高墩抗震梁桥单墩模型地震时程响应分析

直接基于经典的欧拉梁理论,推导针对规则高墩梁桥单墩模型弹性阶段地震时程响应的半解析计算步骤,考虑梁墩铰接的形式,在墩底引入等效基础弹簧变形协调条件,解析的获得各阶实模态和频率方程,用牛顿法搜索各阶频率．应用振型叠加法求解体系的地震时程响应。最后应用该方法对一高墩梁桥单墩模型的地震响应进行分析,与离散模型的有限元时程积分的结果比较表明了方法的有效性。     

非平整曲面隔震结构的多质点计算模型及地震响应研究

针对强地震作用下隔震结构隔震层变形过大的现象提出了曲面隔震结构体系,该结构隔震层为曲面布置,在地震和结构重力作用下,上部结构可绕曲率中心进行曲面运动。建立了非平整曲面隔震结构多质点计算分析模型,通过数值分析进一步研究非平整曲面隔震层的曲率半径对结构地震响应的影响规律。分析结果表明:在罕遇地震作用下,曲面隔震结构对隔震层及上部结构的位移控制效果显著,同时当曲率半径为10~15倍重心高度时具有良好的隔震效果。     

近断层地震特性对隔震曲线连续梁桥地震响应的影响

为研究近断层地震动对曲线连续梁桥地震响应及碰撞效应的影响,采用非线性时程分析法,分别研究脉冲效应、上盘效应及方向性效应对某三跨曲线连续梁桥支座位移、桥墩内力及邻梁间碰撞力的影响;通过支座隔震率的对比分析,探究不同类型近断层地震动下地震响应产生差异的原因。研究结果表明:脉冲效应、上盘效应和方向性效应均会增大曲线连续梁桥地震响应,脉冲效应的影响尤为显著;脉冲效应和方向性效应削弱了高阻尼橡胶支座的隔震特性,而上盘效应对桥梁响应的影响仅与上盘地震动自身特性有关;综合来看,脉冲效应对曲线梁碰撞响应影响最明显,上盘效应影响不大。     

多维地震激励下曲线梁桥简化模型及最不利输入方向研究

曲线梁桥只有在某一特定方向输入地震动时,结构某点或某截面的内力(或应力)才能达到最大值,需要沿多个可能方向输入计算才能确定地震动最不利输入方向。根据隔震曲线梁桥受力特点,将桥梁上部结构和桥墩简化均具有两个水平自由度和一个围绕质量中心轴扭转自由度的堆积质量模型,建立双质点六自由度简化分析模型,通过求解曲线梁桥的动力学方程研究结构的动力特性和地震动行为。算例表明,双质点模型计算结果与传统的有限元模型基本一致,且计算方法简单,可以考虑各种敏感因素的影响,借助编程更适合提出规律性的设计方法。进而在双质点模型基础上应用MATLAB编程探讨多维地震作用下曲线梁桥地震波最不利输入方向的问题,针对不同参数的隔震曲线梁桥,改变相关参数后只需运行一次就可以实现最不利输入角度的确定,可为有限元法最不利地震波输入方向的确定提供参考,并大大减少多个方向输入试算的工作量。     

多跨简支规则直线梁桥横桥向地震反应合理简化计算模型研究

以多跨简支的直线梁桥为研究对象,在对比分析主要抗震国家现行桥梁抗震设计规范关于结构横向地震反应计算所采用的简化方法的基础上,通过变化跨径比、墩高、桥墩刚度比等主要结构设计参数,对刚性梁模型与柔性梁模型在模拟结构横桥向地震反应方面的合理性进行比较,提出了适用于多跨简支规则直线梁桥横向地震反应计算的合理简化模型,并对简化计算方法进行改进。     

罕遇地震下村镇建筑复合隔震系统的地震响应特征及设计参数

为研究罕遇地震下复合隔震村镇建筑的地震响应特征及设计参数,采用ABAQUS有限元软件建立了复合隔震结构、滑移隔震结构、砂垫层隔震结构以及传统的砌体结构四种模型,通过对比4种模型在不同滑移层摩擦系数及不同地震烈度下的加速度、位移及底部剪力等动力响应差异,得出复合隔震体系的地震响应特征及主要设计参数。结果表明:复合隔震体系具有最优的隔震效果,且滑移层摩擦系数越小,地震烈度越大,隔震效果越好。根据预设40%隔震率的要求,确定出不同抗震设防烈度区的滑移层摩擦系数取值范围。     

