Study On The Bending Stiffness In Orthogonal Slab Laying Direction And Vertical Bearing Capacity Of DCNPD

Floor is a horizontal bearing structure system in building.The stiffness and vertical bearing capacity of floor directly affect the overall performance of building structure.The dead weight of the floor accounts for half of the total mass of the structure.The cost of the floor structure accounts for 20%-30% of the overall.Therefore,under the requirement of meeting the structural design value,choosing the floor with high bearing capacity,small dead weight and low cost can meet the economic efficiency of the building structure.At present,cast-in-situ reinforced concrete floor and composite slab floor with post-pouring layer have the advantages of good integrity and large structural stiffness,but there are wet on-site operation,which is not conducive to environmental protection,energy saving and emission reduction,and does not meet the development of modern building technology.The distributed connected new-type precast RC floor diaphragms(DCNPD)is composed of prefabricated floor and embedded connector,the bearing capacity of DCNPD is well,the elastic stage bearing capacity is equivalent to the cast-in-place floor,and the ultimate bearing capacity is higher than the cast-in-place floor.DCNPD has not laminated floor,which can effectively reduce the height of structure,reduce the dead weight of floor and reduce the proportion of floor cost,the construction of DCNPD is simple,there is not on-site pouring concrete,reduce carbon dioxide emissions,to achieve the industrialization of the building.The orthogonal slab laying direction(OSLD)and longing direction of DCNPD is made of the same material,but the structure is different.Due to OLSD existence slab joint,the stiffness of the structure is weakened in the transverse direction,and the stiffness of the joints is increased in the transverse direction.The stiffness of OLSD is inconsistent with that of the longing direction,so DCNPD is an orthotropic thin plate.The key and difficult point of this paper is to calculate the flexural stiffness in two directions,especially in OLSD.In order to determine the vertical bearing capacity of DCNPD,the calculation method of OLSD and the calculation method of vertical bearing capacity of floor are studied by combining finite element simulation and theoretical research.The main content is as follows:(1)The calculation method of DCNPD in OSLD is studied,and the numerical simulation of OSLD is carried out Based on the characteristics of OSLD,the precast slab torsion and slab opening are assumed,the simplified calculation model of OSLD is established,and the formula of equivalent OSLD is derived.The numerical analysis model of transverse plate was established,and the numerical simulation was compared with the theoretical value.Accordingto the numerical analysis model of transverse plate,the stress and strain changes of slab joints and concrete in the internal structure were studied,and the mechanism of transverse plate stress was revealed.It is found that the existence of slab joints will reduce the transverse stiffness,the joints will increase the transverse stiffness,and the influence of the number of slab joints on the transverse stiffness is more significant.(2)The vertical bearing capacity of DCNPD is simulated.The numerical analysis model of the whole floor is established,and the simulation value is compared with the test value according to the vertical force performance test of the floor to verify the accuracy of the numerical modeling method.According to the floor numerical analysis model,the stress and strain of the whole floor joint and concrete are analyzed,and the vertical stress characteristics of the whole floor are revealed.The result shows that the vertical bearing capacity of DCNPD is slightly smaller than the cast-in-situ floor in elastic stage,but much higher than precast floor without slab joint connectors,demonstrating that the connectors are effective in transferring the orthogonal slab laying direction(OSLD)force in DCNPD.(3)The vertical bearing capacity calculation method of DCNPD is studied.According to the bending differential equation of the orthotropic thin plate,the formula for calculating the bending stiffness of OSLD is substituted to obtain the analytical solution of the floor deflection and bending moment.The theoretical value is compared with the simulated value of the experimental value to verify the accuracy of the theoretical calculation.According to the DCNPD vertical bearing capacity calculation method,the sensitivity parameter analysis of the number of joints and the number of plate joints is carried out.It is found that the width of precast slab has the greatest impact on the bearing capacity of the whole floor.When the width of precast slab is within a reasonable range,the increase in the number of joints can appropriately improve the bearing capacity of the floor.In this paper,the flexural stiffness calculation method,vertical bearing capacity calculation method and numerical modeling method of DCNPD are of great significance to the analysis of the vertical force performance of the floor.The research results can provide references for the engineering application and architectural design of DCNPD.