The Experimental Study On Composite Beam Of Unsupported Steel-brick Masonry With External Prestress

With the increasing development of social economy,various industries are in the stage of rapid development,especially the current construction industry.Within the rapid development tendency of the construction industry,many old buildings such as the old city and the villages in the city no longer meet the living needs of modern people.Due to economic benefit,waste of resources,environmental pollution and other factors,it is unreasonable to completely rely on demolition and reconstruction.Therefore,an effective method is needed to reconstruct and reinforce old buildings to meet people's living needs.Nowadays,most of the old buildings are masonry structure which causes space limitation.The most important thing in the reconstruction and reinforcement of masonry structure is the technology of dismantling the wall underpinning.At present,the main underpinning methods have the problems of long construction period,large beam cross-section and poor appearance.This study raised the external prestressing and unsupported steel,masonry structure,can undertake composite construction first,then dismantle the lower bearing wallboard without supporting the upper structure,and does not require shuttering and wet operations.It has some advantages for instance simple construction,short time limit,safe and reliable,to keep the original construction layout and appearance.In this study,four composed beams were tested.Through loading each beam,the loaded-strain curve and loaded-deflection curve of each beam were obtained,and the mechanical properties and destruction mechanism of this composite beam under different external prestress were studied.The main contents and achievements of this paper are as follows:(1)by referring to relevant materials,this paper introduced the current status of the old masonry structure and the main reinforcement and renovation methods,and analyzed the significance and purpose of studying the reinforcement and renovation of the masonry structure.(2)through comparison of specimens without external prestress,it is concluded that external prestress has a significant effect on the improvement of ultimate bearing capacity of composite beam in masonry structure to contribute the bearing capacity up to 33%.(3)among the three external prestressed tensile methods,the single broken line method has better effect than the straight line method,while the double broken line methodhas the best effect on the improvement of the ultimate bearing capacity of the brick masonry composite beam specimen.The research results of this paper provide a theoretical basis and technical guidance for the reinforcement and renovation of old brick masonry,and provide valuable experience for the construction in the future.