Loading rate effects of high damping seismic isolation rubber bearing on earthquake responses

This paper investigates the effects of the loading rates of high damping seismic isolation rubber bearing on earthquake responses. For this purpose, a seismically isolated system is formulated by the Runge-Kutta numerical algorithm with nonlinear rate model of high damping rubber bearing to carry out the seismic time history response analysis. Results, of the seismic time history response analyses using both the present parameter equations and Fujita's equations are compared with those of pseudo dynamic tests. From these results it is confirmed that the parameter equations of high damping rubber bearing should be obtained by tests with the loading rate equivalent to the isolation frequency as close as possible.     

大型岸边起重机的地震振动台试验研究

设计了集装箱码头岸边装卸起重机（简称岸桥）的1∶50缩比模型及其隔震装置;利用锤击模态试验和地震振动台试验获取了1∶50缩比模型在有无隔震装置下的动态特性和地震响应。试验结果表明：岸桥自身结构具有相对较大的地震抵抗力和整体稳定性,能够满足抗震设计的要求;隔震装置开启后,各测点应变响应的幅值及加速度响应的幅值均有明显的减小,这说明岸桥所采用的隔震装置设计合理有效,且减震效果明显。     

多维地震作用下砖石古塔动力反应耦联分析

古塔砌体抗拉强度低,在地震作用下结构极易开裂,引起刚度沿横截面分布不均匀,结构平面刚度中心偏离质量中心而发生运动耦联。为研究多维地震作用下古塔动力反应的耦联关系,依据兴教寺玄奘塔结构模型振动台试验结果,对比分析了古塔结构在双向及三向地震作用下加速度及位移反应的耦联效应随高度的变化规律,参照结构破坏现象针对地震反应耦联机制进行分析。结果表明:在多维地震作用下古塔结构开裂破坏后,平面刚度发生变化,引起动力反应耦联;结构加速度及位移反应耦联效应系数随着测点高度的变化规律基本一致,但沿不同方向动力反应的耦联特征略有变化,多数加载工况下动力反应耦联系数的最大值为1.2左右。研究结果可为砖石古塔地震反应分析结果修正提供参考。     

Seismic analysis and parametric study of SDOF lead-rubber bearing (LRB) isolation systems with recentering shape memory alloy (SMA) bending bars

Base isolation has been considered one of aseismic design methodologies based on belief that it is feasible to separate the superstructure from the supporting ground, thereby preserving structural members and their internal contents from damage caused by earthquake motions. Although remarkable progress was achieved in this isolation technique towards the end of the century, a number of catastrophic building failures are still found where earthquake with severe ground motion attacked. In particular, high-rise buildings that have been currently constructed in urban area are very vulnerable when exposed to such impulsive events, and thus large relative displacement occurs at the isolator interface. The obstacles in or in the vicinity of the isolator interface destroy seismic performance. In this study, the innovative isolation systems incorporated with superelastic Shape memory alloy (SMA) bars functioning as seismic restrainers are suggested in order to more effectively maintain structural integrity. The superelastic SMA bending bars supply recentering force to the base isolator that accordingly makes a significant contribution to reducing permanent deformation over entire structure. The base Lead-rubber bearing (LRB) isolators with superelastic SMA bars are considered as inelastic behavior reproduced by component spring elements. The response of the proposed base isolators are compared with those of the conventional LRB isolators. Through the observation of the analysis results, it can be concluded that recentering LRB isolators create the improvement of seismic performance in terms of strength, energy dissipation and recentering effect.     

An experimental study on LMR core seismic behavior with fluid couplings between closely spaced hexagons

In LMR (Liquid Metal Reactor) core seismic behavior, the fluid coupling between closely spaced hexagons is known to have a very strong effect on the natural frequencies and the seismic responses. In this paper, an experimental study is carried out to investigate the fluid coupling effects with reduced scale mock-ups with three types of hexagonal duct systems and three types of input seismic motions such as the ElCentro 1940 time history, the artificial time history (Reg. 1.60), and the Kobe time history by using a one-dimensional shaking table facility. The results of the experimental studies are compared and discussed with those of the analyses performed by using the SAC-CORE code, which implements a numerical algorithm of the CFAM (Consistent Fluid Added Mass) matrix proposed in a previous paper. From the results, it is found that the fluid coupling between closely spaced hexagons becomes stronger with an increasing number of the neighboring hexagonal ducts, and this causes the natural frequency to be significantly changed and it affects the seismic time history responses too.     

