| New-type precast diaphragm is a kind of precast assembly floor system,with high standardization level,fast erection speed and desirable technical economy benefit.In this paper,a method is proposed to use the new type of prestressed concrete hollow slab with the bi-axial reinforcement at the bottom of the plate.The prestressed tensile reinforcement is arranged in the orthogonal direction of the prestressed concrete hollow slab,connected with the component around by setting groove on the side of slab and stretching the prestressing tensile reinforcement and at the ends of slabs-the nodes of slab joints-stretched U-shaped steel reinforcement,and the prestressing tensile reinforcement;plugs are set in the hole of the slab ends to form new type of the floor system with the post-poured concrete.This paper begins with the research of the slab joints nodes of new type floor system and the introduction experiment of shear connectors is firstly performed,studying the mechanical property of shear connectors and the computing method of bearing capacity;after that,the study is conducted about the in-plane stiffness and deformation of the floor system,deducing the in-plane stiffness of new type floor system and the computing method of the strength and stiffness for the slab joints’ nodes.After that,the collapse-proof’s theory of the prefabricated new type floor system is brought up.Finally,the design method of the new type floor system and simplified seismic of its structural system is provided here.The main contents and results are as follows.(1)There are four kinds of shear connectors of new type floor system from series K1 to K4 designed.The introduction experiment of ten test specimens is conducted on the shear connectors under the combined action of in-plane shear and compression-shear.The paperstudies the failure phenomenon and the forced mechanism of the shear connectors.It analyses the main influences of the load-slip curves,the steel strain and the mechanical property of plate joint nodes as well as the shear principle of the plate joint nodes;at last,the loading model of the plate joint nodes is established and the proposed formula of bearing capacity is given to various forms of the shear connectors.The results show that the connection of the shear connectors of the series of K1 and K3 is reliable when the ratio range of the experimental value and formula calculation is between 0.80 and 1.70,the average value is1.378.(2)In this paper,the one-way cycling repeated loading and unloading is conducted on three precast monolithic floor specimens and it studies the failure phenomenon of the floor system.This paper analyses the performance index,including the relationship between load and deflection,relative slippage and stiffness degeneration coefficient;according to deep beam theory,the formula of in-plane deflection is derived and the computing method of in-plane stiffness new type floor system is discussed in this paper.The results show that the in-plane stiffness of precast new type floor system is about six times bigger than that of the common ones and the precast new type floor system made up of new type floor slab and post-pouring edge components has bigger in-plane stiffness and good integrity.Based on the plane cross-section assumption,the calculation formula of the plate joint nodes strength and stiffness is derived.(3)By using the method of removing the floor’s intermediate support,the anti-collapse experiment is performed on the two new type floor substructures with transverse joint nodes,studying the failure mode and crack development.This paper discusses the performance index like its bearing capacity,strain and maximum deformation and analyses the loading process of the floor system test specimens and suspension mechanism.In this experiment,the deformation mode of the floor structure is linear catenary.Compare the calculation formula of the bearing capacity derived from linear catenary mechanism with the experimental value,and the results show if the calculation value is a little smaller than the experimental value,it is a computing method which tends to be safe.The seam of precast new type floor system and the connecting structure of board side beam are reasonably arranged.The ideal anti-collapse capacity can be obtained by adopting proper peripheral and transverse seam connections.(4)The pseudo-dynamic test is carried on the structural models of the cast-in-place floorframed shear-wall and precast monolithic floor.It analyses the two structures’ displacement,acceleration,base shear response time-history curve,displacement response envelope diagram,hysteretic curve,inter-story displacement and storey stiffness under different working conditions.The curve of stiffness degradation is drawn and the concept of inter-storey shear force distribution has been brought up to tell whether the rigidity of the structural model’s floor system can meet the requirements.By calculation and analysis,it shows that both of two structures can’t be regarded as rigid floor,but both have good shear transmission capacity to guarantee the structural integrity.Prefabricated floor provide a scientific basis for the replacement of ordinary precast floor and post pouring surface or cast-in-place floor.(5)Based on the summarizing of the research status on new type floor seismic design,this paper puts forward the seismic design method of precast concrete new type floor.After that,according to the mechanical behaviors of prefabricated new type floor structure,it proposes the calculation model of using series-parallel-connection system and considers the in-plane anti-pushed rigidity of prefabricated new type floor in the model,calculating the influence the actual stiffness of new type floor in-plane has on the structural seismic response and internal force distribution.Finally,according to seismic design method of series parallel connection system,the analyses of numerical example are used for the experimental structure model of the new assembled monolithic precast floor.The results show that under the design intensity of seven degree and through the analysis and computation,the stiffness of the floor’s in-plane can be approximatively regarded as infinity. |
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