Modelling and analysis of retrofitted and un-retrofitted masonry-infilled RC frames under in-plane lateral loading

Abstract

In the context of various developing countries where many old structures require retrofitting or strengthening work to mitigate earthquake hazards, a cost-effective method is the retrofitting of damaged masonry-infilled reinforced concrete (RC) frames using ferrocement overlays, and the strengthening of existing infilled RC frames with ferrocement. However, no reliable mathematical or computational tool is accessible in the open literature to estimate the effect of such a retrofitting technique quantitatively. The present study is a numerical investigation of the retrofitting effect of masonry-infilled RC frames using ferrocement. A finite element technique has been used effectively to develop a computational model for analysing bare RC frames, together with un-retrofitted and retrofitted masonry-infilled RC frames. The proposed model accounts for the material nonlinearities of both concrete and masonry, and the yielding of reinforcing steel. It is shown that the proposed model can be used effectively in predicting the load carrying capacity of existing RC frames, as well as the required degree of strengthening when ferrocement overlays are applied as a retrofitting scheme. A parametric study was performed using the proposed model on bare and infilled frames to quantify the effects of different parameters. This enabled the development of a simplified equation for predicting the ultimate load carrying capacity of masonry-infilled RC frames, which proved to be reasonably accurate and which was validated by both experimental and numerical results.