A STUDY ON THE FAILURE OF RC PIER UNDER THE IMPULSIVE VERTICAL SEISMIC LOAD

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This research deals with a fundamental study on the damage of reinforced concrete (RC) column by the vertical earthquake load. First, the push-up apparatus was developed in order to reappear the circumferential crack phenomenon of RC pier in 1995 Hyogo-ken Nanbu earthquake. The followings were confirmed from the impulsive push-up experiments (1) Impulsive vertical motion during the earthquake could induce the circumferential crack of RC pier, (2) A circumferential crack was occurred by the tensile force due to the inertia force of negative acceleration and surcharge weight.Next, high-speed horizontal loading tests were performed on the damaged RC columns after the push-up impact test in order to examine the influence of circumferential crack on the strength and ductility. It was found that the ultimate strength and deformability of damaged specimens were about 10〜17% and 15〜40% less than undamaged specimens, respectively. Finally, the effect of various reinforcements (steel jacket, carbon fiber, etc) under the impulsive vertical load were examined, and recognized that fiber reinforcement could be the same effective as steel jacket reinforcement to the vertical earthquake load.