Ramberg-Osgood土动力非线性模型在 ABAQUS软件上的开发及应用

基于ABAQUS有限元软件开发平台,对Ramberg-Osgood土动力非线性本构模型进行了修正。通过合理的假设得出了模型修正参数?、R的取值方法和算法。滞回曲线加卸载规律符合修正后的Masing准则。并进行了三维场地地震动非线性分析,分析了不同输入峰值的地震波对土体应力-应变关系的影响,并与一维场地动力分析Shaking程序的计算结果进行了比较。分析结果表明,非线性分析时的水平位移和相对位移要大于等效线性情况下的相应位移,这表明采用何种本构关系将影响到得到的场地的地震动反应结果,因此,在工程应用时需加以合理的选择,并对最终结果做出合理的判断     

岩体结构面新型本构模型研究

对于涉及需要单独考虑岩体结构面的工程岩体结构分析,采用能反映岩体结构面主要力学特性的合理的本构模型是取得合理解答的关键问题之一。针对在经典连续介质力学理论框架内建立岩体结构面本构模型的缺点,基于岩体结构面的实际受力变形特性,采用直接法建立了一种新型岩体结构面本构模型。所建立的模型依据岩体结构面切向应力变形曲线及剪胀曲线的实际特征,将其分为峰前线性段、峰前非线性段以及峰后软化段,并分别给出了用于描述岩体结构面变形和强度等主要力学特性的数学模型,进而推导建立了结构面各变形阶段的增量型本构模型。最后,编写相关计算程序,采用所建立的新型本构模型以及被广泛采用的Plesha模型对经典的岩体结构面直剪试验成果进行拟合分析。结果表明,所建立的新型本构模型能更为合理的描述岩体结构面的主要力学特性,且模拟能力优于Plesha模型     

刚性桩复合地基-上部结构动力相互作用体系抗震性能及影响因素分析

通过模拟土的非线性动力本构模型,选取合理的人工边界及耦合阻尼模型,建立了刚性桩复合地基与上部结构相互作用体系三维有限元动力分析模型。通过计算,对比了刚性桩复合地基与普通桩基对上部结构地震反应的影响异同,同时得到了土体模量与分层、基础埋深、桩径与桩长、砂石垫层模量与厚度以及上部结构特性等因素在考虑土-结构动力相互作用时对刚性桩复合地基抗震性能的影响及其基本规律,并与已有相关试验结果进行了对比,得到较好验证。研究结果为工程设计与工程应用提供了可借鉴的理论依据。     

堆石料三维边界面模型在FLAC3D中的开发与验证

堆石料三维边界面模型结合了统一非线性强度准则,可以反映三维应力空间堆石料的应变硬化、软化以及体积收缩和剪胀等传统本构模型难以反映的力学特性。基于三维边界面模型的基本理论,通过FLAC3D提供的二次开发平台,在VC++环境下实现了三维边界面本构模型的二次开发,并给出基于FLAC3D程序的边界面本构模型开发的关键步骤、编程要点和调试方法。利用开发的本构模型,开展了三轴压缩试验的数值模拟计算,并与理论值进行了对比分析。结果表明,嵌入在FLAC3D中的三维边界面本构模型能够较好地反映设定试验条件下的材料性能,而且三维边界面本构模型模型参数简单,都可从常规三轴试验获得,从而验证了三维边界面模型二次开发程序的优越性与合理性。     

对土体动力黏塑性记忆型嵌套面模型的改进

在对土体动力黏塑性记忆型嵌套面本构模型已有的研究基础上,对该模型进行改进,不再对空间锥形屈服面变化时屈服面锥角 的变化规律作假定,按照土体在循环荷载作用下空间屈服面在子午平面上投影线的实际变化规律,建立屈服面硬化参数的增量表达式,完善了该模型的理论基础,为进一步对该模型的试验验证和改进提供了理论依据,并对比分析了分别使用改进后模型和改进前模型计算同一场地地震反应的计算结果。     

考虑颗粒破碎效应的堆石料静动力本构模型

为合理反映颗粒破碎对堆石料力学特性的影响,基于试验结果分析,得出了堆石料在压缩和剪切作用下的颗粒破碎特性规律。通过引入压缩破碎和剪切破碎的相关参数,借鉴已有本构模型的合理定义,吸收临界状态理论和边界面理论的优点,发展了考虑颗粒破碎和状态相关的堆石料静动力统一弹塑性本构模型,并阐述了模型参数的确定方法。该模型不仅能够反映堆石料在静力荷载作用下的低压剪胀、高压剪缩、应变软化和硬化等特性,还能够反映在循环荷载作用下应力-应变的滞回特性和残余变形的累积效应。最后为验证模型的合理性,分别对堆石料的静力三轴和循环三轴试验进行了数值模拟预测,结果表明：模型预测与试验数据吻合良好,所提出的本构模型能够合理地描述颗粒破碎对堆石料静动力变形特性的影响。     

