Earticle

Many piloti-type RC buildings were damaged by Pohang earthquake. It is necessary to reflect the characteristics of domestic buildings and failure mode by an earthquake to the post-earthquake safety evaluation criteria. In this study, the behavior characteristics and failure mode of RC walls of piloti-type buildings subjected to eccentric axial load was investigated by the reversal cyclic test. The variables were the aspect ratio(height to length) of the wall and the eccentricity which was different because the axial force was applied at the same position from the center of the wall specimens. As a result of the experiment, the slender wall was dominated by the flexure behavior. On the other hand, flexure-shear cracks occurred predominantly in the wall with a small aspect ratio. The crack patterns in the positive and negative loading directions were different due to the influence of eccentricity. The number of crack increased, and the rotation of the wall increased while the maximum horizontal strength decreased when the shear moment and the eccentric moment acted in the same direction by the eccentric axial force.

As the frequency and scale of earthquakes in Korea increase, the government has enacted the risk assessment of earthquake-damaged buildings to quickly respond to earthquakes and prevent the spread of earthquake damage. Among the earthquake damage risk assessment contents, the risk of vertical structural members, such as columns and walls, is evaluated according to the damage assessment criteria for damage occurring on the surface of the member by structural type. Currently, the domestic damage evaluation standard of reinforced concrete(RC) wall members borrowed from Japan's damage evaluation standard, and there is insufficient reflection of the structural characteristics of domestic RC wall members such as piloti buildings and non-seismic details. Therefore, in this paper, based on the test results of RC wall members with different aspect ratios subjected to eccentric axial force, qualitative and quantitative damage evaluation criteria for wall members were derived. Specifically, the damage level of the wall member was divided into 5 stages, and qualitative evaluation criteria based on the visible damage conditions such as cracks, crushing and spalling of covered concrete, exposure, buckling and fracture of rebara, etc for each damage level and quantitative evaluation criteria based on the maximum residual crack width were derived. The damage evaluation criteria derived in this paper showed that some qualitative and quantitative evaluation criteria were smaller at the same level of damage compared to the existing domestic damage evaluation criteria.

Most reinforced concrete (RC) school buildings constructed in the 1980s have seismic vulnerabilities due to low transverse reinforcement ratios in columns and beam-column joints. In addition, the building structures designed for only gravity loads have the weak-column-strong-beam (WCSB) system, resulting in low lateral resistance capacity. This study aims to investigate the lateral resistance capacities of a two-story, full-scale school building specimen through cyclic loading tests. Based on the experimental responses, load-displacement hysteresis behavior and story drift-strain relationship were mainly investigated by comparing the responses to code-defined story drift limits. The test specimen experienced stress concentration at the bottom of the first story columns and shear failure at the beam-column joints with strength degradation and bond failure observed at the life safety level specified in the code-defined drift limits for RC moment frames with seismic details. This indicates that the seismically vulnerable school building test specimen does not meet the minimum performance requirements under a 1,400-year return period earthquake, suggesting that seismic retrofitting is necessary.