Bending Capacity Of Reinforced Concrete Members With Annular Sections And Sectional Analysis

Driven by the increasing demand of wind turbine towards large capacity of single machine,prestressed concrete-steel hybrid wind turbine tower has become a very competitive structural type.The main function of concrete tower in hybrid tower is to ensure the overall strength,stability and seismic performance of the structure.At present,there is no relevant code or standard specifically for the concrete structure of wind turbine towers both in China and abroad.Chinese design engineers mainly refer to Code for Design of High-rising Structures(GB50135)and Code for Design of Chimney(GB50051)to calculate the structural strength of the tower.But there are the following problems: First,the current formula for bending bearing capacity of reinforced concrete with annular sections is obtained from the research on normal strength concrete and original grade ?,?,and ? steel bars,and there is no clear conclusion about the suitability of the formula for high-strength materials members.Secondly,the load characteristics of the wind turbine tower and the chimney are quite different,and the structural numerical analysis model needs to be determined.In response to the above problems,the corresponding numerical analysis research was carried out,the main research work is as follows:(1)On the basis of previous studies,the thesis introduces the calculation method of bearing capacity of the annular section of normal strength concrete,and discusses the applicability of the calculation formula of the annular section members to the high-strength reinforcement(HRB400,HRB500)in the current structural design code.(2)Based on the principle of layered method,the nonlinear analysis program of the whole process of moment-curvature of annular section members was compiled by MATLAB.Different material constitutive models are selected to carry out numerical analysis of non-prestressed and prestressed annular section members,and the calculation results are compared with the test results to explore the rationality of the calculation model.The main conclusions of this thesis are as follows:(1)When the code formula is applied to high-strength material members,there is an unsafe error.In this thesis,the approximate relationship of relevant parameters in the code formula is modified,and the improved bearing capacity calculation formula is safer for the section design.(2)For the non-prestressed annular section members with large thickness,the confinement of concrete provided by stirrups needs to be considered in the concrete calculation model.Mander concrete model selected in the analysis is ideal for predicting the ultimate bearing capacity and ultimate curvature of members.For the prestressed annular section members with relatively small thickness,compression softening of concrete needs to be considered in the concrete calculation model(3)The longitudinal steel in the compression zone of the prestressed concrete tower is prone to buckling under the action of prestress and external loads.The simulation results considering the softening effect of concrete and the buckling of compressive steel bars are in good agreement with the experimental results.From an engineering perspective,the area of prestressed reinforcement can be appropriately reduced,and the mechanical properties of the materials can be fully utilized under the premise of ensuring structural safety and economy.