边坡条件对重力式挡墙地震位移模式的影响

基于大型振动台模型试验,研究边坡条件对重力式挡墙地震位移模式及其变化方式的影响。振动台模型试验采用2个比尺1∶8的基覆边坡和顺层边坡模型,支挡结构为重力式挡墙与格构式锚杆框架二级组合式结构,地震波选用大瑞人工波和Kobe波。研究表明,基覆边坡中重力式挡墙地震位移模式主要有4类,即绕墙趾向边坡外侧转动、以滑动为主的向边坡外侧滑动与绕墙趾向边坡外侧转动的耦合、以转动为主的绕墙趾向边坡外侧转动与向边坡外侧滑动的耦合以及以滑动为主的向边坡外侧滑动与绕墙踵向边坡方向转动的耦合。顺层边坡中重力式挡墙地震位移模式主要有2类:绕墙趾向边坡外侧转动,绕墙趾向边坡外侧转动与离开边坡土体向外侧滑动的耦合。当地震烈度大于VII度时,重力式挡墙才产生动位移模式。边坡条件、地震波类型及烈度对重力式挡墙地震位移模式及其变化方式的影响较大,对相对位移的影响较小。     

基于谱分析的30m望远镜三镜支撑结构地震分析

为了满足30 m望远镜 （TMT）三镜系统（M3S）对抗震性能的要求,对在返回周期为200年和1000年的地震载荷条件下的三镜支撑结构的性能进行了分析。首先,根据三镜支撑结构的特点,对TMT整体的地震响应谱进行了修正,得到了适用于三镜支撑结构的地震响应谱。然后,分析了三镜支撑结构在不同等级地震激励下的位移、应力和加速度响应。分析结果显示,当返回周期为1000年的地震从水平面内两个正交方向及竖直方向同时传递到三镜支撑结构中时,系统响应最大;此时,三镜支撑结构中各部件的最大加速度为2.844g,最大位移为1.544 mm,最大应力为552.316 MPa,三镜上最大应力为1.401 MPa。根据材料力学性能可知,侧支撑杆会发生破坏,需要采取地震防护措施对三镜进行保护。本文在进行谱分析时较完整地考虑了各项因素,结果数据精确可靠,可为三镜系统的详细设计提供指导。     

模拟地震振动台模型试验相关问题探究

为了更好地服务工程抗震研究,以同济大学多功能振动台试验室为例,探讨在试验室视角下模拟地震振动台模型试验相关问题及解决方法.通过对试验模型设计、安装、加载等试验室参与的各环节进行分析与研究,提出一些建议,为建筑结构抗震试验提供参考.     

液压限位隔离系统的抗冲击性能研究

在舰载隔离系统中安装限位器可有效限制设备的最大相对位移,但传统橡胶限位器易对系统产生严重的二次冲击。首先,建立了液压限位器的数学模型,并通过杜哈梅积分法对隔离系统的冲击响应特性进行了仿真分析;然后,设计了带液压限位器的隔离系统试验装置并进行了冲击测试试验,比较了不同限位器参数对抗冲击效果的影响;最后,对比分析了液压限位与橡胶限位隔离系统的冲击响应特性,与无限位的隔离系统相比,液压限位可减小近60%的最大相对位移响应,存在一个最佳节流孔孔径,可使系统获得最佳隔振效果。研究结果表明：与传统橡胶限位隔离系统相比,在相对位移响应近似相等的条件下,加速度响应可降低44.5%,大幅提高舰载设备的抗冲击性能。     

Identification of modal parameters of a time invariant linear system by continuous wavelet transformation

The applications of wavelet transforms have received significant attentions in many fields. This work proposes a procedure for identifying modal parameters of a linear system using the continuous wavelet transform. The merits of the proposed procedure over the exiting schemes of applying the wavelet transform to system identification for a linear system are in use of the time invariance property and filtering ability of the transform to enhance the efficiency of identifying the modal parameters of a structure from its earthquake responses or free vibration responses. The effectiveness and accuracy of the proposed procedure are validated via numerical simulations. The effects of noise and wavelet function on identifying the modal parameters of the structure are also explored in processing the numerically simulated acceleration responses of a six-story shear building subjected to base excitation. The dynamic characteristics of close modes are accurately determined. Finally, the proposed procedure is adopted to obtain the modal parameters of a three-story non-symmetric steel frame from its measured acceleration responses in a shaking table test. A total of nine modes are identified, including modes with high frequencies and very small amplitude.     

