Performance of a base isolator with shape memory alloy bars

A new and innovative base isolation device is introduced in this paper based on extensive research carried out by the authors and their co-workers. A prototype of the device was built and experimentally tested on the shaking table. The new base isolation device consists of two disks, one vertical cylinder with an upper enlargement sustained by three horizontal cantilevers, and at least three inclined shape memory alloy (SMA) bars. The role of the SMA bars is to limit the relative motion between the base and the superstructure, to dissipate energy by their super-elastic constitutive law and to guarantee the re-centring of the device. To verify the expected performance, a prototype was built and tested under sinusoidal waves of displacement of increasing frequency with different amplitudes. It is shown that the main feature of the proposed base isolation device is that for cyclic loading, the super-elastic behavior of the alloy results in wide load-displacement loops, where a large amount of energy is dissipated.     

Vertical vibration isolator having piecewise‐constant restoring force

We present a vertical vibration isolator having a piecewise‐constant restoring force, which belongs to a class of passive and nonlinear vibration isolators. In vertical vibration isolation, direct use of low‐stiffness elements leads to unacceptably large deformations due to self‐weight. To overcome the difficulty, we apply a combination of constant‐force springs, each of which sustains a constant load regardless of its stretch. By arranging the constant‐force springs, so that the isolator has a piecewise‐constant restoring force, we alleviate the problem of the excessive deformation caused by self‐weight, provide stability at the static equilibrium state along with the self‐centering capability, and realize a large stroke while keeping the mechanism simple and compact. Further, we attempt to limit the response acceleration within a tolerance regardless of the frequency spectrum and the magnitude of earthquake ground motions. We demonstrate the effectiveness of the present isolator through shaking table tests and numerical simulations. Copyright © 2009 John Wiley & Sons, Ltd.     

三维隔震(振)支座的工程应用与现场测试

首先介绍了一种新型三维隔震(振)支座,该支座由联接件、竖向隔振支座和水平隔震支座组成。竖向隔振支座和水平隔震支座具有较小刚度,采用该类型支座的隔震结构,其竖向基频和水平基频可远离地铁、铁路振动和地震的主频,从而实现竖向隔振和水平隔震作用。其次介绍了该三维隔震(振)支座在某一地铁平台上部结构中的应用情况,对该类型支座进行了竖向性能和水平性能试验。最后对三维隔震(振)结构与传统结构进行了地铁运行时结构振动的对比测试。测试结果表明:三维隔震(振)系统对振动的高频信号具有显著衰减效果。     

Theory and experimental study for sliding isolators with variable curvature

Because a conventional isolation system with constant isolation frequency is usually a long‐period dynamic system, its seismic response is likely to be amplified in earthquakes with strong long‐period wave components, such as near‐fault ground motions. Seismic isolators with variable mechanical properties may provide a promising solution to alleviate this problem. To this end, in this work sliding isolators with variable curvature (SIVC) were studied experimentally. An SIVC isolator is similar to a friction pendulum system (FPS) isolator, except that its sliding surface has variable curvature rather being spherical. As a result, the SIVC's isolation stiffness that is proportional to the curvature becomes a function of the isolator displacement. By appropriately designing the geometry of the sliding surface, the SIVC is able to possess favorable hysteretic behavior. In order to prove the applicability of the SIVC concept, several prototype SIVC isolators, whose sliding surfaces are defined by a sixth‐order polynomial function, were fabricated and tested in this study. A cyclic element test on the prototype SIVC isolators and a shaking table test on an SIVC isolated steel frame were all conducted. The results of both tests have verified that the prototype SIVC isolators do indeed have the hysteretic property of variable stiffness as prescribed by the derived formulas in this study. Moreover, it is also demonstrated that the proposed SIVC is able to effectively reduce the isolator drift in a near‐fault earthquake with strong long‐period components, as compared with that of an FPS system with the same friction coefficient. Copyright © 2011 John Wiley & Sons, Ltd.     