SMA弹簧-摩擦支座基础隔震体系的地震响应分析

大尺寸超弹性形状记忆合金(Shape Memory Alloy,简称SMA)螺旋弹簧是一种可用于结构减振控制的阻尼器。然而,迄今为止这种超弹性阻尼器在土木工程结构隔震领域的研究较少。本文提出了一种SMA弹簧-摩擦支座(SMA Spring-Friction Bearing,简称SFB)并研究了其隔震性能。首先,在考虑材料内部相变过程的SMA本构关系模型的基础上,针对超弹性SMA弹簧的恢复力性能建立了一种便于工程应用的新的宏观现象模型。随后,推导了SFB隔震结构体系运动方程,利用MATLAB程序进行了结构地震响应的数值模拟。最后,将SFB隔震体系的地震响应与具有相同结构参数的纯摩擦支座(Pure Friction Bearing,简称PFB)隔震体系和摩擦摆(Friction Pendulum System,简称FPS)隔震体系的地震响应进行了对比分析。研究结果表明,SFB对上部结构具有良好的加速度减振效果,同时,该支座较其它两种滑动支座在降低隔震层位移峰值响应和抑制隔震支座残余位移两方面具有明显的优势。     

桩-土-结构体系随机地震响应的实用计算方法及参数分析

考虑地震的随机性和土体的非线性,引入粘弹性边界,提出了一种在谐响应分析中直接输入加速度的加载方式,建立了基于虚拟激励法、等效线性化法和确定性动力有限元法相结合的非线性桩-土-结构体系随机地震响应的实用计算方法.采用该法对单桩支承的剪切型结构进行了较为全面的参数分析.结果表明基岩地震动输入水平,桩长度和土体模量都对结构反应有较大影响.该方法可方便的用于随机地震下桩-土-结构体系的参数分析中.     

结构-层序模型的地震响应及在油气勘探中的应用

结构-层序分析方法借助结构-层序模型和时频 分析技术,通过对地震剖面的定量分析,建立层序 体与时频特征、储层含油性与时频能量间的对应 关系,结合地质、测井、钻采等多种资料,对勘探 目的层进行层序分析、旋回划分、储集层预测及目 标定量描述。结构-层序分析的基础是建立有效 结构-层序模型和其地震响应特征,在此基础上, 将结构-层序分析技术应用于陆相断陷盆地的陡 坡带砂砾岩体、缓坡带三角洲、低位扇体以及其它 隐蔽油气藏的勘探,取得了较好的勘探效益。     

松辽盆地营城组火山机构-岩相带的地震响应

松辽盆地徐家围子断陷多期次喷发的火山岩在纵向和横向上相互叠置,造成火山岩地震响应特征复杂,影响了对火山岩储层的地震预测精度和地质规律的认识.本文基于钻井和连片三维地震资料,结合区域构造认识,建立了徐家围子断陷营城组火山机构-岩相带的地震响应模式,并利用相干体和地层切片等属性分析技术实现了火山机构-岩相带的空间识别.从火山口到远源相带火山岩体非均质性减弱,在三维相干体切片上表现为相干属性变化率的降低.研究区主要发育四种火山机构-岩相带,其地震响应特征分别为,①火山口穹窿多种岩相迭合相带:表现为杂乱反射带、自下而上呈放射状、围绕火山喷口厚度向外减薄、相干性强、剖面和平面形态多变;②近源爆发相与溢流相叠置相带:具有断续层状、中强振幅、低频反射特征,呈环带状围绕火口中心相带分布;③远源爆发相带:火山机构一侧具有上拱的板状外形,表现为楔形层状连续中强振幅反射特征;④远源火山沉积相带:具有板状外形,亚平行反射结构,能量较强和同相轴连续的响应特征.这些反射特征是火山作用喷出物堆积过程中,内部层结构和层形态呈规律性变化的地震表象.     

