核电结构抗震设计中高阶振型组合方法探讨

Discussion on high frequency modes combination methods in nuclear stucture seismic design

本文探讨核电工程中结构在含有高频分量的地震波和反应谱输入条件下的反应特性。在高频分量丰富的输入条件下,因为模态间反应同相及准静力问题,刚性结构即使模态取得很高也容易产生有效质量达不到规范要求的情况,即残余刚性反应的拟静力特性导致质量丢失问题,一般的模态组合方法此时不再适用,计算结果将偏于不安全。此时需要将结构的刚性反应和周期性反应剥离开来分别计算。论文对NRC认可的分离非同相和同相反应的计算方法进行了理论介绍,并结合某工程的一个支撑结构实例进行了考虑刚性反应的模态组合计算,通过比较支座反力阐述了计算方法导致的差异。论文工作将有助于对核工程领域刚性结构抗震设计和计算方法更好的了解和应用,提出的方法对民用工程结构抗震中也具有借鉴意义。

Response characteristics of nuclear engineering structures with high frequency components in seismic input motion are investigated and discussed. For rigid structure with such seismic input, because of in-phase and pseudo-static effect, the structures are more likely to meet the problem that effective participation mass can not satisfy the demand of design code. Namely, the pseudo-static behavior caused by residual rigid response will lead to a limited application for common combination method,And the calculation results tend to be unsafe.In such situation, the rigid responses need to be separated from the periodic ones and evaluated individually. Method seprating in-phase responses from out-of-phase responses recognized by NRC is introduced theoretically. Furthermore, a support structure example calculation in one nuclear project is carried out, and modes combination method takes separating rigid response into account. The difference caused by calculation methods can be observed by checking the results of structure supporting forces. The studies are helpful to a better understanding and application for design and analysis of nuclear engineering strctures when considering high frequensy problems. The combination method introduced herein can also provide support for other civil engineering seismic design.