Stress Analysis Of Concrete Sandwich Roof Panel Under Temperature And External Loads

The concrete sandwich roof panel is a new type of roof panel system which integrates bearing capacity and thermal perfoemance.It is applicable for industrial production and provides important technical support for the realization of housing industrialization.Because of the temperature difference between inner and outer wythe of concrete sandwich roof panel is large,it will cause large temperature stress in inner and outer Wythe,and the coupling effect of external loads on the panel will have a significant impact on the performance of the panel.Thefore it is of great significance to study the coupling effect of temperature and external loads on the design and popularization of concrete sandwich roof panel.Firstly,on the basis of the existing theoreticeal calculation formula of temperature field,considering the creep and stress relaxation of materials in the period of temperature change,the temperatUre of concrete sandwich roof panels with different thickness in Changsha area under different working conditions is obtained.Secondly,the connectors is homogenized into a continuous sandwich layer,and the two-dimensional simply supported one-way panel is taken as the theoretical calculation model.The equilibrium equation of sandwich panel is established on the basis of basic assumptions and basic equation of panel elements.Considering the mismatch of curvature between inner and outer of sandwich panel,the geometric equation and compatibility equation are established.The differential equation of interface stress of concrete sandwich roof panel under the coupling action of temperature and external load is deduced by geometric equation,compatibility equation,equilibrium equation,geometric equation and compatibility equation.and the analytical expressions of interfacial shear stress and normal stress are obtained by boundary conditions.According to the boundary conditions,the analytical formulas of interface shear stress and normal stress as well as the intermal force values of inner and outer wythe and inner and outer wythe connectors of sandwich panel are obtained.Thirdly,finite element software ABAQUS is used to analyze and calculate the stress of concrete sandwich roof panel under the coupling action of temperature and external load,and the results are compared with the theoretical results.It is found that the results obtained by the two methods are basically consistent.The internal forces of the inner and outer wythe of the sandwich panel and the single connector in the panel are calculated by the equilibrium equation and isolation unit.Fourthly,the influencing factors of interface stress and internal force of inner and outer blades of concrete sandwich roof panel are analyzed by analytic solutions of theoretical formulas,and the results shows that the temperature effect can not be neglected,and the thickness of inner and outer wythe,the spacing of connectors and the stiffness of connectors are the important factors affecting the stress at the interface of the panel and the internal force of the inner and outer blades.Finally,the analytical solutions of interface stress,internal force and deflection of the inner and outer blades of the pre-stressed concrete sandwich roof panel under the coupling action of temperature and external load are obtained by theoretical derivation.It is found that the size of prestressing force is an important factor affecting the stress of the prestressing sandwich panel.