In this study, RC frames with unreinforced masonry (URM) infill for typical school buildings in Korea are experimentally investigated to evaluate their seismic performance. For this purpose, one-bay, one-fourth scale specimens, with unreinforced concrete block (CB) infill having different boundary conditions due to beam rigidity, are tested under in-plane cyclic loading, using a distinctive measurement scheme consisting of three-axis strain gauges attached to all CB units. In this paper, the diagonal strut mechanism of CB infill including its main strut angle, average compressive strain, and equivalent strut width is discussed using principal compressive strains on CB units. The lateral strength carried by CB infill and RC frame from the overall response of the specimens is also explained, based on the compressive stress acting on the infill and the curvature distribution along RC members during the test.
SUMMARYThis study proposes a procedure for identifying spectral response curves for earthquake-damaged areas in developing countries without seismic records. An earthquake-damaged reinforced concrete building located in Padang, Indonesia was selected to illustrate the identification of the maximum seismic response during the 2009 West Sumatra earthquake. This paper summarizes the damage incurred by the building; the majority of the damage was observed in the third story in the span direction. The damage was quantitatively evaluated using the damage index R according to the Japanese guidelines for post-earthquake damage evaluation. The damage index was also applied to the proposed spectral response identification method. The seismic performance of the building was evaluated by a nonlinear static analysis. The analytical results reproduced a drift concentration in the third story. The R-index decreased with an increase in the story drift, which provided an estimation of the maximum response of the building during the earthquake. The estimation was verified via an earthquake response analysis of the building using ground acceleration data, which were simulated based on acceleration records of engineering bedrock that considered site amplification. The maximum response estimated by the R-index was consistent with the maximum response obtained from the earthquake response analysis. Therefore, the proposed method enables the construction of spectral response curves by integrating the identification results for the maximum responses in a number of earthquake-damaged buildings despite a lack of seismic records.
On October 15, 2013, a magnitude 7.1 earthquake severely damaged buildings on Bohol Island, the Philippines. This paper briefly reports on the typical damage to reinforced concrete (RC) buildings observed in the authors’ post-earthquake investigation. The current study focuses on the seismic performance of an earthquake-damaged building with exterior beam-column joint failure. Cyclic loading tests were conducted to propose a practical seismic strengthening method by installing RC wing walls for substandard moment-resisting frames with brittle beam-column joints. A scaled model representing the earthquake-damaged frame reproduced the damage to the exterior beam-column joint, which could not be evaluated using Japanese seismic evaluation methods because of an overestimation of the joint performance. Another specimen strengthened by the proposed method was successfully upgraded, forming a ductile beam yielding mechanism. The ultimate strength of the upgraded specimen estimated by the Japanese methods agreed well with the experimental results. The strengthening mechanism by wing walls was elucidated, knowledge of which will be useful for future applications to substandard buildings in developing countries.
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