Numerical modeling and seismic evaluation of masonry-infilled reinforced concrete frames retrofitted with carbon fiber–reinforced polymer wraps

Abstract

This article investigates the efficiency of various retrofitting schemes using carbon fiber–reinforced polymers in improving the seismic performance of a substandard masonry-infilled reinforced concrete frame. One virtual five-story reinforced concrete frame was designed according to out-of-date Chinese codes. In total, 15 carbon fiber–reinforced polymers retrofitting schemes were adopted before earthquakes, and three sets of earthquakes representing low, medium, and high frequency contents were selected to conduct the incremental dynamic analysis. The influence of infills’ collapse due to out-of-plane effect was discussed detailedly, and then, the effectiveness of different retrofitting schemes was evaluated. It was found that the collapse of infills obviously reduced the seismic capacity and finally resulted in a soft-story failure mechanism for the reinforced concrete frame. For earthquakes with low frequency content, the enhancement efficiency of retrofitting infills or both columns and infills was increased with the increase in the number of retrofitted stories; however, for medium and high earthquake frequency contents, retrofitting infills or both columns and infills were inefficient when less than half of the structure height was retrofitted. Among the adopted 15 schemes, carbon fiber–reinforced polymers retrofit of both columns and infills along the full building height was found to be the most efficient. Improper selection of a retrofitting scheme could lead to the change of soft-story location. The inter-story drift ratio capacity of effectively retrofitted frames can meet the requirements of current seismic code.