CSTF 내부접합공법으로 내진보강된 실물 철근콘크리트 골조의 내진성능 평가

Abstract

본 연구에서는 기존 강도증진형 내진보강법의 단점을 개선 및 보완할 수 있는 새로운 개념의 내진보강법인 Concrete-filled Steel Tube Frame (CSTF) 내진보강공법을 제안하였다. CSTF 내진보강법은 콘크리트와 강관의 장점을 최대로 활용한 공법으로서, 기존 골조와 보강재 접합부의 시공성 및 일체성을 혁신적으로 향상시켰다. 본 공법은 필요 내진보강량 산정이 간편한 전형적인 강도증진형 보강법의 일종으로서, 비내진상세를 가지는 전단파괴형 철근콘크리트 (R/C) 건축물의 내력을 손쉽게 향상 시킬 수 있다. 본 연구에서는 기존 한국 비내진상세를 가지는 R/C 건축물을 바탕으로 한 실물 2층 골조 실험체를 대상으로 유사동적실험을 실시하여, CSTF 시스템의 기존 R/C 골조에 적용 시의 내진보강효과, 즉 복원력 특성, 강성증진 효과, 지진응답 제어능력을 검증하였다. This study proposes a seismic retrofitting method using a concrete-filled steel tube frame (CSTF) system, a novel technique to improve the limitations of existing seismic strengthening methods. The CSTF method makes the most of the advantages of both concrete and steel pipes, thereby significantly improving constructability and increasing integration between the existing structure and the reinfoR/Cement joints. This method falls into the category of typical seismic retrofitting methods that focus on increasing strength, in which the required amount of seismic reinfoR/Cement can be easily estimated. Therefore, the method provides an easy solution to improving the strength of existing reinforcrd concrete (R/C) structures with non-seismic details that are prone to shear failure. In this study, a full-size two-story frames modeled from existing R/C structures with non-seismic details was subjected to pseudo-dynamic testing. As a result, the effect of the CSTF system, when applied to existing R/C structures, was examined and verified, especially as to its seismic retrofitting performance, i.e., restoring force characteristics, stiffness reinforcement, and seismic response control. The results showed that the RC frame with no retrofitting measures applied underwent shear failure at a seismic intensity of 200 cm/s², the threshold applied in seismic design in Korea. In contrast, in the frame retrofitted with the CSTF system, only minor earthquake damage was observed, and even when the maximum seismic intensity (300 cm/s²) that may occur in Korean was applied, small-scale damage was observed. These results confirmed the validity of the seismic retrofitting method based on the CSFT system developed in the present study.