Optimal PD/PID control of smart base isolated buildings equipped with piezoelectric friction dampers

Long-period pulses in near-field earthquakes lead to large displacements in the base of isolated structures.To dissipate energy in isolated structures using semi-active control,piezoelectric friction dampers（PFD） can be employed.The performance of a PFD is highly dependent on the strategy applied to adjust its contact force.In this paper,the seismic control of a benchmark isolated building equipped with PFD using PD/PID controllers is developed.Using genetic algorithms,these controllers are optimized to create a balance between the performance and robustness of the closed-loop structural system.One advantage of this technique is that the controller forces can easily be estimated.In addition,the structure is equipped with only a single sensor at the base floor to measure the base displacement.Considering seven pairs of earthquakes and nine performance indices,the performance of the closed-loop system is evaluated.Then,the results are compared with those given by two well-known methods：the maximum possive operation of piezoelectric friction dampers and LQG controllers.The simulation results show that the proposed controllers perform better than the others in terms of simultaneous reduction of floor acceleration and maximum displacement of the isolator.Moreover,they are able to reduce the displacement of the isolator systems for different earthquakes without losing the advantages of isolation.

Reduction of structural response to near fault earthquakes by seismic isolation columns and variable friction dampers

This paper focuses on the investigation of a hybrid seismic isolation system with passive variable friction dampers for protection of structures against near fault earthquakes. The seismic isolation can be implemented by replacing the conventional columns fixed to the foundations by seismic isolating ones. These columns allow horizontal displacement between the superstructure and the foundations and decouple the building from the damaging earthquake motion. As a result, the forces in the structural elements decrease and damage that may be caused to the building by the earthquake significantly decreases. However, this positive effect is achieved on account of displacements occurring in the isolating columns. These displacements become very large when the structure is subjected to a strong earthquake. In this case, impact may occur between the parts of the isolating column yielding their damage or collapse. In order to limit the displacements in the isolating columns, it is proposed to add variable friction dampers. A method for selecting the dampers＇ properties is proposed. It is carried out using an artificial ground motion record and optimal active control algorithm. Numerical simulation of a sevenstory structure shows that the proposed method allows efficient reduction in structural response and limits the displacements at the seismic isolating columns.

An Experimental and Analytical Study on Cross-Laminated Bamboo Rocking Walls with Friction Dampers

Cross-laminated bamboo(CLB)have a high strength to weight ratio and stable bidirectional mechanical properties.Inspired by the investigation on cross-laminated timber(CLT)rocking walls,CLB rocking walls with conventional friction dampers(CFDs)are studied in this paper.To investigate the mechanical properties of the CLB rocking wall,seven tests are conducted under a cyclic loading scheme,and different test parameters,including the existence of the CFDs,the moment ratio,and the loading times,are discussed.The test results show a bilinear behavior of the CLB rocking wall.The small residual displacements of the CLB rocking wall demonstrate an idealized self-centering capacity.The cumulative energy dissipation curves indicate that the energy dissipation capacity of the CLB rocking wall can be greatly improved with CFDs.The limit states of the CLB rocking wall under a lateral force are proposed based on the strains,stress,and damage level of the CLB material and posttensioned rebar.In addition,an analytical model of the CLB rocking wall is developed based on the proposed limit states of the CLB rocking wall to evaluate the hysteretic response of the CLB rocking wall,and the model is validated by the experimental data.The comparison results show the potential value of the analytical model for engineering design.

Improved suboptimal Bang-Bang control of aseismic buildings with variable friction dampers

One of the challenges in civil engineering is to find an innovative means of suppressing the structural vibration due to earthquake and wind loadings. This paper presents an approach for effectively suppressing vibrations of a structure with variable friction damper using a new Bang-Bang control input. A continuous function of story velocities is used to represent the improved control to reduce chatter, high frequency switching and avoid instability. With a genetic algorithm, the amplitudes of control and preloading friction forces individually prescribed in the controller and damper are optimized for enhancing the seismic performance of buildings. The control strategy for the friction damper is proposed for a three story building with one variable friction damper installed at the first story for seismic reduction. The numerical results indicate that a better reduction of peak response accelerations of floors can be achieved than those of the unmodified controller, and the adaptability of the control system is also improved greatly by comparison with the reduction ratios of the structural response energy excited by different earthquake intensities.

