【作者】 孔德森；

【导师】 栾茂田；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2004， 博士

【摘要】 作为一种强度高、承载力大、耐久性好的重要深基础形式,桩基础在高层建筑、大型厂房、水利水电枢纽、铁路工程、公路工程、桥梁工程、近海采油平台、核电站等土木、水利工程中得到了广泛应用。但由于桩—土—结构动力相互作用的机理与工作性能极其复杂,目前仍有很多问题没有得到彻底解决。为此,本文紧密围绕桩—土—结构动力相互作用特性研究中存在的主要问题,在单桩的动力阻抗计算方法与简化模型以及单桩、群桩和上部结构的动力响应分析等方面进行了系统而深入的研究。论文的主要研究内容及所取得的研究成果具体包括以下几个方面。 1.当运用子结构方法分析桩—土—结构体系的动力相互作用特性时,桩基动力阻抗的合理确定是一个关键的问题。本文运用土动力学和结构动力学原理,基于改进的Winkler地基梁模型,同时综合考虑桩周土的弱化效应、地基土的成层非均质性以及水平荷载作用时桩—土界面的相对分离效应和竖向荷载作用时桩—土界面的相对滑移效应,建立了水平荷载和竖向荷载作用下单桩动力阻抗的简化计算力学模型与分析方法,并进行了算例分析,将所得到的计算结果与有限元方法的分析结果及试验结果进行了对比分析,验证了建议分析方法的合理性,进而通过变动参数对比计算与分析,探讨了桩周土域弱化范围与弱化程度、桩—土界面接触状态、桩体长细比和桩—土刚度比等对单桩水平和竖向动力阻抗的影响规律。 2.单桩的动力响应特性研究是桩—土—结构相互作用分析中的一个重要而基本的内容。本文将桩视为置于Winkler模型地基中的梁,运用土动力学和结构动力学原理,分别对土和桩建立了波动方程与振动微分方程,并利用分离变量法进行求解,建立了能同时考虑桩周土在振动过程中的弱化效应和地基土的成层非均质性的单桩简谐动力响应分析的简化解析方法;通过与有限元计算结果的对比分析,验证了本文简化解析方法的合理性;进而通过变动参数比较分析,探讨了桩周土域弱化范围与弱化程度、地基土层条件、桩体长细比和桩—土刚度比等对单桩水平和竖向简谐动力响应特性的一般影响规律。 3.群桩是实际工程中普遍采用的桩基形式,由于要考虑桩—土—桩的相互作用效应,因此,群桩的动力响应特性远比单桩的复杂。本文根据动力相互作用系数的基本定义和求解步骤,引入某些假定,分别计算了两根桩之间的水平和竖向动力相互作用系数,并对桩间距与桩直径之比、两桩水平连线与荷载作用方向之间的夹角、桩—土刚度比和桩体长细比等参数对水平和竖向动力相互作用系数的影响进行了计算与分析;然后,运用动力相互作用系数的叠加原理分别对群桩的水平和竖向动力响应特性进行了分析,得到了群桩的整体位移、群桩的动力阻抗和各单桩分担的荷载;最后,针对具有代表性的2x2群桩和3X3群桩进行了算例分析。 4.将桩一土一结构祸合系统按线性体系考虑时,可以直接在频率域上进行动力响应分析,但对于非线性体系,由于桩基与上部结构之间的相互作用力表现为动力阻抗与输入地震动之卷积积分的形式,且动力阻抗依赖于激振频率,因此,在时域上直接进行桩一土一结构动力相互作用体系的地震响应分析就变得十分复杂和困难,目前对这个问题的研究尚不成熟。本文在对现有分析方法与计算模型综合分析的基础上,提出了一种改进的非线性动力V八刊目er模型,并运用最小二乘法,通过Matlab语言编程,确定了模型中各物理元件的参数,将桩基的动力阻抗用一系列与频率无关的弹簧、阻尼器、滑动块和集中质量等物理元件按某种串联或并联的组合模型来表达,从而为桩一土一结构祸合体系的非线性时域分析奠定了基础。 5.桩一土一结构相互作用体系的抗震性能分析是土木工程实践中一个非常复杂而且重要的问题。本文首先运用子结构分析方法,将上述桩基动力阻抗的研究成果和改进的非线性动力Winkler模型应用于桩基结构的抗震分析中;为便于进行对比验证分析,考虑桩一土相互作用效应,建立了桩基结构地震响应分析的整体有限元计算模型,通过对现有计算软件的二次开发,发展了桩一土一结构体系地震响应分析的整体有限元计算程序。然后,针对某一工程实例,分别运用子结构分析方法和整体有限元数值计算方法对桩一土一结构体系的地震响应特性进行了对比计算与分析,研究表明,两种方法所得到的计算结果是基本一致的,同时,得到了地震动的频谱特性和输入地震动的加速度幅值对桩基结构地震响应特性的影响规律,所得到的计算结果和有关结论将为桩基结构的抗震分析与工程设计提供参考依据。关键词:桩一土一结构体系;相互作用;单桩;群桩;非均质土层;弱化效应; 动力响应;动力阻抗;相对分离;相对滑移;动力Winkler模型;有限元 分析更多还原

