Study On The Side Wall Joint Connection And Structure Mechanical Characteristic Of Prefabricated Multi-layer Underground Garage

With the aggravation of the urbanization process in China,the number of residents’ cars has increased dramatically with the problem of urban parking difficulty emerging.In the urban dense building complex,the soil resource is scarce,the ground space is limited.Because of the high space utilization and the convenient construction of the prefabricated underground garage,it provides a good idea to solve the problem of urban parking.In this paper,with the help of Chongqing Huimin branch prefabricated underground garage consulting project,the key problem of how to apply the prefabricated structure to the underground garage is studied.The main work of this paper is as follows:(1)This paper summarizes the construction technology of the prefabricated underground garage in the current urban dense buildings,which provides a reference for the promotion of the underground garage.In this paper,the influencing factors of the component division and the prefabricated system of the structure applied to the underground garage are studied.Combined with the structural functions and other factors,the modular design of the components of the prefabricated underground garage in Chongqing is carried out.(2)The paper analyzes the side wall connection mode of underground large space structure from the aspects of structure,force transmission mechanism and mechanical performance,and uses AHP model to compare and select the reasonable connection mode of the prefabricated underground three-dimensional garage side wall joint through calculating the matrix of bearing capacity,construction difficulty,damage ductility,cost of each connection mode and others.Combined with the mechanical properties and waterproof requirements of underground assembly structure,it is recommended that the side wall joint of the prefabricated underground garage should adopt the tenon joint through the prestressed reinforcement connection,and the position should be set at half of the side wall.(3)Through the theoretical derivation and qualitative analysis of the side wall joint stiffness,the influencing factors of the joint mechanical characteristic are obtained.The feasibility of numerical modeling is verified by existing test for the prefabricated side wall joint.Then,the bending characteristic of the tenon groove joint with prestressed reinforcement connecting is analyzed by numerical simulation.The influence of the spacing,axial force and section thickness of prestressed tendons on the flexural properties of joints is analyzed obtaining the relationship between rotation angle and bending moment and the relationship between joint opening and bending moment.Through the analysis of the shear properties of the joint,the influence of axial force,joint obliquity and the rigidity of the bonding layer on the shear bearing capacity and shear rigidity of the joint is studied.It is found that the axial force can significantly improves the shear bearing capacity and rigidity of the joint,and the obliquity of the joint improves the shear rigidity of the joint,but the shear bearing capacity declines.The rigidity of the bonding layer has a little effect on the shear bearing capacity and the rigidity of the joint.(4)A numerical model is established for the mechanical system of the structure using dual-purpose diaphragm wall.The mechanic and deformation characteristic of the key parts of the structure is studied under the different conditions of buried depth,thickness of the diaphragm wall and insertion depth.It is found that the reasonable buried depth of the structure is 4～6 meters,and when the thickness of diaphragm wall is up to 1 meters and the insertion depth increases to 1.2 times of the foundation pit depth,the influence on the uplift deformation and lateral displacement of the structure is no longer significant.