| With the complexity of building function requirements,large spatial structure forms are emerging,and the diversification of spatial modeling has brought technical problems to the construction,which put forward new requirements for the formulation of safe and stable construction scheme of high formwork support system.High formwork support system refer to the formwork support system of concrete members in construction site with formwork support height more than 8 m,span more than 18 m,total construction load more than 15 k N/m~2,or concentrated line load more than 20 k N/m.Disc-buckle type formwork support overcomes the shortcomings of traditional fastener formwork support,such as easy to loss of fasteners,has the advantages of fast installation and strong self-locking ability,so it is widely used in high formwork support system.Due to the lack of thorough understanding of the stability calculation theory of the high formwork support system and the imperfection of the theory,the technical personnel rely more on the construction experience for the formulation of the construction scheme,which leads to frequent accidents.Therefore,it was of great significance to study the safety and stability of the disc-buckle type high formwork support system to reduce the frequency of accidents and ensure safe construction.Theoretical analysis,laboratory test and numerical simulation were applied to the study of the performance of the disc-buckle type formwork support.Combined with the construction requirements,the correction method of the effective length correction factor with the lateral frame column theory was proposed.The material properties,bending capacity of joints and overall stability of the disc-buckle type formwork support were systematically studied,and the influence law of relevant parameters on the overall stability of the disc-buckle type high formwork support system and the stability law of the variable cross-section high formwork support system in practical engineering were mastered.The main research contents were as following:(1)Based on the semi-rigid theory of joints,the semi-rigid characteristics of disc-buckle type formwork support were verified by the semi-rigid judgment criterion of socket joints.Based on the theory of sway frame column and considering the constraint of horizontal bar,i.e.,the semi-rigid characteristics of the joint,the three-dimensional cloud diagrams of the effective length correction factor were obtained by MATLAB programming.The influence of setting parameters,joint bending stiffness,section size and material properties on the effective length correction factor was systematically studied.The value area and specific factor of the effective length correction factor of different setting parameters were determined to realize the optimization design of the setting scheme.(2)The joint bending capacity and shear capacity of the disk-plate of the disc-buckle type formwork support were experimented to obtain the accurate numerical model of the joint of the disc-buckle type formwork support.The correctness of the finite element model was verified through the comparative analysis of the experiment and the finite element.Based on the accurate finite element model of the joint,the parametric analysis of the influencing factors such as the depth of the wedge insertion the disk-plate,the initial position of the wedge insertion the disk-plate,the thickness of the wedge,the material constitutive of the wedge and the thickness of the disk-plate was carried out to master the influence law of the relevant parameters on the joint bending performance.As found that the connection joint of the disc-buckle type formwork support is a typical semi-rigid connection joint.The thickness of the wedge,the material constitutive of the wedge and the thickness of the disk-plate have the most significant influence on the bending behavior of the connection joint of the disc-buckle type formwork support.The drop depth of the wedge should not exceed 6mm during the locking process,the most suitable thickness of the wedge was set to 7mm,the most suitable thickness of the disk-plate was set to10mm and the most suitable yield strength of the wedge was set to 450-500MPa.(3)The material properties,bending capacity of joints and overall stability of the disc-buckle type formwork support were studied by experiments.The influence parameters of working conditions,lift height,vertical diagonal bracing and sleeve on the structural stability bearing capacity was mainly considered.The regularity of the buckling direction of the vertical pole,the stress at each typical position on the vertical pole and the axial force of the vertical pole was studied.The results showed that reducing the lift height and arranging the vertical diagonal bracing have remarkable influence on improving the structural stability bearing capacity,and the usage of sleeves has little influence on the structural stability.(4)Through parametric analysis of influencing factors such as joint bending stiffness,structural parameters,setting form and spatial arrangement of vertical diagonal bracing,the influence law of relevant parameters on the overall stability of high formwork support system was mastered.The results showed that the lift height and the joint bending stiffness have the significant influence on the overall stability in the setting parameters.Whether the long strip or strip of the disc-buckle type high formwork support system,along the two directions set vertical diagonal bracing was more conducive to the overall stability,the vertical diagonal bracing was set on the periphery of the support system,which has significant effect on improving the overall stability bearing capacity.(5)Through the finite element analysis of the stability bearing capacity of the variable cross-section disc-buckle type high formwork support system with special structure in practical engineering during the construction period,the stability bearing capacity and deformation law of the variable cross-section disc-buckle type high formwork support system in the construction process were revealed.Through parametric analysis of the influencing factors such as the joint bending stiffness,the setting parameters and the initial imperfection,the influence law of the relevant parameters on the overall stability of the variable cross-section disc-buckle type high formwork support system was mastered.The result showed that when the long strip variable cross-section disc-buckle type high formwork support system was subjected to ultimate load.The corner pole position at the higher variable section and the lower variable section of the weak stiffness direction support system were prone to instability failure.The overall stability bearing capacity was mainly affected the lift height,and vertical diagonal bracing play an important role in improving the overall stability. |
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