| With the rapid economic development in China,large-scale buildings,bridges and other landmark construction projects are emerging day by day,so the high formwork support has also been widely used.The coupler type steel tube scaffold has the characteristics of good practicability,simplified layout and removal,and high rigidity,so the basic component of high formwork is still steel tube and various couplers.However,the high formwork system is different from the ordinary coupler scaffold.It has the characteristics of high erection height,large erection span,heavy load,diversity and complexity.If there are unreasonable design,non-standard construction and other factors,it is easy to cause the overall instability of the scaffold system.In China,there is a lack of sufficient theoretical support in the calculation of high supporting formwork,a lack of understanding for the importance of defects,and a lack of attention in construction management.The collapse of scaffold happened again and again.Hence,we have to pay attention to the safety of high formwork in practical application and then reduce the accident risk in practical engineering application.In order to explore the potential risk of accidents of high formwork supporting system,this paper first makes a preliminary check on the strength,rigidity and stability of the beam and slab formwork of high formwork scaffold according to the current specifications in combination with the actual project.Then the characteristics of the existing coupler type node model were analyzed and commented on its application scope.The moment-rotation curve models describing the full-scale coupler type node of the mechanical behavior were selected in combination with the actual project.The full-scale high formwork scaffold three-dimensional finite element model is established by the "buckle" module of ABAQUS to analyze the stability of the system and to take into account the influence of an ideal rigid node model,a semi-rigid node model and a coupler looseness model.Finally,the single variable method is used to discuss the commonly used cross bridging in the actual project The lifting effect of diagonal bracing with wall connecting rod on the stability of coupler looseness scaffold.The main results are as follows:(1)The analysis of the whole stage mechanical properties of the joint shows that the coupler will loose in the early stage,and the rotational stiffness of the joint is close to zero.When the coupler and the steel tube are in close contact,it shows thesemi-rigid characteristics.(2)The finite element modeling analysis shows that the scaffold model considering the slack coupler tends to be "unstable" in the initial state,which greatly affects the safety of the high formwork scaffold.(3)The eigenvalue buckling analysis shows that the lattice diagonal brace has the best effect on improving the stability of the frame,followed by the wall bar and the diagonal brace;at the same time,from the analysis of the force displacement curve,it is found that the wall bar and the lattice diagonal brace can improve the resistance ability of the frame to defects,which has a certain guiding significance on how to improve the stability of the high formwork in the actual construction operation.In this paper,the mechanical properties,stability of the scaffold support system and the protection measures for coupler looseness are studied,and the suggestions for the design,erection and removal of the high formwork scaffold are given,which can effectively avoid the occurrence of safety accidents in the high formwork project.There are 50 figures,24 tables and 70 references in the thesis. |
