It is effective to apply hybrid damping device that combine separate damping device to cope with various seismic load. In this study, HRS hybrid damper(hybrid rubber slit damper) in which high damping rubber and steel slit plate are combined in parallel was proposed and structural performance tests were performed to review the suitability for seismic performance. Cyclic Loading tests were performed in accordance with criteria presented in KDS 41 17 00 and MOE 2019. As a result of the test, the criteria of KDS 41 17 00 and MOE2019 was satisfied, and the amount of energy dissipation increased due to the shear deformation of the high-damping rubber at low displacement. Result of performing the RC frame test, the allowable story drift ratio was satisfied, and the amount of energy dissipation increased in the reinforced specimen compared to the non-reinforced specimen.

The pipe for water supply is essential part among SOC (Social Overhead Capital) fields. Pipe for water supply is mainly damaged by deterioration of pipe, earthquake, ground sinking and so on. The leakage of water have been led to enormous economical loss in our country. The purpose of this study was to investigate the structural stability of flexible joint for relaxing impact due to earthquake and ground sinking. For this purpose, flexible joint was simulated using tensile load and internal pressure. As the results, flexible joint for structural stability was needed the tensile load of below 3 ton and internal pressure of below 60 kgf/cm2. However, it is considered that real flexible joint should be applied more high safety factor than that of simulation result because of combined stress.

The proposed hybrid damper installs at a coupling beam and consists of a high-damping rubber (HDR) and steel pin. The proposed hybrid damper adopted a pin-lock system acts as a viscoelastic damper under wind load (small displacement) while it behaves as a hysteretic damper under earthquake load (large displacement). In this paper, the pin-lock mechanism and structural performance of the proposed hybrid damper is evaluated through experiment. Experiments were carried out with the variables which displacement, loading frequency and steel pin quantities were used. Test results showed that the pin-lock mechanism and the performance of the hybrid damper under a large displacement were verified. Also equivalent damping ratios of HDR were increasing at a small displacement as displacement amplitudes were increasing. However HDR did not depend on frequency,

Structural damping includes material damping, friction effects at bearing and expansion joints, friction at bolted joints and mechanical damping by damper. There is not analytical basis for estimating the damping ratios. Structural damping ratios can be estimated by measuring forced vibration amplitude of a certain mode but it is almost impossible to vibrate the actual bridges to a certain mode by force. Therefore, RD technique utilizing a lot of ambient vibration data can be a practical method to estimate damping ratio. In this study, the damping ratio is estimated by analyzing the ambient vibration data of three steel cable stayed bridges.