Structural Behaviour Of A New-Type Assembled Hollow-Ribbed Floor System

As required by relevant national policies,prefabricated buildings are increasingly appearing in the whole country,which requires more technical support to make prefabricated buildings have the same mechanical behavior as or even better than cast-in-situ concrete structures.According to the current building characteristics and relevant requirements,this paper puts forward a new prefabricated hollow floor,which consist of flat roof and bottom plate,filled with foamed concrete blocks at the hollow place.The longitudinal bars of rib beams are welded and the plate bars are bonded during assembling,and the prefabricated plates are connected through post-cast strip.This floor system has longer span and smaller thickness than traditional floor.The static loading test of a one-half proportion single-span simply supported floor was taken,the deformation pattern,strain and crack development are recorded and analyzed.The new type of prefabricated hollow floor with simple fabrication process basically conforms to the requirements of engineering application.Under the ultimate test load of 12.67kN/m~2,the maximum deflection of the floor is 15.75mm(L/318),which is less than the deflection limit.The crack development at the bottom of the test floor is basically similar to that of solid floor.The anti-cracking performance of the floor is good on the whole,and the cracking load is larger than the standard regulation in normal use.The number and location of floor assemble joints affect the floor stiffness.Due to the influence of assemble joint,the bidirectional stiffness difference of the test floor is about 10%.Besides,the static tests of five floor panels with different joints were carried out.Through the analysis of the displacement,strain,bearing capacity and other parameters of five different plate members under vertical load,the conclusions are drawn as follows.All the members are subjected to bending failure under the vertical static load,and the strain along the section height of each member basically conforms to the assumption of plane section.Increasing joint strip width or the bonding surface roughness helps a little to reduce the negative influence on capacity brought by post-cast strip.However,the reasonable arrangement and quantity of post-cast strip position could greatly improve the bearing capacity and cracking load and weaken the negative impact of the post-cast strip.The finite element software ANSYS is used to model the test floor,and the results are in good agreement with the test results.The stress of rib beam is less than that of slab,and the floor support can be considered as simple support.By adjusting the geometric parameters of the floor system,it is found that the ratio of span to height has the greatest influence on the structure stiffness.In this paper,the bearing capacity of the new type of prefabricated hollow floor is analyzed by the analogue beam method and the plastic hinge theory,the calculation results show that the capacity calculated by analogue beam method is smaller than test results,because the method ignores the torsional stiffness and space work of the beam system.According to the location of the plastic hinge on the cross beam,the ultimate bearing capacity of the floor is obtained by using the plastic hinge method,considering the moment ratio of different libs by elastic method.The effective moment of inertia method is used to calculate the stiffness of the floor before and after cracking.The moment of cracking at different parts of the floor is obtained by considering the strength reduction of post-cast concrete.Besides,the cracking load at different positions of the floor is obtained,which is in good agreement with the test results.In this paper,the stiffness and vertical displacement of the structure at different stages are obtained.Furthermore,the dynamic characteristics of the new type of fabricated hollow floor are tested and analyzed.The influence of different design parameters on the fundamental frequency of the new floor system is analyzed by finite element software.The fundamental frequency of the structure is calculated by different ways and the simplified formula of the natural frequency is put forward.The experiment of pedestrian excitation on the floor found that the maximum acceleration response of the structure appeared in the center of the floor,and the influences of walking path,step frequency and number of people on the structure are analyzed.Finally,construction requirements and design suggestions for the new floor system.The process of components construction and assembling is put forward.