Study of dynamic fracture of structure and anti-earthquake design under near-source earthquake

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Initial transient behavior of a tall-building-model due to a strong near-source earthquake has been numerically studied using the code MSC/DYTRAN.It is found that stresses greater than the yield stress of the column material, for an elastic/plastic building-model, and stresses greater than the tensile strength of the column material, for an elastic building-model, are achieved in many columns of the building-models, in the initial transient stage.One of unexpected fractures of structures due to the great Hanshin-Awaji earthquake is the fracture of a bridge bearing part of the Nielsen bridge type. The obtained numerical results show that a high stress sufficient to lead to a fracture appears in the upper part of the bridge bearing, when an impact of velocity higher than 5 m/s occurs between the upper and the lower parts of the bridge bearing.It is also illustrated that the maximum stress values occurred in the transient stage are strongly dependent on the size of the structure and the acceleration profile of the earthquake motion.In order to secure the inelastic energy absorptions capacity of structural members, the possibility of brittle fracture must be eliminated.Based on the full scale shaking table test, the ultimate energy absorption capacity of H-section beams influenced by the brittle fracture was minutely observed.A simple procedure to secure the ultimate energy absorption capacity is summarized as follows.1.Brittle fracture can be eliminated by detecting FTP condition through Charpy impact test of used materials.When2.FTP condition is satisfied, the ultimate energy absorption capacity can be estimated on the basis of tensile strength of materials.3.Since the inelastic deformation capacity of a member is proportional to the stress increase at the end of member, the efficiency in transmitting member's strength at the end of member (joint efficiency) must be adequately evaluated.