기존 RC 학교건물의 기둥 및 보-기둥 접합부에 대한 반복거동 평가

Abstract

As earthquakes continue to occur in Korea in recent years, the government is carrying out seismic evaluation and retrofit of existing school buildings. Most of the existing school buildings were built based on the old standard design. Therefore, if the structural characteristics of the column and beam-column joints on the standard drawing of the school building can be identified, it will be provide valuable data for detailed seismic evaluation of retrofitting. This study focus on the effect of the non-seismic details shown in the standard design of the school building through experiments on Reinforced concrete (RC) columns and beam-column joints. RC columns of existing school buildings are vulnerable to earthquakes because the hoops for transverse reinforcement are anchored using 90° hooks and widely spaced. In Chapter 3 of this thesis, experiments were conducted to evaluate the seismic behavior of RC columns with five full-scale column specimens with non-seismic details. The experimental results showed that the internal transvers crosstie had a significant effect in the non-seismic detailed column with a 90° hooks. In addition, due to the low axial force, the load-drift relationships, ductilities, and energy dissipation capabilities of column were not significantly affected by the the hoop spacing and anchor hook angle until the displacement ratio of 3.5% before failure. The evaluation model based on ASCE41-17 similarly predicted aspects of initial stiffness, maximum strength, and strength reduction after maximum strength. This study was based on the experimental behavior of single-column members and needs to be extended to the study of the frame structure in which the columns are connected to beams and slabs. In Chapter 4 of this thesis, a cyclic lateral load experiments conducted to evaluate the behavior of RC beam column joints present in school buildings. Eight full-size joint experiments were planned to analyze the eccentricity, presence of slabs, and the number of transverse beams.Experimental results showed that most experiments showed joint shear failure after beam yielding, and eccentricity reduced joint shear strength. The results of increasing the shear strength of the joints were shown by increasing the constraint effect on the inside of the joint part when the slab is present or the number of transverse beams increases. The results calculated based on ASCE 41-17 and the experimental results were showed substantial discrepancy because the guidelines for seismic evaluation of existing buildings did not take into account the number of transverse beams and presence of slabs when calculating joint shear strength. Therefore, for more accurate performance predictions, the actual three-dimensional shape of joints will have to be considered. Furthermore, based on the results of the follow-up studies, additional factors affecting joint behavior should be reflected in future relevant standards.