Seismic Performance And Interaction Mechanism Of Infilled RC Frames Using New Masonry Blocks

With the implementation of the wall reform policy,new masonry has been widely used in the infill frame structure.However,the design provisions for infill reinforced concrete(RC)frames still extend the research results of solid clay brick-filled wall frames in the current design specifications.This dissertation studies the joint working mechanism of masonry and frame for four types of new masonry: hollow clay brick,concrete hollow block,aerated concrete block,and ceramsite concrete block.Through the test,the damage process and seismic performance of the full-scale infilled frame were studied,and the restrained masonry infill wall was separated by experimental means to analyze the mechanical behavior of the infill wall under different displacement angles.The simplified mechanical model of the new masonry infill wall is established,and the seismic performance of the integral structure of the infilled frame is analyzed by numerical simulation.(1)An experimental campaign comprising of seven full-scale masonry infilled RC frame specimens under low-cycle cyclic loading was conducted.The test parameters included: different infill-block types(hollow clay bricks,concrete hollow blocks,aerated concrete blocks,and ceramsite concrete blocks)and tying methods(local binding method,through-bar binding method,and reinforced-mortar binding method).From the experimental results,it was found that the infilled frame with aerated concrete blocks exhibited better integrity and anti-collapse capacity than that of other infilled frame specimens(hollow clay bricks,concrete hollow blocks,and ceramsite concrete blocks).On the other hand,the collapse resistance and energy dissipation capacity of the infill walls can be significantly improved either by adopting full-length or reinforced mortar tying methods.(2)In order to investigate the practical significance of presence of doors and windows,two full-scale infilled frames with wooden door and aluminum window were tested.During the entire experimental investigation,the likelihood of opening the door and window at different drift levels was evaluated.Due to the disintegration of infill walls,it was found that the wooden door became difficult to open corresponding to a drift ratio of 1/300.In case of frame with aluminum window,it was found that the aluminum window showed visible deformation corresponding to a drift ratio of 1/100,and experienced severe damage at 1/50 drift ratio.(3)To understand the infill-frame interaction,a novel test setup and loading protocol was developed to investigate the seismic behavior of the isolated confined masonry infill wall.Three full-scale confined infill wall specimens were tested under displacement controlled low-cycle cyclic lateral loading.The hysteretic behavior,stiffness and strength degradation,energy dissipation and deformation capacities of the confined infill walls at various drift ratios were investigated.Based on the experimental results and theoretical analysis,a simplified analytical model for the infill wall was established and empirical equations to estimate the stiffness of the infill wall were proposed.The reliability of the proposed models was verified against the experimental results.(4)A detailed non-linear static pushover analysis was carried out on the infilled RC frames using the analytical model and the aforementioned prediction models.Parametric analysis considering the influence of the block type,door/window location and irregular distribution of infill walls on the seismic behavior of infilled RC frames was studied.The influence of infill walls on the performance point related drift ratio,distribution of plastic hinges,and inter-story drift ratio were evaluated.