Analytical Method Determining Resonant Response of Blade with Dry Friction Damper

This paper presents an analytical method for determining the steady state response of blade with dry friction damper. A complete vibration cycle is divided into four successive intervals. The system possesses linear vibration characteristic during each of these intervals, which can be determined by using analytical solution forms. An analytical solution of the system periodic motion can be formed by combining the four intervals’ solutions. Numerical simulation shows that there are two response peaks in passage through the resonant frequencies of the system without the friction damper and with the friction damper fully stuck respectively. The amplitude of the first peak can be reduced up to 90% by adjusting the value of normal pressure force between the damper’s contacting surfaces. Whereas to determine the optimum pressure force, reduction of amplitudes of two peaks should be considered together.

Dynamics Modeling and Numerical Analysis of Rotor with Elastic Support/Dry Friction Dampers

The elastic support/dry friction damper is a type of damper which is used for active vibration control in a rotor system.To establish the analytical model of this type of damper,a two-dimensional friction model-ball/plate model was proposed.By using this ball/plate model,a dynamics model of rotor with elastic support/dry friction dampers was established and experimentally verified.Moreover,the damping performance of the elastic support/dry friction damper was studied numerically with respect to some variable parameters.The numerical study shows that the damping performance of the elastic support/dry friction damper is closely related to the stiffness distribution of the rotor-support system,the damper location,the pressing force between the moving and stationary disk,the friction coefficient,the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk.In general,the damper should be located on an elastic support which has a large vibration amplitude in order to achieve a better damping performance,and the more vibration energy in this elastic support concentrates,the better performance of the damper will be.The larger the tangential contact stiffness of the contact interface,and the stiffness of the stationary disk are,the better performance of the damper will be.There will be an optimal value of the friction force at which the damper performs best.

Retrofit of Ressalat jacket platform (Persian Gulf) using friction damper device

A friction damper device (FDD) is used for vibration control of an existing steel jacket platform under seismic excitation. First, the damping is presented for vibration mitigation of structures located in seismically active zones. A new method for quick design of friction or yielding damping devices is presented. The effectiveness of the damping system employing such FDDs in a jacket platform is evaluated numerically. The influence of key parameters of the damping system on the vibration suppression of the offshore structure is studied in detail. To examine the vibration control effectiveness of the FDD for the jacket platform, performance of the controlled structure under the seismic forces is studied using numerical simulations. A parametric study is undertaken to discover the optimized slip load and brace area of the FDD. It is shown that the FDD is effective in mitigating the dynamic responses of the offshore platform structure.

A new type of damper with friction-variable characteristics

Professor T. T. Soong is one of the early pioneers in field of earthquake responsc control of structures. A new type of smart damper, which is based on an Energy Dissipating Restraint （EDR）, is presented in this paper. The EDR by Nims and Kelly, which has a triangle hysteretic loop, behaves like an active variable stiffness system （AVS） and possesses the basic characteristics of a linear viscous damper but has difficulty in capturing the output and large stroke simultaneously needed for practical applicataions in engineering structures. In order to overcome this limitation, the friction surface in the original Sumitomo EDR is divided into two parts with low and high friction coefficients in this paper. The results of finite element analysis studies show that the new type of smart friction damper enables large friction force in proportion to relative displacement between two ends of the damper and has a large allowable displacement to fit the demands of engineering applications. However, unlike the EDR by Nims and Kelly, this type of friction variable damper cannot self re-center. However, the lateral stiffness can be used to restore the structure. The nonlinear time history analysis of earthquake response for a structure equipped with the proposed friction variable dampers was carried out using the IDARC computer program. The results indicate that the proposed damper can successfully reduce the earthquake response of a structure.

