Study On Stability Bearing Capacity Of Disk Lock Steel Tubular Scaffold

The disk lock steel tubular scaffold for formwork has been applied in various construction projects,and has become one of the mainstream formwork supports due to its good integrity,high bearing capacity,convenient disassembly and assembly,and low construction cost.The stability bearing capacity is the main factor of the structural safety of the disk lock steel tubular scaffold which belongs to a thin-walled steel tube structure.On the basis of experiment and finite element numerical analysis,the semi-rigid characteristics of the joint,the mechanical properties of components in the whole process and the factors affecting the stability bearing capacity are studied.The main contents are as follows:(1)Six groups of components are randomly selected from construction site for the joint torsion test.By means of mathematical statistics,the two-parameter logarithmic function model of the joint torsional moment-rotation relationship is obtained.Combined with the numerical analysis of the solid finite element model of the joint,it is concluded that the contact area between wedge and disk plate and the strain hardening modulus of the material have great influence on the torsional stiffness of the disk-pin joint node.At the same time,a trilinear function model of the joint torsional moment-rotation relationship is given.The finite element numerical analysis of the test frame is carried out by using the single linear model,the trilinear model and the two-parameter logarithmic model respectively.The results show that the three models can meet the requirements of actual engineering precision.When two-parameter logarithmic model is used for joints,the numerical calculation value of the stability bearing capacity of the frame is the most consistent with the experimental value.(2)The loading tests were carried out for three working conditions.Load-Load effect curves were obtained,including load-frame lateral displacement,load-standing tube normal force,load-Horizontal tube end bending moment,load-diagonal brace normal force and so on.The test data show that the Load-Load effect curve in the buckling direction of the frame has typical non-linear characteristics,which can be divided into elastic stage,yield stage and buckling failure stage.The load at the end of the elastic stage is 0.7-0.8 times of the end of the buckling failure stage,and the load effect is 0.3-0.5 times of the end of the buckling failure stage.The value of the load at the end of the elastic stage divided by the material partial coefficients of the cold-formed thin-walled steel structure is reasonable as the design value of the stability bearing capacity of the frame.(3)The finite element models with different initial imperfection and different tension-compression stiffness of diagonal brace are numerically analyzed.The stability bearing capacity of the frame decreases linearly with the increase of initial imperfection.When the initial vertical imperfection of the frame is H/500 and the initial bending imperfection of the standing tube is L/1000,the numerical calculation value of the stability bearing capacity is most consistent with the experimental value.The stability bearing capacity of the frame increases non-linearly with the increase of the tension-compression stiffness of the diagonal brace.After the reduction coefficient of the tension-compression stiffness of the diagonal brace is greater than 0.05,the variation of the stability bearing capacity of the frame is very small,and the maximum variation range is 0.95%.When the reduction coefficient of the tension-compression stiffness of the diagonal brace is 0.03,the numerical calculation value of the stability bearing capacity of the frame is the most consistent with the experimental value.