【Abstract】 Because of its high strength, great bearing capacity and fine durability, pile foundations have been widely used in civil construction engineering such as high buildings, large workshops, hydraulic power stations, railways, highway roads, bridges, offshore platforms and nuclear power plants. However the dynamic interaction of pile-soil-structure system is very complex and there are some issues that have not been well solved in engineering practice. An intensive study is required for consideration on dynamic pile-soil-structure interaction effect in the analysis and design of pile-supported structures. Therefore the simplified and yet rational computational method and mechanical model for representation of lateral and vertical dynamic impedance function of piles, numerical method for evaluating dynamic response behavior of the interaction system of single pile or pile group and superstructure are mainly concerned in this dissertation. The main research and results involved in the dissertation includes the following parts.1. As one of the key issues in the study of dynamic behavior of pile-supported structures by the substructure method, the dynamic impedance of pile foundation should be rationally evaluated for considering the effect of soil-pile dynamic interaction. In this dissertation, based on a certain assumptions and the improved dynamic model of beam-on-Winkler’s foundation, a simplified mechanical model for computing the lateral and vertical dynamic impedance of single pile embedded in layered soils is established by using the principle of soil dynamics and structural dynamics. The softening effect of soils around pile during vibration and non-homogeneity of soil strata as well as the discontinuous behavior such as the de-bonding and relative slippage along pile-soil interface are simultaneously taken into account. It is shown through comparative study for a given example that the dynamic impedance of single pile numerically computed by the proposed method are relatively rational and can well agree with the computational and experimental results currently available. Finally the parametric studies are made for a wide ranges of main varied parameters involved to examine the effect of the softening area and softening degree of soils around pile, the contact conditions of pile-soil interface, the slenderness ratio of pile and the pile-soil stiffness ratio on dynamic impedances of single pile embedded in layered non-homogeneous soils.2. The dynamic response characteristics of single pile is one of the most important aspects in the study of dynamic pile-soil-structure interaction. In this dissertation, considering the softening effect of soils around pile and the non- homogeneity of soil strata simultaneously, a simplified analytical method for computing the lateral and vertical dynamic response characteristics of single pile to harmonic excitation is established. It is shown through the illustrative studies on a given example that the dynamic response of single pile numerically computed by the proposed method are rather reasonable and can well agree with the numerical solutions gained from finite element analysis by using well-known software. Finally the parametric studies are made for a wide range of main varied parameters to examine the effects of the softening area and softening degree of soils around pile, the mechanical conditions of soil strata, the slenderness ratio of pile and the pile-soil stiffness ratio on dynamic response characteristics of single pile embedded in non-homogeneous layered soils to harmonic loading with different excitation frequencies.3. In engineering practice, pile group is a widely applied form of pile foundation. Since the pile-soil-pile interaction effect should be taken into account for pile group, the dynamic response characteristics of pile group are much more complex than that ofsingle pile. Based on the definition and solving procedures of dynamic interaction coefficient and a certain assumptions, lateral and vertical dynamic interaction coefficients of two piles are compute更多还原