规则桥梁抗震性能水准的定义及其量化描述

基于性能的结构抗震设计是各国结构抗震设计规范未来的主要发展方向,虽然其理论框架已基本形成,然而其中至关重要的结构抗震性能水准的定义及其量化描述问题,目前仍处于研究探讨阶段.本文从公路梁式桥震害现象出发,采用极限状态设计概念,对规则桥梁在地震作用下的性能水准予以明确的定义;并以墩顶漂移率作为设计参数,通过对大量试验数据的...     

基于复阻尼模型的连续刚构桥地震响应分析

为了研究复阻尼模型下连续刚构桥的地震响应,文章讨论了利用复阻尼模型求解连续刚构桥地震响应的方法,并按相同的阻尼比,分别采用复阻尼模型和黏性阻尼模型计算了后渚连续刚构桥在不同地震动作用下的响应,将计算结果进行对比,分析了两种不同的阻尼模型对地震响应影响的差别。结果表明,采用不同类型的阻尼对地震响应影响很大,以复阻尼计算出的响应幅值作为设计值,更加偏于安全,对于保证桥梁结构的抗震安全更可靠。     

Engineering characteristics of near-fault vertical ground motions and their effect on the seismic response of bridges

A wide variety of near-fault strong ground motion records were collected from various tectonic environments worldwide and were used to study the peak value ratio and response spectrum ratio of the vertical to horizontal component of ground motion, focusing on the effect of earthquake magnitude, site conditions, pulse duration, and statistical component. The results show that both the peak value ratio and response spectrum ratio are larger than the 2/3 value prescribed in existing seismic codes, and the relationship between the vertical and horizontal ground motions is comparatively intricate. In addition, the effect of the near-fault ground motions on bridge performance is analyzed, considering both the material nonlinear characteristics and the P~? effect.     

Performance spectra based method for the seismic design of structures equipped with passive supplemental damping systems

A new direct performance‐based design method utilizing design tools called performance‐spectra (P‐Spectra) for low‐rise to medium‐rise frame structures incorporating supplemental damping devices is presented. P‐Spectra are graphic tools that relate the responses of nonlinear SDOF systems with supplemental dampers to various damping parameters and dynamic system properties that structural designers can control. These tools integrate multiple response quantities that are important to the performance of a structure into a single compact graphical format to facilitate direct comparison of different potential solutions that satisfy a set of predetermined performance objectives under various levels of seismic hazard. An SDOF to MDOF transformation procedure that defines the required supplemental damping properties for the MDOF structure to achieve the response defined by the target SDOF system is also presented for hysteretic, linear viscous and viscoelastic damping devices. Using nonlinear time‐history analyses of idealized shear structures, the accuracy of the transformation procedure is verified. A seismic performance upgrade design example is presented to demonstrate the usefulness of the proposed method for achieving design performance goals using supplemental damping devices. Copyright © 2012 John Wiley & Sons, Ltd.     

土层地震反应等效线性化方法综述

当前土层地震反应分析所用的主要方法是一维等效线性化波动方法。简单阐述了等效线性化方法的基本原理,总结了其发展历程和现状。根据其原理和多年的应用实践,指出了其优点和缺点。其优点主要是概念简单明确,计算量较小,便于工程应用。其缺点主要是该方法本身不能反应地震波在土体传播的真实过程,在工程实践中处理软弱土层和强震动输入时所表现出的一些不合理的地方。并对这些优缺点的机理进行了简要地分析。     

Inelastic seismic response of stiffening systems and development of demand spectrum: Application to MSSS bridges

A stiffening system is a system that increases its stiffness as it goes under large displacements. Such behavioural characteristic can result from constitutive behaviour or at the structural level often from closure of gaps between various components (sub‐systems) of the structure. An example of the latter situation is multi‐span simply supported (MSSS) bridges under horizontal earthquake ground motion. Unlike softening systems, stiffening systems have not been studied. In addition to the need for more understanding of the seismic response of stiffening systems, there is a need to develop response spectrum that can be used in design. Several parameters including gap size and ratios of sub‐systems stiffness, strength, and mass control the behaviour of a stiffening system. In this study, a simplified stiffening model is developed and over 367 000 cases are analysed to investigate the nonlinear stiffening behaviour and pounding. Parameters considered also include ground motion characteristic. Results are evaluated and compared in terms of displacement and dissipated hysteretic energy. Parameter study results show that, on average, the displacement response is lower for stiffening systems, however, they dissipates higher hysteretic energy, due to higher yield cycles and yield excursions, and can possibly sustain more damage than a bilinear, elastic–plastic system. Using parameter study database, design response spectrum for stiffening systems is also proposed and its practical application is demonstrated through its application to an MSSS bridge. Results of this study goes beyond MSSS bridges and will have application for many structural systems where response is characterized by a stiffening behaviour. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of structural characterizations on fragility functions of bridges subject to seismic shaking and lateral spreading

