一种改进的Pasternak地基模型及层合地基板的解析解

从三维弹性力学基本方程出发,建立了正交异性材料层合板的状态方程,并提出一种改进的Pasternak弹性地基模型,给出了四边简支层合地基板的解析解。此解满足层合板的基本方程和层间连续条件,适合任意厚跨比,计及了所有材料常数,考虑了基底切向接触应力的影响。算例讨论了地基参数对几种地基模型的影响。计算结果表明,随着地基刚度的增大,剪应力的影响是不可忽略的。     

Coupled flexural and torsional vibrations of ship-like girders

The paper is related to investigation of coupled horizontal flexural and torsional vibrations of container vessels. Differential equations of coupled vibrations of a prismatic beam with open cross-section are derived. The equations are solved analytically by direct integration and by variational method. In the former case, the frequency equation is reduced to a polynomial of the fourth order. In the latter case, beam deflection and twist angle are assumed in the form of series of natural modes of uncoupled vibrations of free beam with suspended warping. The variational method manifests very fast convergence and high accuracy. Application of the developed methods is illustrated in the case of a prismatic pontoon with cross-section of a container vessel. The same numerical example is used for checking 1D FEM mathematical model and code developed for analyses of real structures of container vessels with variable cross-sections. In addition, correlation analysis of 1D and 3D FEM results is done to validate the accuracy of the former.     

框架结构与Winkler地基梁相互作用分析的新超元法

在文献[6]的基础上,提出了框架结构与Winkler地基梁相互作用分析的新超元法,导出了一种新的超级单元刚度矩阵。该超级单元刚度矩阵不仅反映了上部框架结构和基础梁的刚度贡献,而且反映了Winkler地基的刚度贡献。以此新的超级单元分析整体结构,提高计算精度,简化计算。     

桩基施工对临近建筑物的影响分析

本文对有争议的相邻桩基施工影响进行了分析判断,探讨了桩基施工对周围建筑影响的方式,经分析判断商住楼倾斜并非相邻桩基施工的直接影响造成的,并提出了降低桩基施工对周围建筑影响的方案,以供参考。     

地基基础与上部结构共同作用下的地基模型

综述了地基本构模型发展的历史、现状以及未来趋势，介绍了工程上常用的几种地基模型，并通过分析各类本构模型的优缺点，确定了其应用范围。     

框架结构及筏基与边坡地基共同作用的受力分析

随着山地城镇建设的发展,一些建筑不得不建于边坡地基之上,边坡地基与建筑结构之间的共同作用成为一个现实的研究课题。通过有限元数值分析的方法,对某框架结构及筏基与边坡地基的共同作用受力问题进行了计算分析,其中边坡地基坡高10m,坡度为2：1,上部建筑为10层的框架结构。共同作用分析中上部结构、基础与边坡地基满足三者的受力平衡和变形协调条件。研究了考虑共同作用后的边坡地基强度变形情况及上部框架结构及筏板基础内力和变形情况,得出了对工程实践有参考意义的结论。     

Alternative solution for kinematic interaction problem of soil–structure systems with embedded foundation

An effective procedure to incorporate kinematic interaction (KI) aspects in seismic analysis of soil–structures systems was presented. In this regard, first, the effect of KI on the structural response was investigated with special focus on the role of rocking component of foundation input motion (FIM). This was performed parametrically for a wide range of selected nondimensional parameters, which well define the introduced simplified soil–structure model. It was observed that ignoring the effect of rocking input motion may introduce errors, which can be on the unsafe side especially for slender structures with large embedment ratios. On the other hand, it was known that introducing the rocking input motion makes the problem too complicated to be addressed by simplified guidelines suitable for seismic codes or practicing engineers. As an alternative solution, a modified translational input motion was introduced, which can replace both translational and rotational components of FIM. This modified input motion, which was referred to as the net horizontal (NH) FIM in this article, was generated such that the roof displacement of the soil–structure system to this motion is identical to that of the same model subject to the multicomponent FIM resulted by KI. The applicability of the proposed procedure was then examined for a wide range of soil–structure systems subjected to a couple of real ground motions. Copyright © 2010 John Wiley & Sons, Ltd.     

