变刚度刚性桩复合地基在地震作用下的性状分析

发布时间：2018-05-25 03:24

本文选题：刚性桩复合地基 + 变刚度调平　；参考：《太原理工大学》2015年硕士论文

【摘要】：高层建筑中地基基础的设计是比较复杂的问题，特别是在土质较差的地区，随着建筑高度的增大，上部荷载逐渐增加，会引起地基基础的不均匀沉降，使得基础和上部结构产生较大的内力，这对于基础的合理设计提出很大的挑战。针对以上问题，设计师提出变刚度刚性桩复合地基调平的概念，通过调整地基或者桩基的竖向支承刚度分布，促使差异沉降减到最小，基础或者承台内力和上部结构次应力显著降低。同时使地基基础达到承载力和抗震要求、降低工程造价的综合效果，目前已在实际工程中逐渐推广。本文采用土体-上部结构动力相互作用的方法，基于ABAQUS有限元分析软件，对变刚度刚性桩复合地基-基础筏板-上部结构进行整体有限元动力时程分析，，分析总结变刚度刚性桩复合地基抗震性能和上部结构地震动力响应的变化规律，具体内容包括以下几方面：（1）文章对刚性桩复合地基动力分析的方法进行探讨，基于ABAQUS对复合地基-筏板基础-上部结构整体有限元模型进行建立，并对建模过程中桩-土-上部结构动力相互作用的关键性问题进行探讨。（2）通过采用分块Lanczos法对整体模型进行地震模态计算，得出：随着复合地基筏板两侧竖向支承刚度的减小，体系对应的阵型固有频率减小，固有周期增大。（3）对变刚度刚性桩复合地基的调平原理进行初步分析，在自重荷载作用下，基础筏板沉降呈现碟形分布特性，表现为中心沉降较大，边缘沉降较小的特点；经过变刚度调平设计优化，对筏板基础能够进行有效的调平，减小差异沉降，降低内力。（4）采用时程分析法对刚性桩复合地基变刚度调平前后桩体的地震动力响应进行分析。变刚度调平前，边桩的最大弯矩、最大轴力和相对水平位移均大于中间桩；变刚度调平后，长桩的弯矩和水平位移远大于短桩，长桩弯矩有多个峰值，最大弯矩发生在复合地基变刚度处，故要加强边桩和桩身变刚度处的强度设计。（5）采用时程分析法对刚性桩复合地基变刚度调平前后基础和上部结构的地震动力响应进行分析。在地震水平力作用下，调平前后筏板基础的差异沉降和内力均增大，二次差异沉降和基础内力随着筏板两侧竖向支承刚度的减小而增大；上部结构的地震动力响应随着筏板两侧竖向支承刚度的减小而增大。同时总结了变刚度刚性桩复合地基抗震性能的优劣，并对实际工程提出一些有价值的具体建议。
[Abstract]:The design of foundation is a complicated problem in high-rise building, especially in the area of poor soil quality, with the increase of building height, the upper load increases gradually, which will cause the uneven settlement of foundation. It makes the foundation and superstructure produce larger internal force, which poses a great challenge to the reasonable design of foundation. In view of the above problems, designers put forward the concept of variable stiffness rigid pile composite ground tone level. By adjusting the vertical support stiffness distribution of foundation or pile foundation, the differential settlement is reduced to the minimum. The internal force of foundation or cap and the secondary stress of superstructure are significantly reduced. At the same time, the foundation can meet the requirements of bearing capacity and seismic resistance, and reduce the comprehensive effect of engineering cost, which has been gradually popularized in practical engineering. In this paper, the method of soil-superstructure dynamic interaction is used to analyze the dynamic history of variable stiffness rigid pile composite foundation, raft and superstructure based on ABAQUS finite element analysis software. This paper analyzes and summarizes the variation law of seismic behavior and superstructure dynamic response of variable stiffness rigid pile composite foundation, including the following aspects: In this paper, the dynamic analysis method of rigid pile composite foundation is discussed, and the integral finite element model of composite foundation, raft foundation and superstructure is established based on ABAQUS. The key problem of pile-soil-superstructure dynamic interaction in modeling process is discussed. 2) by using block Lanczos method to calculate the seismic modes of the whole model, it is concluded that with the decrease of vertical support stiffness on both sides of the raft, the corresponding natural frequency of the system decreases and the natural period increases. 3) the leveling principle of variable stiffness rigid pile composite foundation is preliminarily analyzed. Under the action of deadweight load, the settlement of foundation raft presents the characteristics of dish shape distribution, which shows that the center settlement is large and the edge settlement is small. Through the optimization of variable stiffness leveling design, the raft foundation can be effectively leveled, the differential settlement can be reduced, and the internal force can be reduced. 4) the seismic dynamic response of pile body before and after variable stiffness leveling of rigid pile composite foundation is analyzed by time history analysis method. Before leveling with variable stiffness, the maximum moment, maximum axial force and relative horizontal displacement of the side pile are greater than those of the intermediate pile, and the bending moment and horizontal displacement of the long pile are much larger than those of the short pile after the variable stiffness leveling, and the bending moment of the long pile has multiple peaks. The maximum bending moment occurs at the variable stiffness of composite foundation, so the strength design of side pile and pile body should be strengthened. 5) the seismic dynamic responses of foundation and superstructure before and after leveling the variable stiffness of rigid pile composite foundation are analyzed by time-history analysis method. Under the action of seismic horizontal force, the differential settlement and internal force of raft foundation increase before and after leveling, and the secondary differential settlement and foundation internal force increase with the decrease of vertical support stiffness on both sides of raft. The seismic dynamic response of superstructure increases with the decrease of vertical support stiffness on both sides of raft. At the same time, the merits and demerits of the composite foundation with variable stiffness and rigid pile are summarized, and some valuable suggestions for practical engineering are put forward.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU470;TU435

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