Masonry infilled reinforced concrete frames retrofitted with vertical post-tensioned bars
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Date
2016
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
Reinforced concrete (RC) frames filled with clay brick walls are among structures that have been damaged in many past earthquakes. The main aim of this study is to propose a new retrofit method, which can increase lateral strength, stiffness, energy dissipation capacity and ductility of infilled RC frames. To achieve this aim, at first seismic behaviour of several bare and infill RC frames were studied through experimental and numerical studies. Then the proposed retrofit method which was based on external post-tensioning of infilled frames by vertical bars was developed. Finally, the effectiveness of the proposed retrofit method was evaluated through experimental test. In the test, a total eight RC frames with two different aspect ratios of 0.5 and 1.0 were constructed with the scale of 1:3. Experimental test was performed using a quasi-static cyclic loading. For all experimental test, the values of initial lateral stiffness, effective stiffness and ultimate lateral strength were determined. The ductility and energy dissipation capacity were calculated using hysteresis curve obtained from cyclic loading. Results indicated that the presence of brick walls reduced the ductility of bare frames. Ductility of bare and infill frames are dependent on the aspect ratios. Bare frames with the higher aspect ratio has 70% higher ductility compared to that of lower aspect ratio. Failure mode of frames was also dependent on the aspect ratio. The presence of brick walls increased three and half times the energy dissipation capacity of the frame with higher aspect ratio. The proposed posttensioning method increased ultimate lateral strength and ductility of infilled frames two and five times, respectively. Increase in the ultimate lateral strength of infilled frames was dependent on their aspect ratio. Increase in the ultimate lateral strength of the frame with lowest aspect ratio was three times more than that of highest aspect ratio. Similarly, the ductility of retrofitted frame with the higher aspect ratio was 45% more than that of lower aspect ratio. The post-tensioning method increased the energy dissipation capacity of retrofitted frames. The retrofitted frame with higher aspect ratio dissipated 10% more energy compared to the frame with lower aspect ratio. The proposed retrofit method using post tensioning improved ductility, energy dissipation capacity and ultimate lateral strength of infill frames with opening. However compared to fully infill frames without opening, the rate of improvements was slightly lower. In general, results of experimental and numerical studies in this research showed that post-tensioning can improve stiffness, ductility, ultimate lateral strength and energy dissipations capacity behaviour of infilled RC frame.
Description
Thesis (PhD. (Civil Engineering))
Keywords
Reinforced concrete—Testing, Buildings—Retrofitting, Earthquake resistant design