Vibration of prestressed thin cylindrical shells conveying fluid

A general approach to modelling the vibration of prestressed thin cylindrical shells conveying fluid is presented. The steady flow of fluid is described by the classical potential flow theory, and the motion of the shell is represented by Sanders’ theory of thin shells. A strain–displacement relationship is deployed to derive the geometric stiffness matrix due to the initial stresses caused by hydrostatic pressure. Hydrodynamic pressure acting on the shell is developed through dynamic interfacial coupling conditions. The resulting equations governing the motion of the shell and fluid are solved by a finite element method. This model is subsequently used to investigate the small-vibration dynamic behaviour of prestressed thin cylindrical shells conveying fluid. It is validated by comparing the computed natural frequencies, within the linear region, with existing reported experimental results. The influence of initial tension, internal pressure, fluid flow velocity and the various geometric properties is also examined.     

新旧房屋相接处基础处理的设计实例探讨

结合具体工程实例，从概念设计的角度介绍了如何在实践中理解和运用桩基和筏基处理新旧建筑基础衔接问题，做到既满足建筑设计要求又保证新旧房屋结构的安全。     

深水桥墩流固耦合下的自振特性研究

首先探讨了深水桥墩流固耦合下动力特性研究的有限元理论和建立计算模型的方法。研究了桥墩墩水耦合分析中流体单元网格尺寸、流体范围对深水桥墩动力特性数值解精度的影响,得出了工程中常见的墩水耦合分析较优水体单元尺寸和理想水体范围图。计算分析了矩形、圆形和圆端型截面深水桥墩的自振特性,实心墩在水中的自振频率降低10%～20%之间。空心墩频率降低幅度大于实心墩,与截面尺寸和壁厚密切相关。水体对空心墩的振型也有一定影响。进一步研究了淹没深度、桥墩截面尺寸以及空心墩壁厚对深水桥墩频率降低幅度的影响,得到有益的结论。该研究方法以及相关结论可以对墩水耦合问题的进一步研究以及工程应用提供参考。     

中心岛法支护结构内力及变形计算的地基反力法

中心岛施工法中预留土台具有减小围护结构内力和变形、节约成本、设置灵活等优点在工程中应用日益广泛,然而预留土台作用下围护结构的计算方法还不成熟。本文基于Winkler弹性地基反力法,根据围护结构沿竖向受力模式的不同,提出了一种新的计算分析模型及控制方程组,推导了围护结构内力及变形计算的数学解析解矩阵表达式,并给出解析解解答方法。最后,编制Matlab计算程序进行围护结构内力及变形计算,并与现场监测数据结果进行对比分析来验证解析方法的可靠性,结果证明该方法能够准确计算中心岛施工法围护结构内力及变形。     

基坑支护结构稳定性问题的模糊随机方法研究

鉴于基坑支护结构的稳定性问题同时具有随机性和模糊性的特点,随机性问题可以采用结构可靠度理论研究,而模糊性问题可以采用模糊数学方法研究,重点研究了包含各种模糊性因素的模糊目标稳定可靠指标的确定方法。实例计算结果表明,兼顾随机性和模糊性的基坑稳定性问题分析方法,其相应的可靠指标应适当提高,这与工程实际情况是相吻合的。     

筏板基础设计与计算方法的讨论与研究

从筏板基础设计方法的发展阶段出发,阐述了简化计算方法、基础板理论分析法、共同作用分析方法三种设计方法的思路,并介绍了共同作用分析方法的几种主要分析方法,以便合理地选择筏板基础的设计方法.     

Influence of soilestructure interaction on seismic collapse resistanceof super-tall buildings

Numerous field tests indicate that the soilestructure interaction （SSI） has a significant impact on thedynamic characteristics of super-tall buildings, which may lead to unexpected structural seismic responsesand/or failure. Taking the Shanghai Tower with a total height of 632 m as the research object, thesubstructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower. Therefined finite element （FE） model of the superstructure of Shanghai Tower and the simplified analyticalmodel of the foundation and adjacent soil are established. Subsequently, the collapse process of ShanghaiTower taking into account the SSI is predicted, as well as its final collapse mechanism. The influences ofthe SSI on the collapse resistance capacity and failure sequences are discussed. The results indicate that,when considering the SSI, the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved, with a corresponding decrease of the seismic demand.In addition, the SSI has some impact on the failure sequences of Shanghai Tower subjected to extremeearthquakes, but a negligible impact on the final failure modes.
2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.     