粘弹塑本构模型及用于冻土数值计算的柔度矩阵

随着寒区经济发展及冻结法施工技术在工程中的推广应用,对冻土蠕变的深入研究显得尤为重要.对冻土单轴流变试验结果分析,用非线性牛顿体替代线性牛顿体,从而对西原模型进行了改进,得到了冻土三向应力状态下的本构方程;并利用D-P屈服准则推导出应用与数值计算的柔度矩阵.通过有限元程序的二次开发,将本构模型添加到大型非线性程序ADINA中.用三轴蠕变试验检验了粘弹塑本构模型,获得相应的试验拟合曲线.结果表明:三轴蠕变试验与理论计算结果吻合良好,说明粘弹塑本构模型可以描述冻土在高应力下反映的非衰减性蠕变变形特征.     

考虑试验阻尼效应的一种土体动力双型抛物线本构模型

针对土动力试验中土体反向卸载（或加载）曲线形状有时表现为先变化平缓后变化剧烈这一特征,基于土体实验结果的 和 曲线,建立了不规则荷载作用下可调的双型抛物线形式的本构曲线规则,阐述了A型和B型抛物线的函数表达式及实现过程。采用9种方法对试验阻尼比的模拟对比,表明所建立的加卸载准则尤其能准确拟合试验阻尼值,是对广义Masing准则的一种简化及实用化。由于调制因子 的可变性,它具有更强地模拟试验本构曲线形状的能力。针对台湾Lotung DHB钻井台阵试验场地,以等效线性化方法SHAKE91、LSSRLI-1,时域非线性方法DESRA-2、Pyke方法、非Masing准则模型1、“隐式应力阻尼等效”模型、“阻尼比退化系数”模型和非Masing准则模型2以及双型抛物线本构模型等9种方法（或模型）分别进行了非线性地震反应分析,并将结果与强震观测记录进行比较,结果表明,双型抛物线本构模型计算的复合加速度地震动的峰值大小、波形大小相对关系及后续波形,与实际地震记录较相一致,说明了模型的合理性以及实际工程应用的可行性。     

深厚覆盖层上土石坝抗震分析的三维真非线性方法及应用

针对强震区深厚覆盖层上土石坝工程的特点,基于土石料三维粘弹塑性动力本构模型,考虑孔隙水压力消散和扩散,建立了深厚覆盖层上土石坝地震反应分析的三维真非线性有效应力动力分析方法及抗震安全评价方法。利用土石料动力特性的大型三轴试验成果,对一深厚覆盖层上的土石坝进行了地震反应分析,给出了坝体及覆盖层地基的加速度反应、应力反应,并结合单元抗震安全系数、防渗墙动应力、地震残余变形、坝坡动力稳定性等进行了抗震评价,为大坝的抗震设计提供了有力的技术依据。     

一种土的非线性弹性本构模型参数的反演方法

旨在提出一种土的非线性弹性本构模型参数反演的方法。以现今普遍实行的地基载荷试验为基础,依据遗传算法的组合优化理论,采用正演计算和遗传算法优化相结合的方式,建立了土层非线性弹性本构模型参数反演的方法;并依据某黄土场地地基载荷试验数据,实施了黄土土层非线性弹性本构模型参数反演的全过程。计算结果表明,所建立的方法可以实现土层非线性弹性本构模型中相互关联的多个参数的组合优化,并在对初始值要求较低的情况下,可以获得良好的参数反演精度。从而为土的变形特性分析和土与其中及相邻结构的共同作用分析,提供了较好的土体本构模型参数的确定方法。     

岩土材料塑性损伤模型及拱坝的变形局部化分析

常规的弹塑性模型难以模拟材料破坏时由于内部损伤累积引起的变形局部化带形成过程。将岩土材料抽象为含有孔洞的球形体胞单元的集合体,采用一个标量--孔洞体积百分比来刻划单元的损伤程度,基于细观损伤力学提出了一个适用于岩土材料的塑性损伤模型。将该模型通过用户子程序嵌入到大型有限元商业软件MRAC中,研究岩土材料的局部化剪切带形成过程。采用该模型,成功地对平面应力条件下岩土材料单轴受压和单轴受拉试件的局部化破坏分别进行了数值模拟。采用该模型,对拱坝在超水载作用下的变形局部化进行了研究,数值计算结果表明,上游坝踵处最先发生变形局部化现象。     