大跨度索穹顶结构半主动振动控制分析

为了实现大跨空间结构半主动振动控制,提出了一种基于模糊控制算法的半主动振动控制方法.以某体育馆大跨度索穹顶屋盖为分析对象,建立了基于台站与地震信息的地震动记录选择集,采用研发的新型压电摩擦阻尼器,开展索穹顶结构被动控制研究.将地面加速度和结构变形量2个指标作为控制参数,进行索穹顶结构半主动振动控制分析.结果表明:被动控制时不同地震动强度下结构峰值加速度、最大相对变形量的最小减振率平均值仅分别为3.7%和-1.6%;半主动控制下的压电摩擦阻尼器能够适应不同强度地震动,有效降低结构的峰值加速度和峰值位移,且峰值加速度减振率平均值为20.0%~41.9%,最大相对变形量减振率平均值为12.0%~19.0%.

摩擦阻尼器组合支座的隔震优化对比

为解决一种摩擦阻尼器组合隔震支座的有效性及计算方法的问题,研究了用于结构设计有限元建模的组合元件计算模型,包括水平向、竖向刚度和滞回模型。使用有限元软件SAP2000,对比研究了布置有该组合支座的优化隔震方案和传统橡胶支座的隔震优化方案在高宽比不同的高层框架剪力墙筒体结构的抗震性能。结果表明:与传统隔震支座方案相比,组合隔震支座隔震方案可适当延长结构自振周期,减小隔震层侧移,有效降低支座拉应力,提高支座的抗倾覆能力和支座耗能,还可有效降低上部结构的层间剪力及侧移等地震响应,证明组合隔震支座方案较传统隔震支座方案综合性收效明显。

四主缆大跨悬索桥抗震性能分析及减震措施优化

以燕矶长江大桥为工程背景,首先,采用动力非线性时程法分析了燕矶长江大桥抗震性能,并研究了设置电涡流-摩擦组合型阻尼器和黏滞阻尼器对大跨悬索桥抗震性能的影响;然后,对附加电涡流-摩擦组合型阻尼器摩擦力、阻尼系数和阻尼指数开展了参数敏感性分析;最后,从耗能角度分析地震作用下电涡流-摩擦组合型阻尼器减震特点.结果表明:在E2地震作用下,桥塔关键截面抗弯能力均大于弯矩需求;在“纵向+竖向”地震作用下梁端纵向位移较大.设置塔梁处纵桥向阻尼器后,可有效降低主桥梁端纵向位移;增大摩擦力、阻尼系数与降低阻尼指数均可提升梁端纵向地震响应的控制效果,但参数变化对桥塔控制截面的地震响应影响较小.阻尼系数较大时,电涡流阻尼主导了电涡流-摩擦组合型阻尼器耗能,相较于黏滞阻尼器,电涡流-摩擦组合型阻尼器对梁端纵向位移控制效果更好.

基于压电纤维复合材料半主动干摩擦阻尼器的设计与实验研究

针对薄壁结构的振动问题,设计了一种铺设压电纤维复合材料(Macro-Fiber Composite,MFC)的波纹形柔性干摩擦阻尼器。介绍了波纹形半主动干摩擦阻尼器的结构形式和驱动原理。通过准静态试验探究了阻尼器在不同电压序列下输入电压与输出正压力的关系,揭示了MFC驱动变形的迟滞非线性,并据此提出了局部线性化的驱动方案,规避了迟滞非线性给正压力控制带来的挑战。在此基础上,对安装上述阻尼器的悬臂梁结构开展了振动试验。结果表明,在设计工况下该阻尼器的减振效果良好,质量占比仅为5%的阻尼器即可使振动峰值下降79%;该半主动干摩擦阻尼器显著拓宽了有效工作范围,当振动水平为设计工况的9倍时,通过MFC驱动调控正压力,减振比例仍可保持在约75%,避免了阻尼效果的大幅衰减。