Full‐scale shaking table test of a base‐isolated medical facility subjected to vertical motions

Base isolation is a well known technology that has been proven to reduce structural response to horizontal ground accelerations. However, vertical response still remains a topic of concern for base‐isolated buildings, perhaps more so than in fixed‐base buildings as isolation is often used when high performance is required. To investigate the effects of vertical response on building contents and nonstructural components, a series of full‐scale shaking table tests were conducted at the E‐Defense facility in Japan. A four‐story base‐isolated reinforced concrete building was outfitted as a medical facility with a wide variety of contents, and the behavior of the contents was observed. The rubber base isolation system was found to significantly amplify vertical accelerations in some cases. However, the damage caused by the vertical ground motions was not detrimental when peak vertical floor accelerations remained below 2 g with three exceptions: (1) small items placed on shelves slid or toppled; (2) objects jumped when placed on nonrigid furniture, which tended to increase the response; and (3) equipment with vertical eccentricities rocked and jumped. In these tests, all equipment and nonstructural components remained functional after shaking. Copyright © 2013 John Wiley & Sons, Ltd.     

Theoretical and experimental research on a new system of semi-active structural control with variable stiffness and damping

In this paper, a new system of semi active structural control with active variable stiffness and damping (AVSD) is suggested. This new system amplifies the structural displacement to dissipate more energy, and in turn, effectively reduces the structural response in the case of relatively small story drifts, which occur during earthquakes. A predictive instantaneous optimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table tests of a 1/4 scale single story structural model with a full scale control device have been conducted. From the experimental and analytical results, it is shown that when compared to structures without control or with the active variable stiffness control alone, the suggested system exhibits higher efficiency in controlling the structural response, requires less energy input, operates with higher reliability, and can be manufactured at a lower cost and used in a wider range of engineering applications.     

SMA阻尼器偏心结构平-扭震动控制试验研究

为了验证提出的新型筒式自复位形状记忆合金阻尼器(telescopic recentering shape memory al-loy damper,TRSMAD)对结构平动-扭转耦联振动反应的抑制作用,进行了偏心结构消能减震体系的振动台试验。设计了一个1/4缩尺的三层两跨单向偏心的钢框架模型,将提出的新型SMA阻尼器安装在结构底层的一侧,通过振动台分别对无控条件下和装有阻尼器的有控条件下的结构反应进行了研究。试验结果表明:(1)在各地震波作用下,TRSMAD对结构的平动反应有很好控制效果,而对结构各层扭转角位移的控制效果稍低;(2)不同地震波下的控制效果有所不同:对结构的平动位移而言,天津波的减震率最高,El Centro波次之,最后为Taft波;对结构扭转角的控制,平均而言,除了天津波作用下第二层为特例外,对El Centro波的减震效果最好,其次为Taft波,最后为天津波;(3)同一地震波下,阻尼器对结构模型一层的位移控制效果较其他层为优。     

柱承式立筒群仓结构模型振动台试验研究

为研究不同贮料状态下钢筋混凝土柱承式立筒群仓结构的动力特性及其在地震作用下的动力响应规律,对缩尺比例为1:25的3×3组合柱承式立筒群仓结构模型进行了振动台试验。试验结果表明:柱承式筒仓结构具有"上刚下柔"的特性,使其加速度响应和整体变形均沿高度呈折线型,折点在刚度突变的柱顶和仓壁连接部位;贮料状态对立筒群仓结构动力特性的影响较大,随着贮料质量的增加,群仓模型加速度响应、位移响应的弯折效应均更加明显,边仓和角仓的加速度响应均逐渐增大;贮料及其与仓体间相互作用对耗能的贡献随着台面加载等级的增加而逐渐加大。     

带竖向构造钢筋再生混凝土砖结构振动台试验研究

提出了带竖向构造钢筋再生混凝土砖砌体结构,进行了2个两层再生混凝土砖砌体房屋结构1/2缩尺模型的模拟地震振动台试验研究,2个结构模型的墙体厚度均为120 mm,一层设有门洞和窗洞,二层设有窗洞。2个模型中,1个为带竖向构造钢筋再生混凝土砖砌体房屋,1个为普通无竖向构造钢筋再生混凝土砖砌体房屋。试验中输入El Centro地震动,测试分析了台面加速度反应、一层和二层顶板加速度反应、结构层间位移反应以及各阶段结构损伤与破坏特征等。研究表明:带竖向构造钢筋再生混凝土砖砌体房屋比普通再生混凝土砖砌体房屋的破坏程度轻,墙体裂缝位置相对错动小,抗震性能显著提高;带竖向构造钢筋再生混凝土砖砌体房屋可用于地震区村镇建筑。     

