Experimental Research On The Mechanical Performance Of Precast Reinforced Concrete Shear Wall Base Isolation Structure

In the context of the national implementation of sustainable development strategy,prefabricated structure has become one of the effective means to realize housing industrialization,promote the concept of green building and green construction,and accelerate the structural adjustment and technological transformation of building industry in China.Compared with the traditional cast-in-place reinforced concrete structure,precast concrete structure is characterized by short construction period,less resource consumption,less environmental pollution,low labor cost and other advantages,which is the inevitable choice for the realization of sustainable development of construction industry.At present,shear wall structure has been widely used in high-rise structures owing to its good lateral force resistance.Prefabricated concrete shear wall will be widely used in residential buildings along with the development of housing and building industrialization.Nevertheless,the seismic design of prefabricated concrete structures is the same as that of cast-in-place concrete structures.Namely,it can increase the stiffness of structure,so as to make it not damaged under the action of minor earthquakes;on the other hand,plastic deformation will occur in the proper parts of the structure under the action of major earthquakes,so as to ensure the structure not collapsing by virtue of the structure's ductility to consume the seismic kinetic energy from the foundation.However,due to the strong randomness and unpredictability of earthquake,the actual seismic intensity may be much higher than the required design intensity,while the traditional design method cannot guarantee the design target of “no collapse under strong earthquake”.Base isolation is one of the most potential techniques to reduce structural damage under the action of strong earthquakes,which has been increasingly applied in seismic design and reinforcement maintenance of structures in earthquake regions for its good seismic reduction effect.Proper base isolation measures can be taken in prefabricated concrete shear wall structure,which can not only achieve good seismic reduction effect,but also avoid the above problems caused by the traditional seismic design methods.Especially for the high intensity regions,the base-isolated buildings will have obvious economic performance except for good seismic performance.Therefore,this paper studies the failure modes and mechanical properties of the base-isolated structure of fabricated concrete shear wall under the action of earthquake by means of low frequency cyclic loading.Through the numerical simulation analysis by using finite element analysis software ABAQUS,the influence of the rotation of isolation layer caused by the vertical deformation of isolation bearing on the seismic performance of the superstructure is studied.The main research contents are as follows:(1)For the high-rise concrete shear wall structure,the elastic analysis model was established by using PKPM and ETABS software,and the base isolation design analysis was made under the 8-magnitude design intensity;the design indexes of isolation structure all met the requirements of the specification limits.It provided the design basis for seismic isolation test substructure of prefabricated concrete shear wall.(2)The different crack developing rules,plastic development orders,failure modes,hysteretic curves,skeleton curves,energy-dissipating capacity,steel bar strain,isolation bearing deformation characteristics and etc.of three specimens,namely CSW-1,traditional cast-in-place anti-seismic coupled shear wall structure,PCSW-1,prefabricated coupled shear wall seismic structure with sleeve connection,and PCSW-2,prefabricated coupled shear wall isolation structure with sleeve connection,were investigated respectively by low cycle level load test.The test results showed that the deformation of isolation layer in the prefabricated concrete shear wall structure with sleeve grouting connection accounted for a major proportion in the total horizontal deformation,and isolation bearing served as the main dissipative member,so as to achieve the purpose of reducing superstructure damage,and effectively avoid sliding failure of upper prefabricated concrete shear wall structure at the joints,thus providing a superior energy-dissipating capacity.It provided a basis for the application and design of prefabricated shear wall isolation structure in the future.(3)On the basis of experimental research,the influence of vertical deformation of isolation bearing(rotation of isolation layer)on the lateral stiffness of superstructure was analyzed by ABAQUS finite element analysis software under the conditions of different concrete strength grades,different ratios of axial compression stress to strength,different height-width ratios,and different ratios of tensile and compressive stiffness of isolated bearing.The research results showed that the increase of concrete strength grade,the decrease in the ratio of axial compression stress to strength,the increase of depth-width ratio,and the decrease in the ratio of tensile and compressive stiffness of isolated bearing would increase the rigid body rotation degree of superstructure,thereby leading to the higher proportion of rigid body rotation displacement of superstructure in the total horizontal displacement,and making the lateral stiffness of base-isolated superstructure significantly lower than the anti-seismic model under the same conditions.