Research On Bending Performance Of Cold-formed Thin-walled C-shaped Steel-Paper Straw Board Composite Floors

In recent years,green buildings have been widely advocated and recognized,and gradually applied in the world.Light construction materials currently researched and put into use in China include lightweight concrete,oriented strand board,bamboo plywood,gypsum based self-leveling mortar,and so on.With the improvement of people’s awareness of living environmental protection,a new type of green building material derived from crops,straw board,came into being.The straw board has the characteristics of high strength,excellent energy conservation and heat preservation,economic and environmental protection,and good fire resistance.The research of the light-weight composite component with straw board as the cladding panel can give full play to the respective advantages of different composite materials.It can not only make use of agricultural straw resources,reduce environmental pollution,but also conform to the new urbanization concept.A new type of composite slab is proposed,which is composited of paper straw board and cold-formed thin-walled steel with self-tapping screws.The bending test of three composite floors was carried out,and the influence of different steel beam section sizes,spacings and the number of screws on the bending performance of composite floors was studied.Observe the change trend of the deflection of the composite floor,observe the failure process and form of the composite floor,investigate the combined effect of the composite floor,and obtain the bending capacity of the floor.The results show that the ultimate failure mode of the composite floor is the local buckling of the cold-formed thin-walled steel beam due to the sufficient constraints of the straw slab,and the reduction of the screw spacing has an impact on the bending capacity of the composite floor.The finite element software analysis ANSYS was used to carry out numerical analysis on the bending performance of the composite floor under the condition of both sides support and simple beam end support.The constitutive relationship between steel and straw slabs was modeled by linear elastic model,shell element was used to simulate steel and straw board,and spring element was used to simulate the connection between the cladding and the steel skeleton.The results of the finite element method were basically consistent with those of the test,which proves that the finite element method was reasonable and feasible,and uses a reasonable finite element model for subsequent parameter analysis.By comparing the vertical deflection value of the composite floor with that of the corresponding finite element model,the spacing of the steel beam,the span of the composite floor and the thickness of the steel on the bending performance of the composite floor are analyzed.The analysis results show that the bending capacity and mid-span deflection of composite floor can be improved by reducing the spacing of the steel beams and the span of the composite floor,and increasing the width of the composite floor and the thickness of the floor panel.Based on the integral elastic members and assumed condition,the theoretical calculation of composite floors was carried out,and the formulas of the deflection and the bending capacity of the normal section of the composite floor were obtained.In the normal use stage,the error between the formula to calculate the mid-span deflection of the composite floor and the test value was within a reasonable range.The steel beam yields when the composite floor was damaged,the change of the strain value of the straw board and the steel beam was basically the same,and the test value and the theoretical value of the flexural capacity of the normal section of the composite floor were in good agreement.The calculation formulas of the deflection and bending capacity of the composite floor proposed in this paper are feasible.Compared with other forms of light-weight composite floor,the cold-formed thin-walled C-shaped steel-paper straw board composite floor has better deformation capacity and bending capacity,which can meet the design requirements of light-weight floor.