| Under the combined action of external load and lateral displacement,members of steel tubular scaffold often produce significant second-order effect due to that they are typical slender members.Meanwhile,upright and the horizontal tubes of steel tubular scaffold are usually connected by right angle fastener,bolt and other components,which induce obvious semi-rigid connection property and weaken joint strength between upright and horizontal tubes.As a result,it will increase the lateral displacement of steel tubular scaffold.The combined action of second-order effet and semi-rigid connection property often significantly affects the bearing capacity and deformation performance of steel tubular scaffold,and even cause various engineering accidents such as collapse.Therefore,it is necessary to develop analysis model of steel tubular scaffold taking into account the influence of both second-order effect and semi-rigid connection property.Meanwhile,in order to validate the analysis model and calibrate the design code of steel tubular scaffold,it is desirable to carry out the field test of steel tubular scaffold with different scaffolding erection height and different connection types.Hence,this thesis focus on the analysis model,field test and specification calibration of steel tubular scaffold.The main contents include:(1)Based on the differential equation of the beam-column element,the stiffness matrixes of the upright tube element involving the second-order effect and the horizontal tube element involving the second-order effect and the semi-rigid connection property were established respectively first.Then,an analysis model of steel tubular scaffold taking to account the second-order effect and the linear semi-rigid connection property was established based on the direct iteration method of nonlinear analysis.The accuracy and applicability of the developed analysis model was validated by comparing with the result of finite element analysis and experimental data of field test.Finally,the influence of the second-order effect and the linear semi-rigid connection property on the internal force and the displacement of steel tubular scaffold was quantitatively analyzed.(2)Based on the moment-rotation model describing the semi-rigid connection property of steel tubular scaffold,an analysis model of steel tubular scaffold taking into account the second-order effect and the nonlinear semi-rigid connection was established based on the stiffness matrixes of the upright tube element(involving the second-order effect)and the horizontal tube element(involving the second-order effect and the semi-rigid connection property)as well as the Newton-Raphson iteration method of nonlinear analysis.The accuracy and applicability of the developed analysis model was validated by comparing with the result of finite element analysis and experimental data of field test.Finally,the influence of the second-order effect and the nonlinear semi-rigid connection property on the internal force and the displacement of the steel tubular scaffold was quantitatively analyzed.(3)Field tests of the fastener steel tube full hall formwork support system,the high formwork support system of fastener steel tube and the keyway-quicklocked steel tubular formwork support system were carried out respectively.The experimental data of the internal force and the displacement of upright tube,horizontal tube and diagonal bracing were tested during the whole construction process(including formwork erection,concrete pouring,concrete maintenance,etc.).Based on the experimental data of the above filed tests,the developed analysis models were validated and the current design codes of steel tubular scaffold were calibrated. |