Nonlinear Site Response and Liquefaction Analysis in the New Madrid Seismic Zone

Many existing highway bridges in the New Madrid Seismic Zone are located in the Mississippi Embayment, consisting of deep soil deposits and liquefaction susceptible near surface soils. It is important to understand the comprehensive impact of deep soil deposits and liquefaction on the response of the bridge foundations under seismic loading. A nonlinear soil model is then presented to study the impacts of the deep soil deposit and liquefaction on response analysis. The soil model has the advantage of using input parameters that can be obtained from conventional field and laboratory testing methods, which makes it attractive to engineering practice. The model calibrations used field recorded motions and laboratory test data, which indicate that the model provides an acceptable outcome based on simple input parameters. The model is implemented into the site response analysis for a typical Missouri highway bridge site in this seismic zone. The effect of the deep soil deposit and liquefaction on the site response analyses is discussed.     

Boundary setting method for the seismic dynamic response analysis of engineering rock mass structures using the discontinuous deformation analysis method

Large deformations and discontinuous problems can be calculated using the discontinuous deformation analysis (DDA) method by solving time steps, and this method is suitable for simulating the seismic dynamic response of engineering rock mass structures. However, the boundary setting must be carefully analyzed. In this paper, four boundary settings for the DDA method are investigated. First, the contributions to the DDA equations for nonreflecting boundaries (including the viscous boundary and the viscoelastic boundary) are deduced based on the Newmark method. Second, a free‐field boundary is introduced in the DDA method with boundary grid generation and coupling calculation algorithms to accurately simulate external source wave motion, such as earthquakes. Third, seismic input boundary treatments are intensively examined, and the force input method is introduced based on nonreflecting boundaries. Finally, the static‐dynamic unified boundary is implemented to ensure consistent boundary transformation. The boundary setting method in the DDA method is discussed, and the suggested treatments are used to analyze the seismic dynamic response of underground caverns. Copyright © 2015 John Wiley & Sons, Ltd.     

沉积地质学发展新航程——地震沉积学

地震沉积学是在地震地层学和层序地层学基础上发展起来的、沉积地质学与地球物理学相互交叉的新兴学科,在刻画薄层砂体、表征储集层和预测岩性圈闭等方面发挥了重要作用。在表述地震沉积学发展简史的基础上,介绍了地震沉积学的基本概念、基本原理和主要研究流程;在建立精细层序地层格架基础上,重点阐述了90°相移、分频处理与频谱分解、属性优选、地层切片、地球物理反演、地震岩性解释和RGB(红色、绿色、蓝色)地震属性融合等地震沉积学关键技术以及地震沉积相实例分析。认为中国地震沉积学应该围绕不同类型沉积盆地开展油气勘探阶段地震地貌学(地震沉积相模式)和复杂(多样)地震岩性学综合研究,在油气开发阶段,充分利用RGB地震属性融合等多种地球物理方法技术,开展多种成因类型砂体构型和储集层定量表征研究。综合研究表明,地震沉积学是沉积地质学发展的新航程。     

Proposed seismic hazard maps of Sumatra and Java islands and microzonation study of Jakarta city,Indonesia

This paper presents the development of spectral hazard maps for Sumatra and Java islands, Indonesia and microzonation study for Jakarta city. The purpose of this study is to propose a revision of the seismic hazard map in Indonesian Seismic Code SNI 03-1726-2002. Some improvements in seismic hazard analysis were implemented in the analysis by considering the recent seismic activities around Java and Sumatra. The seismic hazard analysis was carried out using 3-dimension (3-D) seismic source models (fault source model) using the latest research works regarding the tectonic setting of Sumatra and Java. Two hazard levels were analysed for representing 10% and 2% probability of exceedance (PE) in 50 years ground motions for Sumatra and Java. Peak ground acceleration contour maps for those two hazard levels and two additional macrozonation maps for 10% PE in 50 years were produced during this research. These two additional maps represent short period (0.2 s) and long-period (1.0 s) spectra values at the bedrock. Microzonation study is performed in order to obtain ground motion parameters such as acceleration, amplification factor and response spectra at the surface of Jakarta. The analyses were carried out using nonlinear approach. The results were used to develop contour of acceleration at the surface of Jakarta. Finally, the design response spectra for structural design purposes are proposed in this study.     

