Analysis On Stability Bearing Capacity And Reliability Of Fastener-style Steel Tube High Falsework

With the rapid development of our country’s social economy,more and more tall spatial structures need to use high falsework.At the same time,the collapse of the falsework system has occurred frequently,which has brought huge damage to people’s lives and property.Therefore,the research on the safety and reliability of the high falsework has far-reaching theoretical value and engineering significance.In this paper,the finite element software is used to study the stability bearing capacity of the high falsework under various parameters,and the reliability of the high falsework system is analyzed based on Response Surface-Monte Carlo Method and ANSYS PDS Monte Carlo Method.The main research contents and results are as follows:(1)The finite element simulation analysis of the rotation test of right-angle fasteners is carried out through the finite element software ANSYS Workbench.In the fasten joint,the cover plate of the right-angle fastener near the bolt yielded first,and the stress at the connection of the cover plate and the base is also high.This is consistent with the test results and engineering practice.The values of M and θ under the tightening torque of the three sets of bolts are also obtained from the analysis.By using MATLB,a quadratic polynomial nonlinear model is used to perform nonlinear regression on the relationship of three groups of fastener bending moments with rotation angle under different tightening torques,and three groups of T and Rk values are obtained.Then the relationship between the bolt tightening torque T and the initial rotational stiffness Rk is linearly regressed by using the two-parameter linear model,and the relationship between them is obtained.(2)The finite element software ANSYS is used for parametric modeling,the force analysis of the falsework is carried out,and the stress status of the members is understood through the axial force analysis and the stress analysis.The initial defects such as initial bending and corrosion of the vertical bars are simulated by applying horizontal virtual loads,and the non-linear buckling analysis of the falsework system is performed to obtain its stability bearing capacity.The accuracy of the model is verified by detailed comparison with the prototype test results.At the same time,the influence of the erection parameters on the stability bearing capacity of the falsework system is also studied,and it is found that the presence or absence of vertical X-bracing has a great influence on the stability bearing capacity of the falsework.The stability bearing capacity of the falsework with vertical X-bracing is more sensitive to the change of the vertical bars’ spacing,and the stability bearing capacity of the falsework without X-bracing is more sensitive to the change of the distance of the horizontal bars.When the height of the sweeping bars of the falsework and the top extension length of vertical bars exceed a certain value,its stability bearing capacity will be greatly weakened.In actual engineering,the limits of these two parameters should be strictly controlled.(3)Through the statistical analysis of the measurement data of the steel pipe wall thickness,outer diameter,and sweeping bars height measured on the construction site,the statistical characteristics are obtained.By consulting the literature at home and abroad,the load probability model of the high falsework is established and the appropriate statistical characteristics of the constant live load during the construction period are selected.Then,according to the statistical characteristics of the integrated reliability influencing factors,the sensitivity analysis of the high falsework is carried out.Based on the results of the sensitivity analysis,the ultimate bearing capacity expression is fitted based on Response Surface Method,and the probability model of resistance of the high falsework is obtained.Finally,the limit state equation of the high falsework is obtained,and the failure probability of the high falsework is calculated by Monte Carlo Method.Then the results are compared with the results calculated based on ANSYS PDS Monte Carlo Method.The results obtained by the two methods are very close,indicating that the quadratic polynomials without cross terms used in this paper can better fit the ultimate bearing capacity expression of the falsework,and using Response Surface-Monte Carlo Method can greatly improve the calculation efficiency and reduce a lot of calculation time.Finally,this method is applied to the actual project to analyze the reliability of the high falsework system erected in a project in Guangzhou.