The port facilities have been recognized as emergent supply transporting base in order to provide assistance for rehabilitation of disaster-affected areas. A system to evaluate the residual structural performance of the damaged facilities is required to judge whether the facility can be used or not. However, the method to evaluate the residual performance of earthquake-damaged piers has not been developed.
　This paper deals with damage process during earthquake and residual structural performance after earthquake of reinforced concrete (RC) superstructure of pier. Cyclic horizontal loading tests on the 1/4 scaled models of pier were carried out in order to clarify failure process of pier during earthquake. After cyclic loading tests, static loading tests on the RC beams of pier were conducted to clarify residual structural performance of the RC beams. The relationship between damaged level by earthquake and residual load carrying capacity was experimentally investigated.
　From the cyclic loading tests simulating earthquake, it was clarified that significant cracking and steel bar yielding occurred near the RC beam-steel pile junction. The residual load carrying capacity of the RC beam damaged by earthquake was above 60% of calculated non-damaged one even when the maximum horizontal displacement of pier reached 4 times of the displacement where the steel pile was yielded.