地下综合管廊地震动力响应三维数值分析

综合管廊由于埋深较浅,在抗震分析中应考虑Rayleigh波的作用,为研究Rayleigh波与底部地震加速度共同作用下综合管廊的动力响应特征,建立双仓的综合管廊三维动力有限元数值模型,土体采用考虑滞回环特性的高级本构模型（HSS模型）,通过边界上多次脉冲荷载生成Rayleigh波,模型底部横向分别作用Upland波、Kobe波、Taft波,并与仅考虑底部横向作用的常规时程分析进行对比。研究表明:综合管廊结构的横向动力响应主要受横向地震波影响,结构纵向动力响应受沿其轴向入射的Rayleigh波影响相对较大;采用Rayleigh波+底部地震波的输入方法比单独底部地震波输入得到的结构动力响应整体上要更显著一些;输入不同的地震加速度时程,管廊动力反应规律相似,但综合管廊结构影响大小有差异,可见底部地震波与地表Rayleigh波作用的匹配程度对结构动力响应结果有一定影响。研究成果可供地下综合管廊结构地震动力响应精细化数值分析及抗震设计参考。     

三维生物礁滩建模及地震数值模拟

基于塔礁、点礁、生物滩等地质体的几何特征及地质特征,采用高精度的三维块状建模方法,建立了适合于复杂地区的三维礁滩复合体模型。该模型不但立体地反映了生物礁、生物滩及地层间的空间展布特征,还可以直观地体现了生物礁滩储层内部的物性差异。此外采用FK域三维波动方程数值模拟方法对其进行了地震波场数值模拟,得到了一系列具有代表性时间剖面上的地震波场响应特征,为正确认识实际生物礁滩的复杂结构和特性提供了依据。     

Methodology for benefit–cost analysis of seismic codes

A number of high-profile seismic events have occurred in recent years, with a wide variation in the resulting economic damage and loss of life. This variation has been attributed in part to the stringency of seismic building codes implemented in different regions. Using the HAZUS Earthquake Model, a benefit?Ccost analysis was performed on varying levels of standard buildings codes for Haiti and Puerto Rico. The methodology computes expected loss assuming a Poisson event process with lognormally distributed event magnitude and idealized damage?Cmagnitude response functions. The event frequency and magnitude distributions are estimated from the historical record, while the damage functions are fit using HAZUS simulation results for events with systematically varying magnitudes and different seismic code levels. To validate the approach, a single-event analysis was conducted using alternative building codes and mean magnitude earthquakes. A probabilistic analysis was then used to evaluate the long-term expected value for alternative levels of building codes. To account for the relationship between lives saved and economic loss, the implicit cost of saving a life is computed for each code option. It was found that in the two areas studied, the expected loss of life was reduced the most by use of high seismic building code levels, but lower levels of seismic building code were more cost-effective when considering only building damages and the costs for code implementation. The methodology presented is meant to provide a basic framework for the future development of an economic-behavioral model for code adoption.     

Numerical prediction of tunnel performance during centrifuge dynamic tests

In this paper, a comparison between numerical analyses and centrifuge test results relative to the seismic performance of a circular tunnel is provided. The considered experimental data refer to two centrifuge tests performed at Cambridge University, aimed at investigating the transverse dynamic behaviour of a relatively shallow tunnel located in a sand deposit. For the same geometry, different soil relative densities characterise the two tests. The four seismic actions considered, of the pseudo-harmonic type, are characterised by increasing intensity. The 2D numerical analyses were performed adopting an advanced soil constitutive model implemented in a commercial finite element code. The comparison between numerical simulations and measurements is presented in terms of acceleration histories and Fourier spectra as well as of profiles of maximum acceleration along free-field and near-tunnel verticals. In addition, loading histories of normal stress and bending moments acting in the tunnel lining were considered. In general, very good agreement was found with reference to the ground response analyses, while a less satisfactory comparison between observed and predicted results was obtained for the transient and permanent loadings acting in the lining, as discussed in the final part of the paper.     

Lessons learned from two case histories of seismic microzonation in Italy

The prediction of the variability of the seismic ground motion in a given built-up area is considered an effective tool to plan appropriate urban development, to undertake actions on seismic risk mitigation and to understand the damage pattern caused by a strong-motion event. The procedures for studying the seismic response and the seismic microzonation of an urban area are well established; nevertheless, some controversial points still exists and are discussed here. In this paper, the selection of a reference input motion, the construction of a subsoil model and the seismic response analysis procedures are discussed in detail, based on the authors’ experience in two Italian case histories: the seismic microzonation of the city of Benevento, which was a predictive study, and the simulation of seismic response and damage distribution in the village of San Giuliano di Puglia, which was a retrospective analysis.