主动变刚度-阻尼系统预测最优控制的理论与试验研究

介绍了一种具有自主知识产权的新型开关控制型半主动控制系统——主动变刚度.阻尼(AVS.D)系统的减振控制机理,建立了AVS.D结构振动控制体系的运动方程。为了合理补偿AVS.D系统实时控制过程中不可避免地存在着的控制时滞,本文提出一种预测最优控制算法,推导了其开关控制律。为了检验AVS.D系统的减震控制效果及预测最优控制算法的有效性,我们设计研制出AVS.D装置,编制了AVS.D系统预测最优控制的实时控制软件,在某单层钢框架模型上进行了AVS.D系统的模拟地震振动台试验,比较了不同控制方式时的减震效果。研究结果表明,本文所提出的预测最优控制算法是非常有效的,可推广应用于所有开关控制型半主动控制系统。AVS.D系统具有反应放大功能,经济可靠、安全有效,可望有较好的工程应用前景。     

考虑土与结构相互作用效应的结构减震控制大型振动台模型试验研究

本文设计并完成了考虑土与结构相互作用的结构减震控制大型振动台模型试验。通过对四种结构形式的对比试验，探讨了土与结构相互作用（ＳＳＩ）效应对结构地震反应的影响以及调谐质量阻尼器（ＴＭＤ）在刚性和柔性地基条件下对主体结构的减震效应。通过比较同一地震动作用下主体结构在刚性和柔性两种地基条件下的地震反应，可知：ＳＳＩ效应具有降低和提高结构减震控制效果的双重作用，其综合效果与输入地震动的频谱特性、加速度峰值大小有关。由于ＳＳＩ效应在结构地震反应中发挥着双重的作用，因而使得基于刚性地基假定下设计的ＴＭＤ减震控制系统在柔性地基条件下的控制效果不太理想，甚至会出现负面效应。本文还探讨了在柔性地基条件下影响结构减震控制效果的一些因素。     

Optimum design and experimental study of multiple tuned mass dampers with limited stroke

This paper develops a two‐stage optimum design procedure for multiple tuned mass dampers (MTMD) to reduce structural dynamic responses with the limitation of MTMD's stroke. A new performance index, which is a linear combination of structural response ratio and MTMD stroke ratio by a weighting factor α, is proposed; α is in the range from 0 to 1.0. The larger the α, the more important the stroke. The case of α=1.0 indicates that MTMD is locked. The analytical results show that the MTMD's stroke can be significantly suppressed with little sacrifice of structural control effectiveness when an appropriate α is selected. To verify the design algorithm, a 360 kg‐MTMD composed of five TMD units arranged in parallel was fabricated. Shaking table tests of a large‐scale three‐story building with and without the MTMD under earthquake excitations were conducted at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The experimental results show that MTMD is not only effective in mitigating the building responses but also is successful in suppressing its stroke. Copyright © 2010 John Wiley & Sons, Ltd.     

含软弱夹层岩质边坡的模态分析及其对边坡地震动力响应影响的初步研究

本文以含软弱夹层岩质边坡作为研究对象,基于数值软件ANSYS的模态分析给出了含不同倾角与厚度软弱夹层边坡的前5阶固有频率与振型,并分析了夹层倾角和厚度对边坡固有模态的影响。接着,结合已有的大型振动台模型试验结果,在小应变范围内讨论了边坡的固有模态与其动力响应特性之间的关系。结果表明:(1)在夹层倾角相同时,含较厚软弱夹层边坡固有频率低于含较薄软弱夹层边坡;(2)在夹层厚度相同时,随着倾角增加,夹层从反倾变化到顺倾,低阶(1、2)固有频率也逐渐增加,而高阶(3、4、5)固有频率则呈下降趋势;(3)从第3、4阶开始,边坡变形受夹层影响增强;(4)基于加速度傅里叶谱比分析得出的边坡响应放大频率与边坡前5阶固有频率范围接近,加速度和位移响应在夹层及以上部位响应强烈,与边坡前5阶振型较为一致,预示了边坡的共振响应。需要指出的是,本文得出的结论尚且不能用于准确解释边坡在大变形及破坏阶段的动力响应特征,但可为边坡动力特性及共振响应的深入研究提供思路。     

复杂退台高位转换高层建筑振动台试验与分析

对一幢具有转换层的复杂退台式框架剪力墙高层建筑的1/35缩尺模型进行了模拟地震振动台试验,深入研究该结构的动力特性和地震反应特征.试验及理论分析表明:该结构的抗震性能基本满足现行规范要求;由于结构上部逐渐退台,因而结构顶部有较明显的鞭端效应;结构首层和结构转换层及其相邻层的剪力墙、转换层上下层柱是受力较大的区域,应当局...     