地基与密肋复合墙结构动力相互作用测试分析

为研究黄土地基与密肋复合墙结构相互作用对结构地震响应及破坏机制的影响规律,分别在考虑地基与结构相互作用及刚性地基条件下进行了1/15比例密肋复合墙结构振动台试验。按不同烈度输入单向水平、双向水平及三向加速度的EL-Centro波和天津波,测试了结构的加速度反应,比较了考虑相互作用与刚性地基条件下的水平加速度响应,对比了两种条件下的破坏现象,分析了地基对所输地震波的放大效应及相互作用对结构楼层动力响应的影响。结果表明:输入地震波后,相互作用体系的破坏形式为地基开裂,刚性地基条件下结构的破坏形式为底部拼接缝滑移;地基对地震作用的放大效应与地震波频谱特性、幅值及输入方式相关;相互作用对不同楼层水平动力响应的影响程度不同,也受到地震波频谱及烈度的影响;各工况条件下的相互作用效应与地基放大效应较为接近,可将地基对地震作用的放大系数作为考虑相互作用后的地震作用效应调整系数。     

运用模态综合法的车桥自激激励耦合振动分析

针对车桥耦合振动影响自动化码头集装箱小车-低架桥结构安全和使用效率的问题,基于双协调自由界面模态综合法求解了车桥系统在轨道不平顺和轮对蛇形运动自激激励下的耦合振动时域响应,轨道不平顺时程通过Shinozuka一元多维平稳随机过程模拟法从轨道谱生成。用量纲分析法推导了结构动力模型相似条件,设计了试验模型,结合模型试验分析了铅芯橡胶支座、小车速度对车桥耦合振动响应的影响。模型试验与原型仿真结果相互验证表明:模态综合求解车桥耦合振动响应的仿真方法合理;使用铅芯橡胶支座可有效减小车桥加速度响应和支柱反力;车桥加速度响应随着小车速度的增大而增大,系统横向共振临界车速低于竖向车速,临界车速可由简支梁在移动集中力作用下车桥共振条件来估算。     

基于〖WTHZ〗Copula函数的渡槽结构地震动易损性分析

在结构易损性分析中,由于构件之间的地震需求存在相关性,直接建立渡槽系统中基本构件的联合概率分布函数较为困难,为此引入二维Copula函数对构件地震需求之间的相关结构进行描述,简化联合分布函数的建模过程。首先,对某输水渡槽中的一跨进行时程分析,以地面峰值加速度为自变量,以排架的位移延性比和橡胶支座的变形大小为损伤指标,考虑地震动和结构参数的不确定性,建立排架、橡胶支座的易损性曲线;其次,通过Copula函数建立渡槽系统的易损性曲线;最后,通过1阶界限法得到渡槽系统易损性的上、下界。计算结果表明,基于Copula函数计算得到的失效概率均位于1阶界限法的上、下界之间。研究结果有助于简化渡槽系统易损性曲线的建模过程,为研究渡槽构件地震需求之间的相关性提供新思路和方法。     

液压振动台控制策略的研究

结合液压伺服控制理论和液压振动台试验理论,给出杭州亿恒公司为厦门大学土木工程系研制的液压振动台数学模型。针对该振动台提出了三参量伺服控制和闭环迭代控制相结合的控制策略,通过理论分析,三参量伺服控制能够调节液压系统的频宽和阻尼系数;闭环迭代控制能够实现较高地震波波形模拟精度。并通过试验验证了在振动台上使用该控制策略能够获得较好的控制效果。     

Experimental implementation of a building structure with a tuned liquid column damper based on the real-time hybrid testing method

