دانلود رایگان مقاله انگلیسی مدلسازی عددی و ارزیابی لرزه ای قاب های بتن مسلح میانقاب بنایی با پوشش های پلیمری - Sage 2018

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 One virtual five-story reinforced concrete frame was designed according to out-of-date Chinese codes.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.

Conclusion

The purpose of this study was to analytically investigate the effectiveness of varying CFRP retrofitting schemes in improving the seismic performance of existing substandard RC frames with masonry infills at high risk of collapse due to out-of-plane earthquake excitations. For this purpose, the IDA analysis was conducted for a typical five-story masonry-infilled RC frame before and after retrofit. Based on the analytical results, the following conclusions can be drawn:

1. For existing substandard RC frames, the collapse of masonry infills due to out-of-plane effect had a significantly adverse impact on the seismic performance of the structures. The mean maximum PGA and IDR capacities of the frame under earthquakes with different frequency contents were reduced by 30%–40%. The collapse of infills also resulted in that the plastic hinges were formed only in columns and the whole structure finally developed a softstory failure mechanism.

2. The earthquake frequency contents had an obvious influence on the maximum PGA capacity of structures. The maximum PGA resisted by RC frames increased significantly with the increase in A/V ratio of the ground motions. However, the structures’ IDR capacity changed little with respect to the change in the earthquake properties (A/V ratio). This confirms the availability and reliability of using the maximum IDR as a damage parameter to indicate the performance of structures.