Design Study Of Assembled Internal Support Structure

In view of the advantages and disadvantages of reinforced concrete internal bracing and steel bracing support in existing foundation pit projects,based on the concept of green construction and the requirements of construction space,this thesis proposes a recyclable and reusable prefabricated internal support structure,which is composed of standardized components such as steel truss beams,steel support connection nodes and vertical support columns.And all the components are prefabricated in the factory,ready to install,and can be applied to various foundation pits,which is safe,environmentally friendly and convenient.This thesis studies the component composition,combination form,design calculation,and working characteristics of the internal support structure.The major operation and positive are as below:(1)The proposed prefabricated internal support structure is mainly composed of steel truss girders and steel brace join nodes.Different shapes of internal support structures can be formed through different connection methods of steel brace beams and join nodes,different shapes of internal support structures can be formed,which can meet the needs of foundation pit projects with different planar shapes.(2)To design and calculate the inner support components,first determine the size and material of the members based on project experience,then use the knowledge of steel structure to calculate the bearing capacity of the members and nodes,and finally determine the form of the support components.(3)ABAQUS finite element software is employed to construct a prefabricated internal support foundation pit support model,thereby revealing the variation pattern of the support structure throughout the excavation process.Initially,as the excavation depth of the foundation pit rises,the top of the foundation is observed.The foundation pit is displaced from the exterior by an unbroken wall,with a range of displacement values from small to large before diminishing.As the wall’s depth grows,the displacement of the wall body points towards the pit,and the displacement distribution is a "small at both extremities and large in the middle."",showing a bulging belly shape.(4)As the excavation depth of the foundation pit rises,the pressure disparity between its inner and outer sides gradually grows,leading to an augmented horizontal displacement of the soil towards the pit.The most significant displacement is situated on the long side of the foundation pit.The uplift value of the soil at the bottom of the pit is also increased.Also continuously increasing,and the maximum uplift position is located in the middle of the pit without columns.The foundation pit’s surface settlement is distributed in a groove fashion;as the distance from the pit’s edge grows,the settlement initially decreases,then rises,then diminishes,until eventually it reaches nothingness.(5)Analysis of the axial force and deformity of the foundation pit support structure under various schemes was conducted by varying the stiffness and structural makeup of the internal support components.It was found that as the support stiffness increased,the foundation pit support effect became better.(6)Compared with the support effect of the reinforced concrete inner support structure pit supporting scheme under the same support conditions,it is concluded that both support schemes can meet the pit supporting requirements.The prefabricated inner support scheme is more in line with the notion of green and sustainable development,yet it is slightly inferior to the latter.After the construction is completed,it can be recycled,disassembled and assembled more conveniently,and pollution-free.