为考虑土-结构相互作用对输入地震波的影响，基于两步法思想，建立了考虑辐射阻尼效应的等效输入地震波。在该种方法中，将单自由度体系的基础地震反应为上部结构的输入，然后用状态空间法计算考虑土-结构相互作用后体系阻尼比的变换情况，用以修正上部结构的阻尼系数，从而利用刚性基础的反应近似计算土-结构相互作用的影响。对一个单自由度体系和一个5层框架结构进行计算分析，算例分析表明，直接利用自由场的地震波或基岩波作为上部结构的输入，计算误差甚至超过100%，而两步法可使体系的计算误差小于10%，采用修正阻尼系数的两步法，误差将小于5%，满足工程需要。

Taking account of soil-structure interaction on seismic wave input, based on the theory of a two-step method, equivalent seismic wave input considering radiation damping effects is established. Firstly, the base response of single degree of freedom system is considered as the input of superstructure; and then damping ratio of the system is calculated by the state-space method considering soil-structure interaction, which is used to modify the damping coefficients of superstructure; thus the impact of soil-structure interaction is approximately calculated from the response of rigid foundation. Subsequently, a single degree of freedom system and a five-story frame structure are analyzed; numerical examples show that the calculation errors even exceed 100%; while directly taking seismic wave of free field and bedrock as the input of superstructure. However, the calculation errors of the two-step method are less than 10%; furthermore, the calculation errors will be less than 5% adopting the modified damping two-step method, which can satisfy the requirements of engineering.