In-plane Shear Analysis Of Reinforced Concrete Walls Based On Modified Compression Field Theory

“Hualong one”(HPR1000)is the Genneration 3 PWR nuclear power plant with independent intellectual property rights in China,and the high-temperature gas-cooled reactor(HTR)is the Genneration IV nuclear power plant still in development.The design peak acceleration of ground motion for HPR1000 is 0.3g,so that significant horizontal earthquake action is applied to the prestressed concrete containment,and the in-plane shear is important as part of the design.Reinforced concrete walls in the Genneration IV HTR nuclear power plant reactor buildings belong to the low-rise shear wall mainly subjected to shear force.The design calculation formulas adopted by the relevant design specifications in China and the United States,for nuclear power plant prestressed concrete containment and reinforced concrete walls,are very simple,which then results in overcrowded shear reinforcement in the concrete wall.Meanwhile,the numerical simulation for shear behavior of low-rise reinforced concrete walls has always been a difficult point in research.Thus,in this paper,the shear behavior of prestressed concrete containment and reinforced concrete walls in nuclear power plants is studied.The accuracy of five different in-plane shear analysis models is analyzed based on experimental results of the 1:3 scale specimens of reinforced concrete walls in the South Korean APR1400 nuclear power plant.Analysis models are rotating angle softened truss model,fixed angle softened truss model,softened membrane model,modified compression field theory model with crack check,and modified compression field theory model without crack check but with a replaced concrete tensile constitutive equation the same as rotating angle softened truss model.It's shown that the modified compression field theory model without crack check but with a replaced concrete tensile constitutive equation the same as rotating angle softened truss model is the best one.Using the modified compression field theory model without crack check but with a replaced concrete tensile constitutive equation the same as rotating angle softened truss model,and considering the tensile strength of concrete,the mechanism of reinforced concrete elements subjected to shear is analyzed.The evolution of stress in concrete and reinforcing bars in elements from the beginning of loading to the yield of reinforcing bars in two directions is studied,then the compressive and tensile effects of concrete in elements are clarified.It's shown that after concrete crack in the element,the truss bearing mechanism with concrete as the strut and the rebar in two directions as the ties will be formed,and that the tensile strength of concrete has little contribution to the shear capacity of the elements.In view of the problems of overcrowded in-plane shear reinforcement according to the calculation formula of Design requirements for nuclear safety related concrete structure for pressure water reactor nuclear power plant(NB/T 20012-2010)in engineering,the shear bearing mechanism of reinforced concrete elements are analyzed,and two methods for the reinforcement calculation based on the element static equilibrium and the optimization analysis are proposed taking the wall as a whole.It's shown that 6~7% of the amount of reinforcement can be saved when the in-plane shear reinforcement of the reinforced concrete walls is designed according to the proposed method in this paper.Finite element program based on modified compression field theory is developed using MATLAB and connected with ANSYS pre-and post-processor,then the numerical simulation for the low-rise shear walls test of high-temperature gas-cooled reactor nuclear power plant is performed,and the simulation results are in good agreement with the experimental results.