地基—桩（筏）—上部结构动力相互作用分析

在建筑结构的抗震工程设计中通常假定地基为刚性的。对于建立在基岩和坚实场地土上的结构,这种刚性地基假定是合理的。然而,大量的理论分析和研究表明,在地基土质较差的情况下,地基—基础—上部结构动力相互作用对结构物的动力特性具有十分重要的影响,其地震响应将发生显著的变化。广大研究者和工程技术人员在实践中已经意识到将上部结构和基础考虑作为一相互作用的整体进行设计的必要性和优越性,无论是对于静力还是动力特性研究,群桩—土—结构作为一个整体计算出的结果不仅与通常的刚性地基假定所得有较大出入,而且不同土层土质、群桩属性条件下的相互作用体系所表现的受力与变形特点也不尽相同。本文试图通过理论分析和试验研究,认识地基—基础—上部结构动力相互作用机理,为实践应用提供适合工程设计、比较简捷的实用计算方法,为考虑地基—桩(筏)—上部结构动力相互作用的抗震设计提供一定的理论依据和设计建议。本文共分为五章,分别做了如下工作: 1、通过对大量相关文献的阅读总结,分析了国内外开展土—结构动力相互作用研究的现状及发展水平,并特别对地基—桩—上部结构动力相互作用的方法进行了归纳,评述了已有研究工作成果的局限性及优缺点,提出了本文针对桩基上下部结构体系所采用的理论分析途径和基本框架思路; 2、本论文采用Novak薄层法,分析了单桩的竖向、扭转、水平及水平-摇摆耦合振动。然后,引进Novak和韩英才的边界层理论,全面分析和对比了匀质弹性、匀质粘弹性和非匀质粘弹性地基中单桩的动力阻抗,在分析中,本文首次将边界层理论推广到求取地基水平动力阻抗,扩展了这种简化方法的使用范围,考察了各种因素对单桩动力阻抗的影响程度。在推导单桩水平动力阻抗的过程中,采用克雷洛夫函数和初参数法求解单桩的水平振动微分方程,从而能够方便地考虑桩长和桩底土对单桩动力阻抗的影响。计算表明,当桩的长径比较小时,桩底土对单桩动力阻抗有重要的影响。而且本文首次将Novak薄层法引伸至求取Rayleigh波、SH波作用下的粘弹性地基、层状地基、径向非匀质层状地基中的单桩水平和竖向动力位移响应,并就泊松比、长径比、桩土刚度比、阻尼比等参数对单桩动力位移响应沿桩长方向分布的影响做了详细的分析,分析表明,不同的桩底支撑条件下,各因素所起的作用有很大差距。 3、采用动力相互作用因子和位移法,全面推导了刚性承台群桩在匀质弹性地基、匀质粘弹性地基及非匀质粘弹性地基中的竖向动力阻抗、摇摆动力阻抗、水
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The current version does not support copying Cyrillic text to the Clipboard. You should activate the programsolve the differential equation of single pile horizontal vibration. Hence it is convenient to consider the influence upon impedance produced by pile length and the soil under piles. The calculation examples demonstrate that the soil under piles will greatly influence the impedance of single piles.3.Dynamic interaction factor and displacement method are adopted to derive vertical, torsional, rocking, horizontal and coupled horizontal-rocking vibrations of pile groups under rigid bearing-cap in homogeneous elastic soil, homogeneous viscoelastic soil and inhomogeneous viscoelastic soil. Displacement method is more explicit in conception, more simplified in derivation and less sophisticated in calculation than force method. In terms of Gazetas’s three step procedure for pile-soil-pile interaction in homogenous media a new method for calculating dynamic interaction factors of layered-soil is suggested under harmonic, Rayleigh wave and SH wave excitation and the simplified scheme applied to interaction of pile-groups and soil is further extended.4.It is the most difficult for analysis of dynamic soil-structure interaction that the test data is poor. So the theoretical analysis of dynamic soil-structure interaction is accepted and its application is limited. But in this paper a 1:2 model test of dynamic soil-pile-frame structure interaction is researched. As known, the test is the biggest one of interrelated tests. Under harmonic and impulsive excitation at top of the model, lots of test data are got. These data will be benefit to identify the dynamic interaction mechanism of soil-foundation-superstructure and approve the theory of dynamic soil-pile-superstructure.5.A simplified formula that can be used widely is developed to calculate fundamental period of interaction systems. The comparison between test data demonstrates its precision.