Research On The Selection And Structural Design Of Prefabircated Multi-layer Underground Garage

In recent years,with the rapid increase of vehicle ownership in China,the solution of parking problems and the promotion of parking lots are attracting more and more attention from entire society.Under the complex and crowded urban environment,the prefabricated underground garage is becoming a new solution for urban parking lot because of its high space utilization,small area and fast construction efficiency.In this paper,the key problems in the planning and design of the new type prefabricated underground garage and the new special structure of the garage are studied with the intelligent underground garage test project in Chongqing,which can provide a reference for the construction of prefabricated underground garage.The main works and achievements of this paper are as follows:(1).The influence factors of the underground garage type selection are summarized and analyzed detailed,and ten essential factors are extracted respectively from environmental benefit,economic benefit and social benefit.Based on the optimized AHP principle,a evaluation model which has four layers and thirteen elements is established for garage selection.According to the actual engineering data and the result of expert investigation,the selection analysis and judgement matrix calculation of the underground garage are carried out,and the evaluation of the selection of the type of underground garage is quantified.Under the premise of guaranteeing the conformance,it is found that the laneway-stacker-type underground garage of cross roadway is the best result to meet the actual engineering needs.(2).On the basis of the laneway-stacker-type underground garage,the garage prefabricate system is summed up in combination with the practical engineering and the existing experimental research experience.the special garage is divided as a prefabricated construction and its mechanical properties of two different joints and partitioning modes are compared with the cast-in-suit structure.The position of the bottom plate connector and the side wall joint is respectively moved.The internal force change rules of the two locations are summarized and analyzed,and the most reasonable structural division method is obtained.With moving the position of the bottom plate joint and the side wall joint,the internal force change rules of the two locations are summarized and analyzed to obtain the most reasonable structural prefabrication method.Two kinds of prefabrication type underground garage under the condition of different joint stiffness is analyzed.It is found that the influence of the stiffness change is quite different in these two kinds of structure.The change of the stiffness of the joint leads to the redistribution of the internal force of the structure.The reduction of the stiffness will easily make the state of the component tend to be articulated at both ends,and the positive moment region increases with the increase of maximum value.(3).The three-dimensional model of the assembled underground tunnel stacker garage is established according to the actual project.The nonlinear transient time history analysis is carried out under the consideration of the contact response of the joint.The key seismic problems of the assembled solid garage structure are studied.The dynamic and deformation characteristics of the laneway-stacker-type underground garage structure under the action of the actual seismic wave level,vertical and two-way coupling of seismic fortification intensity are compared and summarized.The difference between the two prefabricated structures and the cast-in-suit garage's seismic deformation performance is quantitatively contrasted by the interlayer displacement angle.The vertical seismic performance of the cast-in-suit structure and the prefabricated structure is analyzed through the roof deformation,and the overall performance of the two different assembly structures is reasonably evaluated.(4)Combined with the study of the assembly type garage division system and the analysis results of the seismic performance in two different prefabrication structures,and considering the factors such as structural waterproof,construction difficulty and assembly rate,the design of the stacked garage for the assembled underground tunnel is synthetically evaluated,which can provide reference and guidance for the construction of the follow-up engineering.