城市密集建筑群在强震作用下因相邻结构碰撞和结构—土—结构相互作用等动力群效应现象导致建筑物破坏严重，限于目前土—建筑群动力耦合系统建模困难和地震响应计算代价高等问题，动力群效应作用机制和密集建筑群震害规律尚待阐明。本项目针对城市密集群体建筑与场地土体组成的动力耦合系统，首先提出土—建筑群系统集总参数模型建模方法，其中重点研究土—群体基础耦合动力阻抗函数、系统非线性滞回模型及模型参数标定方法，以实现大尺度场地、大规模建筑群系统的简化建模；其次针对结构—土—结构动力相互作用的时滞性、结构倒塌和碰撞的强非线性、动力群效应的局部影响性等特点，提出土—建筑群动力耦合运动方程的变步长时程积分算法和解耦机制，进而建立具有动态适应能力的高效时程分析算法；在此基础上，开展典型区域建筑群地震响应参数分析，揭示动力群效应特征和密集建筑群震害规律，开发城市建筑群震害模拟系统，为城市震害预测和损失评估提供科学依据。

Dense urban buildings are prone to the dynamic group effect including seismic pounding and the though-soil interaction between adjacent buildings when subjected to strong earthquakes, leading to severe damage to the buildings. Due to modeling difficulties and high computation costs of soil-building group interaction analysis, the dynamic group effect mechanism and its influence on the seismic damage to building groups still wait to be clarified. First, a lumped-parameter model for simulating dynamic soil-building group interaction is proposed, which is focused on the derivation of dynamic impedance function of a group of foundations, nonlinear hysteretic models, and the associated modeling parameters, in order to facilitate modeling of a large-scale soil-building group interaction system. Then an efficient and adaptive solution algorithm is established to solve the equations of motion (EOM) of the seismic response of soil-building group interaction, with proposed variable-step numerical integration scheme and EOM decoupling scheme, considering the time-lags of mutual influence of adjacent buildings through the soil, the hard nonlinearities due to structural collapse and impacting, and the local dynamic group effect. Finally, parametric seismic response analyses of regional urban buildings will be carried out to obtain the characteristics of the dynamic group effect and its resultant damage to dense buildings, and an urban seismic damage simulation system will be developed to provide a scientific basis for urban seismic damage prediction and loss assessment.