Quasi-static Loading Test On Seismic Behaviors Of Two-story Brick Masonry Walls Retrofitted With Post-tensioned Tendons Between Stories

Masonry building is a traditional architectural form with a long history,and it is also the main building in the rural and urban areas.But in recent years,frequent earthquakes at home and abroad.Many earthquake disaster reports show that the masonry structure,especially the multi story masonry buildings,is most affected by the earthquake damage.In view of this,the scholars at home and abroad have done a lot of research on the reinforcement of masonry structure.There are relatively mature study of traditional reinforcement methods,but also a new type of prestressed strengthening masonry research.The research of prestressed strengthening technique is mainly retrofitting with post-tensioned tendons along the whole height of building.But in the actual project often encountered the phenomenon that a wall failures because of bearing capacity shortage.Therefore,it is necessary to further study the feasibility of retrofitting with post-tensioned tendons between stories.In this paper,quasi-static loading test on seismic behaviors of six two-story brick masonry walls were carried out.Compared and analyzed the mechanical behavior of unreinforced wall,masonry wall retrofitted with post-tensioned tendons between stories,masonry wall retrofitted with post-tensioned tendons along the whole height of building,masonry wall reinforced with steel mesh mortar surface method that under horizontal low cyclic loading.The horizontal load-displacement hysteresis curve,skeleton curve,stiffness degradation curve,energy dissipation and ductility performance,and other indicators of the masonry wall were studied to comparative analyze the seismic behaviors.On the basis of experimental study,the finite element software MSC.Marc is used to establish the accurate numerical model of the masonry wall,and the horizontal load is used to analyze the failure mode and seismic performance.The experimental results and finite element numerical simulation analysis show that:(1)the seismic behavior of external post-tensioned prestressed strengthening technique is better than that of steel mesh mortar surface method.Masonry wall reinforced with post-tensioned tendons is bending-shear failure mode.Cracks are carried out more and are relatively uniform.Material properties performance more fully,and the shear bearing capacity promotes more.The hysteresis loops are more full,and the area is bigger.Later stiffness degradation and energy dissipation performance better,however,the ductility performance is comparable.(2)MSC.Marc finite element simulation of the load-displacement single-push curve highly coincides with the test results of the skeleton curve.And the main tensile stress of the finite element model in the destruction is roughly similar to the fracture distribution and direction of the test wall when failure.(3)the effect of prestressed strengthening technique between stories is better than prestressed strengthening technique along the whole height of building.And the shear bearing capacity obtained by finite element simulation and variable parameter study are as follows:axial compression ratio 0.4 between stories＞axial compression ratio 0.2 between stories>W6>W5.This paper is part of the research project of Beijing Science and Technology Plan,"the research and demonstration application of key technology for the improvement of safety of construction and reconstruction of existing buildings(Z141100006014054)".And also this paper provides a theoretical reference for the popularization and application of the old residential in Beijing and the whole country retrofited with prestressed strengthening technique.