| In the construction process of super high,large span and other complex structural forms,super high formwork bracket system is an important construction security measures,and at present,the design specification of super high formwork bracket system in China is not perfect,lack of unified design standards,and lack of experience on the force state and construction points of super high formwork bracket system.In recently years,safety accidents caused by the overall collapse of formwork support systems have occurred frequently,so,the research on In recent years,safety accidents caused by the collapse of the whole formwork system have been frequent,so the research on the stability of the super-high formwork bracket system has become the focus of the industry.Therefore,the overall stability analysis and field test of the 60 m high plug-in self-locking steel pipe bracket and the reasonable optimisation of erection proposals are of practical significance for the design and erection of super high formwork brackets.In this paper,the study on the force characteristics and stability of 60 m high self-locking steel pipe supports was carried out based on a practical project in Xianyang City,with literature summary and theoretical calculations,field tests and finite element analysis methods.The main studies and findings are as following.（1）Firstly,the calculation principle of the plug-in self-locking steel pipe bracket was explained,and the theoretical calculation of the 60 m high plug-in self-locking steel pipe bracket system in a project in Xianyang City was carried out according to the code,and the distribution of the internal force of the bracket was obtained.（2）The model of the whole test frame was established by using finite element software to simulate the stress distribution and deformation trend of various types of bars under the construction load,and the eigenvalue buckling analysis and nonlinear buckling analysis were carried out for the whole frame.The nonlinear buckling analysis yields the entire brace at 81.03 k N.（3）The internal forces of the uprights,crossbars and diagonal bars of the 60 m high plug-in self-locking steel pipe bracket in construction were tested on site;the law of load distribution between the various types of bars was analysed.The results show that the stresses of the various types of bars are unstable,and the trend of their changes is mainly wavy,and the force situation is relatively complex,resulting in some of the bars being in tension;The comparison and analysis between the measured results and the simulation results show that the force law is basically consistent,and the results show that the assumed parameters are reasonable.In comparison with the calculation results of the specification,it was found that the maximum value of the measured stress of some of the uprights was greater than the calculated value of the specification,indicating that the results of the stability test of a single upright cannot replace the stability of the whole frame,and that reasonable construction measures need to be combined with the frame erection process to ensure the overall stability of the frame under construction load.（4）The finite element model was established to qualitatively study the laws of the number and mode of vertical diagonal bars,horizontal scissor bracing,lateral restraint,the length of the top horizontal bar projection of the uprights,and the height to width ratio of the frame.The conclusion of the practicality of the 60 m high plug-in self-locking steel pipe bracket and the correction coefficient of the calculated length of the vertical rod stability under different height to width ratios are given to provide valuable reference for the engineering practice,promotion and application of the ultra-high plug-in self-locking steel pipe bracket and the revision of the relevant regulations. |
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