This paper evaluates the seismic vulnerability of different classes of typical bridges in California when subjected to seismic shaking or liquefaction-induced lateral spreading. The detailed structural configurations in terms of superstructure type, connection, continuity at support and foundation type, etc. render different damage resistant capability. Six classes of bridges are established based on their anticipated failure mechanisms under earthquake shaking. The numerical models that are capable of simulating the complex soil-structure interaction effects, nonlinear behavior of columns and connections are developed for each bridge class. The dynamic responses are obtained using nonlinear time history analyses for a suite of 250 earthquake motions with increasing intensity. An equivalent static analysis procedure is also implemented to evaluate the vulnerability of the bridges when subjected to liquefaction-induced lateral spreading. Fragility functions for each bridge class are derived and compared for both seismic shaking （based on nonlinear dynamic analyses） and lateral spreading （based on equivalent static analyses） for different performance states. The study finds that the fragility functions due to either ground shaking or lateral spreading show significant correlation with the structural characterizations, but differences emerge for ground shaking and lateral spreading conditions. Structural properties that will mostly affect the bridges＇ damage resistant capacity are also identified.     

Nonlinear FE model updating and reconstruction of the response of an instrumented seismic isolated bridge to the 2010 Maule Chile earthquake

Nonlinear finite element (FE) modeling has been widely used to investigate the effects of seismic isolation on the response of bridges to earthquakes. However, most FE models of seismic isolated bridges (SIB) have used seismic isolator models calibrated from component test data, while the prediction accuracy of nonlinear FE models of SIB is rarely addressed by using data recorded from instrumented bridges. In this paper, the accuracy of a state‐of‐the‐art FE model is studied through nonlinear FE model updating (FEMU) of an existing instrumented SIB, the Marga‐Marga Bridge located in Viña del Mar, Chile. The seismic isolator models are updated in 2 phases: component‐wise and system‐wise FEMU. The isolator model parameters obtained from 23 isolator component tests show large scatter, and poor goodness of fit of the FE‐predicted bridge response to the 2010 Mw 8.8 Maule, Chile Earthquake is obtained when most of those parameter sets are used for the isolator elements of the bridge model. In contrast, good agreement is obtained between the FE‐predicted and measured bridge response when the isolator model parameters are calibrated using the bridge response data recorded during the mega‐earthquake. Nonlinear FEMU is conducted by solving single‐ and multiobjective optimization problems using high‐throughput cloud computing. The updated FE model is then used to reconstruct response quantities not recorded during the earthquake, gaining more insight into the effects of seismic isolation on the response of the bridge during the strong earthquake.     

Bi‐directional coupled tuned mass dampers for the seismic response control of two‐way asymmetric‐plan buildings

This paper proposes bi‐directional coupled tuned mass dampers (BiCTMDs) for the seismic response control of two‐way asymmetric‐plan buildings subjected to bi‐directional ground motions. The proposed BiCTMD was developed from the three‐degree‐of‐freedom modal system, which represents the vibration mode of a two‐way asymmetric‐plan building. The performance of the proposed BiCTMD for the seismic response control of elastic two‐way asymmetric‐plan buildings was verified by investigating the reductions of the amplitudes of the associated frequency response functions. In addition, the investigation showed that the proposed BiCTMD is effective in reducing the seismic damage of inelastic asymmetric‐plan buildings. Therefore, the BiCTMD is an effective approach for the seismic response control of both elastic and inelastic two‐way asymmetric‐plan buildings. Copyright © 2010 John Wiley & Sons, Ltd.