Experimental Study On Mechanical Performance Of Nuclear Power Containment Truncated Cone Region

With the rapid development of China’s nuclear power industry,the structural performance of nuclear power containment,as the last safety barrier of nuclear power plant,has attracted extensive attention.Studying the stress characteristics of containment structure and reasonably designing the reinforcement of the structure is an important means to prevent nuclear leakage and improve economy.The truncated cone area of nuclear power containment(the junction of shell and raft foundation)has irregular shape and complex stress,which is one of the weak links of containment structure.Studying the stress mechanism of this area is very important to master the structural performance of the whole containment.Therefore,taking the truncated cone area of nuclear power containment as the research object,this paper studies the mechanical characteristics of the truncated cone area by means of experimental research,numerical simulation and theoretical calculation.The main research contents are divided into the following parts:(1)ABAQUS software is used to calculate and analyze the sector containment model,and the size,load condition and boundary condition of the test piece model in the truncated cone area are designed with reference to the analysis results.Through the calculation and analysis of the specimen model in the truncated cone area,the effectiveness of the specimen model in the truncated cone area is verified by comparing the yield position and yield load of the reinforcement of the two models,the tensile damage degree of concrete when the reinforcement yields,and the plastic damage trend of concrete.Referring to the specimen model in the truncated cone area,the geometric dimensions,reinforcement mode,boundary conditions and load conditions of the test members are designed.The specimen loading device is designed for different load conditions to ensure the smooth loading of the test.Conduct material property test on the concrete and reinforcement used in the test piece in the truncated cone area to obtain the strength of concrete and reinforcement.(2)Load tests were carried out on the specimens in the truncated cone area under two load conditions.The test results show that the concrete cracks of specimen 1(condition 1)mainly appear in the middle of the inner bottom plate and the junction between the inner bottom plate and the truncated cone,and the maximum crack width is 6mm;The failure mode of specimen 1 is bending shear failure,and the yield position of reinforcement mainly appears in lines H1 ～ H4;The maximum horizontal displacement of the structure is27.7mm and the maximum vertical displacement is 6.8mm.The concrete cracks of specimen 2(condition 2)mainly appear at the junction of the inner bottom plate and the truncated cone,and extend along the inner bottom plate to the enlarged end,and the maximum crack width is 35mm;The failure mode of specimen 2 is shear failure,and the yield position of reinforcement mainly appears in rows H1 ～ H4 and column S1;The maximum horizontal displacement of the structure is 32.6mm and the maximum vertical displacement is49 mm.(3)ABAQUS software is used to simulate the specimens in the truncated cone area under different load conditions.The effectiveness of the finite element model is verified by comparing the failure mode,reinforcement stress-strain and load displacement curve between the finite element model and the test specimen.It is found that for the specimens in the truncated cone area under two load cases,the failure mode of the finite element model and the stress-strain of the reinforcement are basically consistent with the test results.The load displacement curves of the two are in good agreement in the early stage of loading,but there are great differences in the later stage of loading.(4)Using the topological optimization function of ABAQUS software,a simplified strut-and-tie model in the truncated cone area is established.It is found that the simplified strut-and-tie model can reflect the stress characteristics of the truncated cone area.Referring to the strut-and-tie model of corbel and prestressed anchorage zone,combined with the stress trace diagram of truncated cone area,a refined strut-and-tie model of truncated cone area is established.The refined strut-and-tie model in the truncated cone area is imported into grasshopper software.The SAP2000 software is called through grasshopper software,and the most reasonable strut-and-tie model is continuously optimized by genetic algorithm.According to the strut-andtie model,the reinforcement design of the truncated cone area is carried out.The results show that the truncated cone area needs to focus on the horizontal reinforcement in H1 ～ H3 rows,the vertical reinforcement in S1 column,the stirrup of the inner bottom plate and the stirrup of the outer bottom plate.According to the reinforcement results of the strut-and-tie model,a new finite element model is established for simulation,and the simulation results are compared with the results of the original model 2.The results show that the refined strut-and-tie model in the truncated cone area is effective.