Research On Design Methods Of The Large Prestressed Concrete Tank Without Joints

With the rapid development of national economy,the growing scale of urban construction,land supply is becoming increasingly tense,resulting in the construction of underground garage is growing day by day.The status quo is:the design of underground garage garage single area is increasing,especially the length of the garage continues to expand,more and more of the plane size of basement,some even reach or exceed 200～300 meters,the design of super long garage will face a lot of problems.At present,the structure design of large garage when the main consideration is the normal use of conditions,the lack of attention to the construction conditions.Designers often think that the roof is covered with soil,the seasonal temperature difference is very small,as has been set by the specification requirements of the temperature after the cast strip is no need to calculate the temperature stress.But the reality is that construction is often the basement roof as the construction site,or that the design of pouring belt has been considering the temperature stress,the construction failed to cover soil,which led to the basement roof and exterior wall of large area cracking,moreover,encountered strong rainfall,leading to ventricular local resistance damage.Therefore,the design documents to cope with the construction of the soil and the underground water level control during the construction of a clear request,so that the situation and design results in line with the scene.Although the application of plate type raft foundation in pure basement engineering has been very extensive,but in engineering design there is a pier size too large,raft thickness is too thick,the actual coefficient of subgrade and foundation conditions,select the raft stress condition,especially the partial reinforcement pier such design is not reasonable,not economic phenomenon.Based on the above situation,this paper makes a detailed analysis of the main factors affecting the internal force of the plate raft foundation by calculating examples,in order to find out the variation law.This paper focuses on four key technical problems including:(1)the roof of large underground chamber temperature stress and crack distribution;(2)the basement wall stress,temperature stress and crack distribution;(3)the reasonable selection of plate type raft thickness and substrate pier;(4)no room under soil cover,according to the local anti floating problem of truss model and finite element analysis of underground chamber.The main results of this paper are as follows:1.In this paper,the composition of the indirect effect of the super long concrete structure and its calculation method are discussed,and the indirect action and the load action of the concrete structure are compared.In the design of super long concrete structure,it is a practical and effective method to reduce the shrinkage of concrete to the temperature difference,and to consider the creep effect as the elastic solution of the structure to be multiplied by 0.3.2.The need to consider the influence of concrete cracking stress of overlong concrete structure under the indirect effect analysis,discusses the internal force analysis of super long concrete structure in the indirect effect,and the roof,wall of a Nantong resettlement housing residential projects in the basement of the indirect internal forces are analyzed.The external wall of the basement roof on site constraints of overlong basement floor surrounding,out of plane stiffness influence on temperature stress can not be ignored,need to consider two kinds of cooling and heating conditions,and on the floor were considering and not considering the out of plane stiffness analysis of two kinds of assumptions.3.The design of super long concrete structure,not only to consider the use of load conditions,should also be appropriate to consider the adverse circumstances that may arise in the construction conditions such as large temperature caused by delay in soil stress,even basement anti floating accident.Shear reinforcement by construction conditions control bending,side span beam end bending reinforcement and the side span column,the design of related parts strengthened.4.In the precondition of achieving the same carrying capacity by using the finite element software analysis,to determine the different parameters(coefficient of subgrade,thickness,pier raft thickness,pier plane size etc.)influence on the mechanical properties of pure basement raft foundation under the.Under the premise of meeting the requirement of anti permeability and anti float,the thickness of the base plate is optimized,and the bottom plate reinforcement is adopted to reduce the crack of the bottom plate.5.The overall analysis than the equivalent frame to simplify the calculation of internal force has obvious advantages in the equivalent frame in the calculation process,the load transfer and the stiffness of the structure is often used to simplify measures,such as calculation of a frame,the span also requires the average error is simplified,the direction of two very large.6.From the reinforced concrete column crack location and morphology,the fracture characteristics and failure modes of the large enough under horizontal load,crack characteristics and failure form of frame beam in frame structure is very similar to the reason:if the floor,underground garage roof as "columns",the underground garage as frame column because of the"beam",column "section and stiffness," beam "section and weak stiffness,the horizontal load under the action of" inevitable "frame" is the actual underground garage column first cracking,and in large enough "horizontal load",the damage is very serious.