Research On Longitudinal Shear Capacity Of Cold-formed Thin-wall Steel Truss Floor Composite With Lightweight Mortar

Cold-formed thin-wall steel truss floor composite with lightweight mortar is a new –type of composite floor,which lightweight mortar is sprayed between the cold-formed thin-walled steel truss,and a certain thickness of self-leveling mortar is poured on the topping.This new-type of composite floor has better performance of thermal insulation,sound insulation,and integrity than traditional cold-formed thin-wall steel composite floor.In this paper,the shear performance of four full-scale size of cold-formed thin-walled steel truss-light mortar composite floors are studied,And the finite element analysis and theoretical research are carried out on the basis of experimental study.Through the four full-scale size of composite floors studying under monotone static loads,the failure process,bearing capacity and the failure mode are obtained.The results show that: 1)The failure mode of composite floor under the action of longitudinal is that the tapping screws are cut;after adding the tapping screw at the node,The failure mode of the composite floor is the steel crack at the junction of the upper chord and the web;2)The construction method of using a certain thickness of the polystyrene foam board instead of light mortar has little effect on the longitudinal shear capacity of composite floor;3)The longitudinal shear capacity of composite floor is increased by 23.02% when the self-tapping screws are added at the joints.Based on the experimental study,the longitudinal shear behavior of composite floor is simulated by ABAQUS finite element program.Based on the analysis of the finite element model,the influence of the number of screws,steel strength,steel plate thickness,light steel truss spacing and shear span ratio on the shear performance of the composite floor is analyzed.The study shows that:Light steel truss connection with enough screws can effectively ensure the strength of steel play;The strength of steel,steel thickness,shear span ratio,self-leveling mortar flange thickness of the composite floor have great influence on the shear capacity of composite floor;The effect of light steel truss spacing on the shear capacity of composite floor is small.The longitudinal shear capacity of composite beam can be divided into two parts,one part is providing by web member,which is decide by the shearing strength of the self-tapping screw,The other part is provided by combination upper chord,which is made up of flange plate and the upper chord,this part is related to the flange thickness of the floor,the thickness of the upper chord steel,the strength of the chord steel and the shear span ratio.The finite element simulation of 81 T-type composite truss beams are carried out,the finite element data of 81 groups are fitted using the calculation model of longitudinal shear formula for general type steel-concrete T-beam,the formula for calculating the contribution value of the composite chord on the shear capacity of the floor is obtained,the calculation formula of the shear capacity of T-type composite truss beam is obtained by superimposing the two parts,the results of the formula are in good agreement with the experimental and finite element results.By summarizing the research results of the cold-formed thin-walled steel truss-light mortar composite building in the early stage of the research group,combining with the studies of the shear of composite floor in this paper,the calculation method of cold-formed thin-walled steel truss-light mortar composite floor was obtained.