Research On The Calculation Method Of Initial Imperfection About High Formwork Support With Couplers

The fastener-style steel pipe formwork support system has already found awidespread application in long spans and the extra-high building construction. Forsemi-rigid connection and erection parameters, researchers make some in-depth studieson the ultimate bearing capacity of the steel tubular scaffold with couplers, but a largenumber of formwork collapse accidents still do happen, all these indicate that currentresearch cannot satisfy the practical need of engineering. This paper will take initialimperfection in high formwork support with couplers as the main research object.Classifying initial imperfection which exists in high formwork support system,discussing the influence of these factors on the ultimate bearing capacity of the steeltubular scaffold with couplers by finite element analysis (FEA). and making contrastiveanalysis on the calculation methods about initial geometric imperfections. Finally, forthe application of this calculation method in engineering, we develope the calculationprogram by MATLAB and ANSYS.The main works and research results of the paper are as follows:①The paper will classify initial imperfection of the steel tubular scaffold withcouplers by mechanical defects, material defects, erection parameters deviation andinitial geometric imperfections, Establishing finite element model about formworksupports system and doing the linear and non-linear buckling analysis by ANSYS. Withthe stiffness of semi-rigid connections increasing, comparing with rigid frame andflexible framework, the ultimate bearing capacity of the steel tubular scaffold withcouplers will decrease by more than85%; When wall thickNess of steel pipes isdecreased from3.96mm to3.24mm, the ultimate bearing capacity will decrease byabout6.66%; When the value of initial geometric imperfection（R）is increased from5mm to20mm, the ultimate bearing capacity will decrease by about15.32%; Therefore,Mechanical defects, material defects and the initial geometric imperfection havesignificant influence on the ultimate bearing capacity of the steel tubular scaffold withcouplers.②With semi-rigid connections, researchers make in-depth theoretical analysisand testing studies on fastener-style steel pipe formwork support system, So this paperconsider semi-rigid connections in finite element model directly. and introducing themethod for finite element modeling (FEM) with some of the parameter settings. ③With semi-rigid connections in finite element model，the second chapter of thepaper discusses the influence of material defects and erection parameters deviation onthe ultimate bearing capacity of the steel tubular scaffold with couplers by ANSYS-PDS,Among these influencing factors, the result shows that wall thickNess and outerdiameter of steel pipes，lift height have a a great influence on ultimate bearing capacityof the steel tubular scaffold with couplers，especially steel tube wall thickNess. Thereby,the paper recommends modifying the stability design formula by a correction factorbased on measurement data from the construction site.④There are many ways of taking geometric imperfection effects into account.Three methods of modeling imperfections were trialled in，including the scaling ofeigenbuckling modes, the application of notional horizontal forces, and the directmodelling of initial geometric imperfections. All three methods were found to givesimilar results in the nonlinear analysis when applied in the modelling. andcorresponding parameters for three calculation methods have been determined by thestandards based on relevant specifications.⑤Finally, The human-machine operation system for the fastener-style steel pipeformwork support system based on ANSYS and MATLAB GUI is developed, With thehuman-machine operation system，the calculation method of initial imperfection can beapplied in high formwork support with couplers. it can offer technological support onthe calculation of ultimate bearing capacity for the builders in the construction site.