Cracking Mechanism Of Non Load Cracks In Steel Plate Concrete Composite Shear Wall During Construction

The frame core tube structure is usually used in super high-rise buildings to meet the requirements of structural strength,ductility,lateral stiffness and seismic performance.The steel plate concrete composite shear wall is usually used in the core tube structure.As a large-scale component,steel plate concrete composite shear wall belongs to the category of mass concrete,and in order to meet the needs of structure and construction,steel plate concrete composite shear wall usually uses high-performance concrete with high strength,high fluidity and good self compacting,but it also means that the cement consumption per unit concrete will be larger.Due to the large interface size and cement consumption,the composite shear wall will accumulate more heat in the wall during the construction period,which makes the early deformation of the wall too large.Moreover,combined with the early shrinkage of concrete,the internal stress of the wall will be large,which makes the wall crack risk.This paper first introduces the background and significance of the research,expounds the current research progress of early non load cracks in steel plate concrete composite shear wall,and then summarizes the causes of cracks in composite shear wall from three aspects of material,design and construction,and makes a detailed description of its influencing factors,and puts forward some measures to prevent cracks In order to explore the cracking mechanism of steel plate concrete composite shear wall,the temperature field,stress field and displacement field of the actual project are simulated by combining the basic theory of early stress of concrete structure and abaqys finite element analysis software.Through calculation and analysis,the main results are as follows1)After concrete pouring,under the joint action of hydration heat and heat transfer,the wall temperature rises rapidly,and then decreases slowly,resulting in temperature gradient inside and outside the wall;2)Under the combined action of temperature and shrinkage,the early external tension and internal compression of the composite shear wall,the tensile stress at the top of the inner side,the lower corner and the middle of the outer side of the wall may be greater than the tensile strength of the concrete at the same time,which makes the wall crack;3)Within a reasonable range,with the increase of the thickness of steel plate,the peak temperature and the peak tensile stress outside the concrete will decrease slightly,but it will aggravate the incompatible deformation between the steel plate and the concrete,and slow down the stress release of the wall,which is not conducive to the control of early non load cracks while reducing the tensile stress on the outer surface of concrete;4)The increase of wall thickness will increase the internal temperature peak value and internal and external temperature gradient of composite wall,increase the tensile stress on the external surface of wall,increase the incompatible deformation between steel plate and concrete,slow down the stress release of wall,increase the risk of wall cracking to a great extent,and control the wall thickness within the scope of meeting the specification and structural requirements.It can effectively reduce the risk of early cracking of steel plate concrete shear wall.5)Reducing the molding temperature of concrete can greatly reduce the stress value of composite shear wall,especially the effect of reducing the lateral tensile stress of concrete.Therefore,reducing the molding temperature of concrete is of great significance to control the surface cracking of steel plate concrete composite shear wall;6)The higher the strength grade of concrete,the greater the tensile stress peak value of composite shear wall.On the premise of meeting the bearing capacity and use function of the structure,the selection of high strength grade concrete will greatly increase the risk of cracking of steel plate concrete composite shear wall.