Study On Mechanical Behavior Of New Prestressed Steel-Wood Composite Column

Wood is a kind of natural and sustainable building material,with soft and warm texture,giving people a sense of comfort,in line with the aesthetic orientation of modern people;Steel has the advantages of high strength,light material,good ductility,and steel also has the advantages of economic saving and sustainable development,which can meet the long-term large demand for steel construction use.Traditional timber columns have some shortcomings,such as low bearing capacity,large cross-section area,easy to corrode and moth,etc.Therefore,it has become a new research direction to improve the mechanical properties of composite columns by adopting specific combinations of steel and timber.Based on this,this paper puts forward the concept of pre-stressed Steel-wood composite column,which uses circumferential pre-stressed steel to restrain the core timber column,gives full play to the high tensile properties of the steel,and the application of pre-stress makes the core timber column in the mechanical state of three-dimensional compression at the initial stage of loading,thus avoiding the stress lag on the steel.In the form of combination,the core timber column is longer than the steel.In the process of compression,the timber column first has a certain compression deformation,Increased deformability of wood under compression.When the composite force is applied,the steel and timber can coordinate the deformation.In order to study the mechanical properties of this new type of prestressing Steel-wood composite column,the following research work has been done in this paper:(1)Performance test of new prestressing Steel-wood composite columnsThe moisture content,density,compressive strength,tensile strength,flexural strength and flexural modulus of elasticity of wood were obtained through the material performance test of wood.According to the relevant provisions in the "Wood Structure Design Manual" [55],the strength index of wood was reduced,and nine parameters of wood as orthotropic anisotropy were given.The yield strength,ultimate tensile strength and elastic modulus of steel were obtained through the material performance test of steel.(2)Experimental study on bearing capacity of prestressed steel wood composite columnsThirteen prestressing steel restrained timber columns with different parameters were manufactured by prestressing steel with a self-made clamp device.Axial compression tests were carried out on thirteen prestressing Steel-Timber composite columns and one pure timber column.The experimental phenomena were described and the failure modes of the specimens were summarized.The reasonable combination form of steel and timber,i.e.the relative length of steel and timber,is explored.The factors such as bolt spacing,steel thickness,slenderness ratio and prestressing degree are changed.The mechanical properties,stiffness,ductility and energy dissipation capacity of composite columns are analyzed,and the optimal combination parameter form is given.(3)Study on Compression Theory of New Prestressed Steel-Wood Composite ColumnsReferring to the calculation model and reinforcing principle of FRP-confined concrete columns and timber columns,combining with the failure form of composite columns,the failure mechanism is analyzed,and the compressive constitutive model of concrete and timber is analyzed.The similarity between the two is pointed out.A new calculation model of ultimate strength and peak strain of prestressed Steel-Timber composite columns is proposed,and a stress-strain full curve model is proposed.The data demonstrate the rationality of the model.In this paper,13 pre-stressed Steel-wood composite columns and 1 pure wood column are tested under axial compression.The mechanical properties of composite columns are studied.The formulas for calculating ultimate strength and peak strain of composite columns are proposed,which can provide experimental reference and theoretical basis for popularizing the green Steel-wood composite columns in the future.