| Precast concrete sandwich plate is composed of concrete inner leaf,outer leaf,insulation layer and connector.It has the advantages of good insulation performance,easy to bury pipelines,fast construction speed,insulation layer and main structure with the same life,etc.,and is widely used in the exterior wall of prefabricated buildings.Concrete sandwich slabs can be divided into complete composite slabs,partial composite slabs and non-composite slabs according to the combination degree of inner and outer blades.The combination degree mainly depends on the shear transfer capacity of the connectors.The inner and outer blades of some composite panels have a certain combination effect.Compared with non-composite panels common in engineering,the thickness of inner blades can be greatly reduced,which reduces the weight of components,improves the installation efficiency and saves building materials.However,the current design standard of our country only recommends finite element method for internal force calculation,which lacks the theoretical calculation method of structural mechanics.Therefore,based on the homogenization of the connection layer,the analysis method of internal force and deformation of unidirectional simply supported sandwich plate is proposed through theoretical derivation,and verified by finite element analysis and test results.The main research contents and achievements are as follows:(1)Ignoring the effect of the substrate insulation material of the connecting layer.According to the mechanics of composite materials,the connection layer of precast concrete sandwich plate was homogenized,taking the V truss connection as an example,the elastic constants and constitutive equations of representative volume element of homogenized connection layer were obtained.(2)On the basis of homogenization of the connecting layer,The analytical solution of the interfacial stress of precast concrete sandwich plate under the action of temperature or out-of-plane load is derived.Thus,the most unfavorable section position and the theoretical calculation formula of internal force and deflection of the inner and outer blades of precast concrete sandwich plate under the action of temperature or out-of-plane load are obtained.The theoretical formula is verified by finite element software ABAQUS.The results show that the theoretical formula is in good agreement with the finite element analysis results.The maximum mid-span deflection of the inner and outer blades of some composite concrete sandwich plates increases with the shear stiffness of the connecting layer.The increase amplitude is small under the action of temperature,and large under the action of out-of-plane load.The internal force of the most unfavorable section under temperature is independent of the shear stiffness of the connecting layer.(3)The combination degree of precast concrete sandwich plate under external load was studied.According to the stress characteristics of non-composite slab and complete composite slab,the internal force and deflection of the slab are calculated.Combined with the expression of internal force and deflection of the slab under the action of outside plane load,the internal force combination degree and deflection combination degree of the slab are derived.The results show that the combination degree of concrete sandwich plate increases with the shear stiffness of connecting layer,and the combination degree of internal force is slightly greater than that of deflection,and the two can be converted to each other.The internal force and deflection of the inner and outer blades of the concrete sandwich plate can be deduced from the combination degree according to the axial tension and axial compression members respectively.(4)Summarize the results of plane bending test of precast concrete sandwich plate with unidirectional shear support at home and abroad.Taking the deflection combination degree as the representative,the experimental value of deflection combination degree is obtained and compared with the theoretical value.The analysis shows that the theoretical formula is practical and the calculation is more safe,which meets the requirements of engineering design. |
