Experimental Study On The Bearing Capacity Of Imitation Wood Hollow Floo

Wood-like material is a new type of artificial glued laminated material with wood fiber as reinforcement and magnesium based cementitious material as matrix,which has light weight,high strength,good fire resistance,and strong resistance to salt brine corrosion.The research team used wood-like material as the board material to propose a hollow floor composed of orthogonal rib beams and covered with wood-like panels on the upper and lower surfaces,and conducted a series of mechanical performance studies on the floor.The research work carried out in this paper is one of a series of studies,mainly studying the mechanical properties of wood-like hollow floors under the condition of simply supported four sides.The research work and results are as follows:(1)The wood property test of the imitation board was completed,and the density,axial tensile strength,compressive strength,flexural strength,and flexural modulus of elasticity of the imitation board were obtained.(2)Five groups of 30 simulated wood panel specimens were designed and fabricated according to different span thickness ratios.By applying a locally uniformly distributed load at the center,the failure,crack patterns,and bending resistance of the simulated wood panel under four simply supported and four fixedly supported support conditions were studied,and the calculation formula for the bearing capacity of the simulated wood panel was proposed.The research results show that the types of cracks at the bottom of the board can be divided into two types under the action of uniformly distributed loads at the center of the board.The load-deflection curve of simply supported imitation wood on four sides can be roughly divided into three stages:linear elastic stage,strain hardening stage,and strain softening stage;The load-deflection curve of the imitation board fixed on four sides can be roughly divided into four stages:linear elastic stage,strain hardening stage,strain softening stage,and strain deadlock stage.The ultimate flexural capacity of simply supported and fixedly supported imitation wood decreases with the increase of the span thickness ratio of the imitation wood.Under the same span thickness ratio,the ultimate flexural bearing capacity of the four sided fixed supported imitation board is about 1.57 times higher than that of the four sided simply supported imitation board.Referring to the plastic hinge line method(yield line theory),a formula for calculating the ultimate flexural bearing capacity of simply supported and fixedly supported imitation wood panels on four sides is established,and a crack correction coefficient is proposedβThe formula was modified,and the corrected theoretical calculation value was in good agreement with the experimental value.(3)Through similar analysis,a 1/2 scale model of 2000m×2000m wood imitation hollow floor is designed and made.Through the uniform loading test,the co-working condition,load-strain curve and load-deflection curve of the cladding panel and the rib-beam of the floor are studied,and the natural vibration frequency of the floor is measured.The results show that the floor deformation is similar to"bowl shape"under uniform load.When the load value is 4k N/m~2,the mid-span deflection value of the floor is 5.80mm,which is 1/322 of the span,meeting the provisions in the relevant specifications that the maximum deflection value of the floor under the normal use limit state shall not be greater than 1/250 of the span.The stiffness of the floor structure in two vertical directions is different,mainly because the short-ribbed beams are connected and fixed by steel connectors,resulting in the joint stiffness reduction,resulting in the stiffness difference between the two vertical directions.Under the action of 1.5 times design load,no obvious damage occurs to the floor structure.At this time,the mid-span deflection value of the hollow floor is 13.07mm,which is 1/143 of the span,indicating that the floor integrity is good.The existing relevant codes are conservative in the design of wood structure.The cross beam system method is used to check the bearing capacity of the imitation wood hollow floor.The experimental values are in good agreement with the theoretical calculations.The first order natural vibration frequency of the floor model structure is 20.7Hz.The first order natural vibration frequency of the prototype structure is 14.64Hz,which meets the requirement of natural vibration frequency of the floor in relevant specifications.(4)The theoretical analysis and calculation of the bearing capacity failure test results of hollow floors using the cross beam system method,the two-way plate method,and the pseudo plate method show that the floor structure in this paper is closer to the grid floor structure,so the deflection value calculated using the cross beam system method is in good agreement with the test value,with an error value of 6.6%.;The error between the theoretical calculation value and the experimental value of the two-way plate method is the second,with an average error of 22.08%;The error between the theoretical calculation value and the experimental value of the pseudo plate method is the largest,with an average error of 25.04%.Among the three methods,the theoretical calculation results of the cross beam method are the closest to the experimental values,and it is recommended to use the cross beam method as the theoretical calculation method for the imitation wood hollow floor.