Prestress Loss Analysis And Prediction Of Nuclear Power Containment Structure

The importance of nuclear energy as a safe and clean energy source is extremely significant and has been valued and utilized worldwide.As an important peripheral protection structure,the safety of the containment is the primary issue of nuclear power plant maintenance and research work.At present,most of the containment structures are prestressed concrete containment structures.The long service life of nuclear power plant containment is influenced by the environment,loading and other factors,and the loss of prestress is a key factor affecting the performance of the containment structure.In this paper,a combination of theoretical calculation model and intelligent algorithm is used to optimize and predict the long-term loss of prestress caused by three factors: shrinkage of concrete,creep and relaxation of prestressing reinforcement,and finite element analysis software is used to study the effects of whether to consider the casting process,considering only creep deformation and considering the total loss of prestress on the mechanical properties of the containment respectively,and the limit value of the loss of prestress of the containment and The mechanical properties of the containment under the limit value were studied.The main contents are as follows:1.A method of parameter inversion and prediction based on the measured data of prestressing long-term loss is proposed.By analyzing the calculation equations given in the Specification for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG 3362-2018)and the ACI209-1992 specification,a sensitivity analysis is performed on the parameters of the two specifications for the phenomenon that the calculated values of prestressing long-term loss have large deviations from the measured values,and the parameters to be inverted are determined The inversion was carried out using a variety of swarm genetic algorithms,and the computational model was optimized using the inversion values of the parameters,and the long-term prestress loss values of the test beams were predicted.2.Based on the existing ACI209 and JTG 3362-2018 models,the age-adjusted effective modulus method was used to introduce the aging coefficient with time,and the effect of concrete aging with time on the modulus of elasticity and eventually on the creep was considered.In the ABAQUS finite element analysis software,an analytical model of the containment was established,and the design value of the elastic modulus of concrete was replaced by the effective modulus of the corresponding construction time to realize the simulation of the concrete creep effect in finite elements,and the change of mechanical properties of the containment considering only creep deformation was obtained.And the two working conditions without considering the concrete casting process and considering the concrete casting process are compared and simulated.3.A typical service life was selected,and the prestress values of each unit node of prestressing tendons were derived to form a calculation model considering total prestressing loss in the absence of other loads.The mechanical properties of the containment,such as the maximum main tensile stress of concrete,radial displacement of concrete,vertical displacement of dome,stress of prestressing tendons and maximum tensile strain of steel lining,were obtained during the 60-year service life of the containment.4.The mechanical response of the containment deformation and steel lining strain at 60 years of service of the concrete in the containment under the design reference internal pressure was studied.The initial value of prestress loss at 60 years of service was taken as the initial value,and the prestress loss was continuously increased until the containment structure exceeded its elastic limit state and functional failure state,which was expressed as tensile damage of concrete in finite element,and the limit value of prestress loss was obtained to analyze the mechanical response of main tensile stress and steel lining strain of containment concrete at this time,which provided a basis for the study on the life of containment.The analysis of the mechanical response of the concrete main tensile stress and steel liner strain at this time provides a basis for the study of the aging of the containment.