Study Of The Method To Estimate Elastic Deformation On The In-plane Of Un-topped Precast RC Diaphragm

In the total-prefabricated construction site concrete pouring can be avoid and construction speed can be improved effectively.Under the horizontal load,in-plane deformation will occur in un-topped precast RC diaphragm which is composed of precast floor slabs and metal connectors.The limited in-plane stiffness can’t make the diaphragm functions as a rigid partition between the vertical elements of the lateral force-resisting system.The in-plane stiffness is between flexible-diaphragm and rigid-diaphragm,a kind of limited-in-plane-stiffness-diaphragm.Existing code method is always based on assumptions for elastic mode shapes of structures with rigid diaphragms.Therefore,for structures with limitedstiffness-diaphragms,the diaphragm design forces calculated according to the code methods may not be appropriate.The floor diaphragm in-plane stiffness affects the building response in the following ways: the choosing of structural analysis model,the structural period,and the distribution of horizontal seismic action.In order to estimate the in-plane stiffness of un-topped precast RC diaphragm,a combination of numerical simulation and theoretical analysis is adopted in this paper.The main research objectives include the method to estimate elastic deformation,the method to build 2D finite element model.The main contents are as follows:Build the 3D finite element floor model,study on mechanical properties of diaphragm joints and in-plane deformation in the diaphragm.Mechanical properties in compression and tension of connectors are different.The compression stiffness is several time of tension stiffness,the value bases on the property of actual connection.According to the special connector mechanical properties three deformation model of un-topped precast RC diaphragm were proposed: 1)homogeneous beam model,2)rigid model,3)not-equal connector compressiontension stiffness model.Three corrections were made to the existing computing methods on the in-plane elastic deformation along slab laying direction: 1)each slab is assumed to be a rigid body without considering its deformation,2)the influence of not-equal connector compression-tension stiffness was taken into account,3)the actual load effect and length t of diaphragm was taken account.Study of the method to build 2D finite element model: 1)using compress-stiffness tensionstiffness tangential-stiffness to describe connector mechanical properties,2)using tensioncompression-spring to define the connector tension-compression stiffness,using tangentialspring to define the connector tangential-stiffness,3)setting the effective deformation of the spring.With benefit influence of connectors,a method to estimate elastic deformation in the transverse slab laying direction was proposed: 1)the computational model in the vertical direction was proposed,2)the calculation method was proposed.The study on the in-plane stiffness calculation of the un-topped precast RC diaphragm is of great significance for the establishment of the seismic design method for total-prefabricated construction.