空间耦合基础提离模型的开发与应用

The basemat uplift phenomenon of buildings with large aspect ratio will be generated during strong ground motion.The storey drift and the internal force of the component varies during the procedure of uplifting. Therefore, in order to predict the response of the buildings with larger aspect ration accurately, it is nessary to study the theoretical mechanism of the uplift phenomenon of the foundation.During the past few decades, due to the investigation of the earthquake demage, it was observed that the demage of low-rise concrete buildings were lower than the design expect.Some of the investigated low-rise concrete buildings have a same characteristic that the foundation of the building uplifted during the strong ground motion. Therefore,lots of researchers become pay attention to the uplift phenomenon of the foundation. However, until now, the proposed uplift model of the foundation have some limitations, lots of the proposed uplift model just focus on the change of the response of the super structure in the direction where the uplift phenomenon happens, the change of the response of the orthogonal direction is ignored.As we know, if the uplift phenomenon generates in the horizontal x direction, not only the impedance of the foundation in X direction changes, the impedacne of the foundation in Y direction will aslo changes due to the reduction of the conection area between the foundation and the soil around it. Thus, a new uplift model which can consider the coupling effect of three dimension space is urgent needed. In this project, a new uplift model which can consider the above mentioned coupling phenomenon is proposed, with this proposed uplift model, the varies of the impedance of the foundation due to the uplift phenomenon can be estimated in three-dimensional directions at the same time during the seismic excitation. The proposed uplift model will provide the theoretical support to the analysis of the response of the structure considering the uplift phenomenon. The proposed model can also predict the response of the structure when the uplift phenomenon of the foundation generated in the two horizontal directions(x,y) at the same time.

高宽比较大的中低层结构在强地震作用下易产生基础提离等几何非线性现象。基础发生提离时，上部结构的层间位移及构件所承担的弯矩、剪力将发生相应的变化，因此针对基础发生提离几何非线性现象的研究，有利于精确预测高宽比较大的中低层结构在强地震作用下的动力响应，为建筑物的预警保护及结构设计提供一定的理论依据。既往研究仅关注当基础发生提离时沿基础提离方向的上部结构动力响应的变化，而未考虑基础在水平一个方向（例如x方向）发生提离时，对未发生提离方向（例如y方向）结构体系动力响应耦合效应的影响。本项目提出一种空间耦合基础提离模型，预测空间各个方向地基阻抗随基础提离量的变化，为全面分析上部结构动力响应随着基础提离而产生的变化提供理论支持。由于提出的基础提离模型具有空间特性，因此可以分析基础在水平双向同时发生提离时结构体系的动力响应。

高宽比较大的中低层结构在强地震作用下易产生基础提离等几何非线性现象。基础发生提离时，上部结构的层间位移及构件所承担的弯矩、剪力将发生相应的变化，因此本项目针对基础发生提离几何非线性现象进行研究，提出了可以同时考虑空间六个自由度的空间耦合基础提离模型。本项目提出一种空间耦合基础提离模型，预测空间各个方向地基阻抗随基础提离量的变化，为全面分析上部结构动力响应随着基础提离而产生的变化提供理论支持。同时采用薄层要素法验证了所提出的空间耦合基础提离模型的正确性。借助本项目所提出的空间耦合基础提离模型。推导了考虑基础提离情况下上部结构-基础体系的运动方程，并编写了相应的计算程序。通过对一个水塔结构进行分析，系统研究了考虑基础提离情况下水塔上部结构及基础动力响应的变化，同时研究了水塔结构基础提离时其地基阻抗的变化情况。