Fracture behavior of RC members subjected to bending shear and torsion using acoustic emission method

Japan is one of the most earthquake-prone countries in the world and therefore urgent seismic countermeasures are needed. The Great Hanshin Earthquake occurred in Hyogo Prefecture in January 1995, and several reinforced concrete (RC) piers on the Hanshin Expressway collapsed. course of the collapsed RC piers, the effect of torsion was estimated at the main cause about 11% among the damaged RC piers. Since construction of asymmetrical RC structures has increasing in urban areas, those asymmetrical piers could receive torsion forces. From previous research, it is known that RC members loaded by pure torsion generated spiral cracks on the entire surface. In addition, when RC members are loaded by bending shear and torsion, major cracks are found on one side while minor cracks are found on the opposite side. As a result, RC members would rapidly be broken; in the present paper, in order to clarify the fracture behaviors and fracture energy in RC members under torsion, acoustic emission (AE) measurement applied. Concerning fractures in RC members loaded by pure torsion, the fractures progress only in the outer circumference of the cross section until the web reinforcement yields. Here, the pure torsion fracture and the bending shear destruction are the primary factors in controlling the shear flow of RC members loaded by bending shear and torsion, before they reached one-third of the maximum strength.