Comparison of the dynamic responses of monopiles and gravity base foundations for offshore wind turbines in sand using centrifuge modelling

Monopiles and gravity base foundations (GBF) are two of the most commonly used foundations for offshore wind turbines. As resonance can cause damage and even failure of wind turbines, understanding the difference between the dynamic responses of monopiles and GBFs under free vibration is important. However there is little experimental data regarding their natural frequency, especially from model tests carried out at correct stress levels. This paper presents the results of novel monopile and GBF tests using a centrifuge to directly determine the natural frequency (f_n) of the foundation-soil system. The natural frequencies of wind turbine monopiles and GBFs in centrifuge models were measured during harmonic loading using a piezo-actuator, with the results confirming that soil-structure interaction must be considered to obtain the system’s natural frequency as this frequency reduces substantially from fixed-base values. These results will contribute in preventing resonance induced damage in wind-turbines.     

基于特尔菲–理想点法的隧道围岩分类研究

基于理想点法的基本原理,选取岩石单轴饱和抗压强度Rc、岩石质量指标RQD、岩体完整性系数Kv、结构面强度系数Kf、地下水渗水量ω作为评价指标,通过特尔菲科学方法确定其权重系数,建立隧道围岩分类模型,并利用广州抽水蓄能电站第1期工程围岩实测资料进行模型检验。结果表明:特尔菲–理想点法判别结果与实际围岩类别大致相同,且和人工神经网络判别结果、突变级数法判别结果基本符合,从而验证了特尔菲–理想点法用于围岩分类是可行的。最后,运用建立的特尔菲–理想点法围岩分类模型对浙江省诸永高速公路西华岭隧道围岩类别进行判别,经计算分析发现,所选洞段围岩判定结果与设计围岩类别相吻合,进一步证明了该方法用于隧道围岩分类的合理性和有效性。这一方法在西华岭隧道中的成功应用,不仅可以为该隧道设计、施工提供参考,同时对以后同类隧道工程围岩分类有一定的参考价值。     

长春市某建筑基坑支护结构事故原因的分析

长春市某12m深基坑采用排桩锚杆支护结构,因土压力分析有误,支护结构设计不合理,导致基坑大部分开挖到基底后,排桩结构水平位移超过允许范围,桩间土大面积掉落,基坑外地面出现地裂缝,由槽钢组成的腰梁扭曲变形,桩顶冠梁向基坑内变形明显,并出现裂缝。由于施工单位及时采取回填反压措施,才控制住支护结构的变形。然后,通过进一步的理论分析,并对原支护结构增加一排锚杆后,基坑开挖才得以顺利进行。     

圆形结构下筏式基础变形反力分布规律试验研究

通过大型室内模型试验,指出圆形结构的荷载呈放射状传递到地基,当荷载与基础的相对挠曲呈线性关系时,柔性基础的基底反力、基础变形在结构外的2.5倍基础厚度范围内都是均匀分布的。柔性基础在破坏前的相对挠曲是逐渐增加的,而刚性基础在破坏时基础的相对挠曲突然增大。柔性基础的基底反力始终是中心点反力最大;刚性基础的中心点处基底反力小于周边基础反力。研究表明,基础变形、反力分布与基础和上部结构的刚度及形状有关,基础刚度越大,其调整基础变形、反力分布的能力越大。     

基坑开挖对坑内工程桩的影响及保护初探

采用有限差分软件FLAC对基坑开挖过程进行了模拟,研究了不同开挖工况下的工程桩受力特性,针对分析结果,研究了对工程桩加以保护的防护措施,并分析了水泥土搅拌桩的加固效果,以供同类工程施工参考。