In this study, the real-time hybrid test using a shaking table for the control performance evaluation of a U-shaped tuned liquid column damper (TLCD) controlling the response of earthquake-excited building structure is experimenttally implemented. In the test, the building structure is used as a numerical part, on which a U-shaped TLCD adopted as an experimental part was installed to reduce its response. At first, the force that is acting between a TLCD and building structure is measured from the load cell attached on shaking table and is fed-back to the computer to control the motion of shaking table. Then, the shaking table is driven such a manner that the error between the interface acceleration computed from the numerical building structure under the excitations of earthquake and the fed-back interface force and that measured from the shaking table. The control efficiency of the TLCD used in this paper is experimentally confirmed by implementing this process of shaking table experiment on real-time.     

基于WMRA的隔震结构时变非线性参数识别

基于小波多分辨率分析(wavelet multi-resolution analysis,简称WMRA)理论,建立结构时变非线性参数识别方法,研究隔震结构在地震作用下表现出来的时变非线性力学行为。首先,以描述隔震支座的迟滞非线性Boucwen模型为研究对象,引入3阶有效数值差分技术,将运动方程中非线性模型的恢复力增量进行线性化,形成递推观测方程;其次,基于WMRA理论,将观测方程中每一待识别参数采用小波多分辨率展开,将模型参数识别问题转化成多元线性回归模型中小波重构系数的估计问题;最后,分别采用数值模拟、串联隔震体系(serial seismic isolation system,简称SIS)振动台试验测试数据,识别结构及隔震层参数随时间的演化规律,验证该识别方法的正确性和适用性,为隔震结构在施工、运营期各阶段状态评估提供一定参考。     

基于自适应技术的结构参数与输入同步反演

发展一种基于遗传优化算法的自适应追踪技术,结合输入未知条件下的二次误差平方和方法,利用事件中的加速度响应数据实现结构参数与输入的同步反演,判断并追踪结构损伤,包括损伤发生的时间、位置和程度。三自由度迟滞非线性系统数值仿真结果表明,该方法能够精确有效地追踪结构参数的变化,并同步反演结构的未知输入。此外,对三自由度基础隔振结构模型进行了多工况实验研究。结果表明,所发展方法能够实时有效地追踪结构时变物理参数、反演结构未知基底激励,进而精准地获取结构的损伤信息。     

基于惯性半径相似岸桥模型的地震试验

岸桥结构进行缩尺模型设计时,各构件(梁)的几何尺寸可由原形的尺寸按相似比推导出来,梁截面厚度却不能和长度按同一比尺缩小,导致梁截面尺寸不能完全相似。笔者采用截面惯性半径相似的方法控制抗弯刚度设计梁截面尺寸。以该方法为参考制作了一台岸桥缩尺模型并进行地震试验,缩尺模型试验测量值与数值计算结果接近,结构各考察点加速度、应变出现极值的大小以及所对应的时间都比较接近。该缩尺模型能替代完全相似模型,所得试验值能近似反映实际结构在地震中的动态响应,验证了截面惯性半径相似模型设计方法的可行性,为工程中大型钢结构缩尺模型的设计及后续的地震试验研究提供了参考。     

电液振动台正弦振动自适应控制方法

电液振动台是大型结构正弦振动模拟实验的关键设备。受液压系统频宽及系统中存在的死区、摩擦力等因素影响,正弦振动实验中加速度输出信号存在跟踪精度低、波形失真度大等问题。为提高电液振动台控制精度,提出正弦振动自适应逆控制及谐波抑制复合控制策略。通过带遗忘因子的RLS算法构建自适应逆控制器,提高正弦波形的跟踪精度。基于快速块LMS算法构建双次自适应谐波抑制控制器,减小系统加速度输出信号波形失真度。最后通过振动台实验,验证了控制策略的有效性。     

环形起重设备的局部动力效应和抗震分析

对大型环形起重机设备进行抗震分析时,考虑了局部动力效应的影响及不同标高处系统加速度谱值的变化,推导了大型环形起重机设备在42.5 m标高处的地震作用及地震响应计算公式。编制了相应的计算程序,通过对实际设备的分析与计算,探讨了局部动力效应及加速度谱值变化的影响,这对工程设计具有一定的指导意义。