Computational simulation of slab vibration and horizontal‐vertical coupling in a full‐scale test bed subjected to 3D shaking at E‐Defense

This paper focuses on slab vibration and a horizontal‐vertical coupling effect observed in a full‐scale 5‐story moment frame test bed building in 2 configurations: isolated with a hybrid combination of lead‐rubber bearings and cross‐linear (rolling) bearings, and fixed at the base. Median peak slab vibrations were amplified—relative to the peak vertical shake table accelerations—by factors ranging from 2 at the second floor to 7 at the roof, and horizontal floor accelerations were significantly amplified during 3D (combined horizontal and vertical) motions compared with 2D (horizontal only) motions of comparable input intensity. The experimentally observed slab accelerations and the horizontal‐vertical coupling effect were simulated through a 3D model of the specimen using standard software and modeling assumptions. The floor system was modeled with frame elements for beams/girders and shell elements for floor slabs; the insertion point method with end joint offsets was used to represent the floor system composite behavior, and floor mass was finely distributed through element discretization. The coupling behavior was partially attributed to the asymmetry of the building that was intensified by asymmetrically configured supplemental mass at the roof. Horizontal‐vertical coupled modes were identified through modal analysis and verified with evaluation of floor spectral peaks.     

Hybrid vibration experiments with a bridge foundation system model

In order to improve seismic design technology of bridges, it is necessary to evaluate the vibration characteristics of a bridge–soil system that consists of soil, foundation structure, pier and superstructure. However, there have been few experimental studies on seismic behavior of bridge–soil system. In this paper, we conducted the hybrid vibration experiment on seismic behavior of bridge–soil system, and examined the applicability of hybrid vibration experiment to study seismic response of bridge–soil system. Based on the experiment results, seismic response of bridge was quantitatively studied.     

薄弱层设置耗能阻尼器支撑的钢框架模型振动台试验

设计制作了一个五层钢框架模型,在其第一层、第三层和第五层薄弱层分别设置摩擦阻尼器、粘弹性阻尼器和粘弹性-摩擦阻尼器等三种耗能阻尼器支撑,进行了罕遇地震和多遇地震下的振动台试验。试验结果表明,耗能阻尼器支撑能够有效地控制结构的地震反应。     

Test and numerical simulation of a new type of hybrid control technique

In this paper, a new hybrid control technique, based on a combination of base-isolation and semi-active variable stiffness/damping in a superstructure, is presented. To illustrate the efficiency of the proposed control system, model tests on a mini-electromagnetic shaking table and a numerical simulation were performed. The test and numerical calculation results indicate that this new hybrid control mode with additional damping and smaller additional stiffness can achieve a better control efficiency.     

Effects of balanced impact damper in structures subjected to walking and vertical seismic excitations

This study investigates whether a balanced impact damper (BID) with a vertically suspended impact body colliding with shock absorbing rubber can suppress vibrations of a floor slab subjected to walking and vertical seismic excitations. The impact body is suspended by coil springs to sustain its deadweight and centralize it within the gap, and collides with the stopper when its amplitude exceeds the specified gap width. The stopper is covered by a shock‐absorbing rubber made of polyurethane gel. The installed BID was evaluated in a single degree‐of‐freedom model of a floor slab subjected to vertical excitations. Simulations revealed that the installed BID properly controls the vibrations. Next, the effects of the BID installed on a steel plate were investigated in shaking table tests. The BID effectively suppressed vertical vibrations of the plate subjected to sinusoidal waves, seismic motions, and walking excitations. In addition, the shaking table tests were accurately simulated by the developed mathematical model of the damper. Copyright © 2015 John Wiley & Sons, Ltd.     

一种新型混合控制技术的振动台模型试验研究

本文提出了基底隔震和上部结构变刚度／阻尼半主动控制结合的一种新型混合控制型式,并且通过小型电磁振动台模型试验来研究其控制效能,为其今后更进一步理论和实验研究奠定基础。