Research On Axial Compressive Performance Of Masonry Walls Retrofitted By Prestressed Steel Strips

With the rapid development of Chinese economic construction,many buildings are facing the need of functional reconstruction and seismic capacity improvement.Bricks are used in more than 50% existing buildings in China as traditional construction materials.The proportion is more than 80% in rural buildings and cultural relic architectures.Therefore,the study of wall reinforcement in brick masonry structures has become a hot topic in the field of structure reinforcement research.The common reinforcement technology of brick masonry walls generally has the problems of stress lag,high demand of strength,involving wet work or nonreversibility.In consequence,this paper proposed the reinforcement method that using prestressed steel strips mainly fixed by the pull bolt which is dry connection.Experimental study and analysis of reinforced brick masonry walls with different longitudinal prestress levels were carried out.In this paper,an axial compression performance test of 11 reinforced brick masonry walls was conducted,with the layout of steel strips,the application of longitudinal prestress,the initial load level of walls and the strength of mortar as the study parameters.The failure characteristics of brick masonry walls and steel strips,the peak load,the change of displacement and the development of compressive strain of steel strips were all obtained.The test results show that the strengthening of brick masonry walls with the horizontal and vertical steel strips at the same time increases the peak load by 33%~43%.Applying the precompression stress in vertical steel strips can make the steel strips take part in work earlier and increase the cracking load of single brick in the wall.Applying the pretension stress in the transverse steel strips can exert the transverse restraint earlier,strengthen the lateral restraint of the vertical steel strips,and increase the peak load of the brick masonry walls by 10%.It also has great effect that retrofitting the brick masonry walls under load condition(the walls are not cracked)by prestressed steel strips.Based on the experimental study and results,the finite element model of prestressed steel strips reinforcing brick masonry walls was established by Abaqus and modified.Through further analysis of the variation factors such as level of vertical precompression stress,level of horizontal pretension stress and initial compressive strength of brick masonry walls,the discipline of the peak load of brick masonry walls reinforced by prestressed steel strips is obtained.With the increase of prestress in vertical steel strips,the peak load of specimens shows a downward trend.The level of horizontal pretension stress has little effect on the increase percentage of peak load.The lower the initial compressive strength of brick masonry walls,the better the reinforcement effect of steel strips.To sum up,the formula of axial compressive bearing capacity of brick masonry walls reinforced by prestressed steel strips is put forward and compared with the test results,which provides reliable reference for the promotion and application of this reinforcement technology in practical projects.