Research On Torsional Dynamic Parameter Identification Of Nuclear Containment Vessel Under Earthquake

Nuclear containment vessel is the last security barrier to prevent nuclear leakage of nuclear reactor. To evaluate nuclear containment vessel correctly and effectively is related to its seismic torsional security. Nuclear containment vessel maintains normal operation of nuclear power plants and ensures personal security. Meantime, the complexity of torsional vibration characteristics and uncertainty of dynamic parameters to structural parameter identification technique and seismic damage monitoring work have brought new challenges. It is very important to identify torsional dynamic parameters of nuclear containment vessel under earthquake action, and applys it to seismic damage detection and safety assessment of anti earthquake torsion. The paper studys prestressed concrete containment of a nuclear power plant, based on state space method and unknown input structure physical parameters of time domain identification methods to identify dynamic parameters under earthquake, and to determine the most unfavorable position of nuclear containment vessel structural torsion. In this paper, the following work is carried out to study and obtains relevant results:(1)Dynamic time history of elastic torsional seismic response and control indexes of torsion effect on nuclear containment vessel are studied. Under the dead-weight or dead-weight and prestressed combination two kinds of working conditions analysing its elastic dynamic earthquake effect time history, and studing prestress stiffness on seismic behavior of nuclear containment structures. Based on torsional component ratio, torsional period ratio, storey drift angle,torsional displacement ratio,torsional effect coefficient index, analysising nuclear containment vessel that elastic torsion effects under earthquake action.(2)A new method is proposed to directly identify modal parameters of structure by using the least square method, and physical parameters of system can be estimated indirectly by modal parameters. Through establishment of continuous time and discrete time state space model, sampling points of continuous time of system are dispersed, and discrete time state space identification criterion is given, Gauss white noise is added, physical parameters of containment vessel are identified in the practical engineering, to further determine structural damage degree and the most unfavorable position, and time history of input ground motion is invertedSuccessfully.(3)A composite inversion algorithm based on combination of full amount compensation method and statistical average method is proposed. By using this idea, time domain identification of nuclear containment vessel structure with unknown input is constructed. Three kinds of identification of damping coefficient are introduced, which are mass proportional damping, stiffness proportional damping and Rayleigh damping. Comparison of recognition accuracy of structural layer damping in the state space identification method, it is demonstrated that this method greatly improves recognition accuracy of proportional damping parameters and corresponding layer torsional rigidity. Finally, it is proved that the proposed algorithm has a stronger ability to adapt to the noise in the identification of weak parts that structural torsion damage with a higher recognition accuracy and inversion of the input ground motion when processing has the best inversion results.