为探讨同时考虑P-Δ 和P-δ 效应对单质点体系动力响应的影响，从“刚度折减”的角度进行了理论研究和数值计算．文中推导了精确考虑二阶效应的结构侧移刚度折减系数计算公式，指出二阶效应对结构动力响应的影响可以视为结构侧移刚度的折减; 提出了精确考虑单质点体系二阶效应的反应谱法的理论公式，并依据抗震设计规范标准反应谱进行了简化; 分析了静力和动力情况下，精确考虑二阶效应和只考虑P-Δ 效应的区别;还根据有限元数值计算结果对精确考虑二阶效应影响的理论公式进行了验证，结果表明理论公式与数值结果吻合较好．

In order to reveal the influence of dynamicand P －Δ and P －δ effects on the single-degree-of-freedom system ( SDOFS) ,the theoretical simulation and the numerical calculation are both conducted from the viewpoint of "stiffness reduction”. First,the formulae of the coefficient of the lateral stiffness reduction precisely considering second-order effects are deduced,which regard the influence of the second-order effects on the structural dynamic
response as the lateral stiffness reduction. Next,the theoretical formula of the response spectrum method precisely considering the second-order effects of SDOFS is proposed and is simplified based on the standard response spectrum of the seismic design code. Then,the differences between the P －Δ and P －δ effects and the P －Δ effect are examined under the static and the dynamic conditions. Finally,the proposed method is verified by the results of the finite element numerical calculation,finding that the results of the proposed method accord well with the numerical ones.