自复位转动摩擦阻尼器弯矩-转角恢复力性能研究

为了满足减震结构对可恢复功能的要求,针对传统摩擦阻尼器不具备自复位能力震后存在较大残余变形的问题,提出了一种基于形状记忆合金的自复位转动摩擦阻尼器,由摩擦耗能装置和形状记忆合金自复位装置组合而成。介绍了该SCRF(self-centering rotating friction)阻尼器的构造形式、工作原理,通过理论推导建立了SCRF阻尼器的弯矩-转角恢复力模型,通过ABAQUS软件有限元数值分析结果对弯矩-转角恢复力模型进行了验证,分析了低周往复荷载作用下SCRF阻尼器的滞回性能,并进行了参数分析。结果表明:有限元计算结果与阻尼器恢复力模型结果吻合良好;提高接触面间的摩擦因数与斜面高度可以提高阻尼器的最大承载力、耗能能力、有效刚度,但是超过一定限值的斜面高度会降低阻尼器的自复位能力;施加SMA螺栓预紧力可以提高阻尼器的摩擦启动弯矩,对于阻尼器的耗能能力与最大承载力影响不大。

变摩擦装配式自复位复合墙抗震性能研究

针对自复位墙体耗能不足及大位移角时损伤严重的问题,介绍了一种变摩擦装配式自复位复合墙.墙体由变摩擦阻尼器、钢脚、预应力筋和复合墙构成:变摩擦阻尼器的摩擦力随滑移量的增加而增加,具有良好的耗能能力;钢脚提高了墙角抗压强度并提供了变摩擦阻尼器安装空间;预应力筋为墙体提供了自复位能力和部分承载能力;复合墙具有轻质、高强、绿色环保的特点.为进一步研究该墙体的抗震性能,对3块自复位复合墙进行了低周往复试验,分析不同初始预应力、碟簧组合形式对试件破坏形态、滞回特征、承载力、刚度退化、自复位能力和耗能能力的影响.研究结果表明:试件仅在墙底部出现少量混凝土表皮剥落,表现出良好的低损伤特点;试件在1.0%位移角时最大残余位移角为0.85%,表现出自复位特点;各试件的单圈耗能随着位移角的增加而迅速增加,表现出良好的耗能能力;初始预应力提高至1.9倍,导致承载力增加至1.3倍,而残余位移角降低至60%;阻尼器碟簧组合的并联数量增加至2倍,导致墙体的承载力增加至1.5倍,耗能能力增加至2倍,残余位移角增加至4.6倍.此外,建立了自复位复合墙数值分析模型,数值模型分析结果与试验结果较为吻合.随后进行了参数分析,发现预应力筋根数、螺栓初始预紧力和钢脚宽度对墙体的承载能力或耗能能力具有较大影响.

罕遇地震下高速铁路大跨矮塔斜拉桥减隔震性能研究

为研究不同减隔震装置对高速铁路大跨矮塔斜拉桥的减隔震机理,以某(90+180+90)m矮塔斜拉桥为研究背景,基于非线性时程分析建立有限元模型,研究摩擦摆支座、黏滞阻尼器和减隔震组合装置的减震效果及桥梁的抗震性能。结果表明:罕遇地震作用下,全桥主塔处采用摩擦摆支座和黏滞阻尼器的组合装置可以有效解决抗震问题,优化后选取摩擦系数为0.06、曲率半径为2 m的摩擦摆支座和阻尼系数为12000 kN·(m·s^(-1))-α、阻尼指数α为0.8的黏滞阻尼器;相比于单独使用摩擦摆支座或黏滞阻尼器,减隔震组合装置可大幅度减小全桥各关键截面的内力、桥墩位移及梁端转角,显著提升桥梁的抗震性能,剪力和弯矩的减震率分别达70.85%和76.94%,桥墩墩顶位移减震率达76.08%;各关键截面安全系数均大于1,结构均处于弹性范围,满足桥梁抗震性能的要求。

基于负刚度装置的超长联大跨连续梁桥地震反应控制研究

为完善超长联大跨连续梁桥的减、隔震技术,将负刚度装置引入到超长联大跨隔震连续梁桥中组成新型减、隔震系统,并与黏滞阻尼器-摩擦摆支座组合减震系统进行比较。基于CSiBridge软件建立全桥有限元模型,负刚度装置采用弹性多段线模拟,摩擦摆支座采用双线性恢复力模型,黏滞阻尼器采用Maxwell模型,输入3条地震波进行非线性时程分析,考查两种新型减、隔震系统下桥梁结构的地震反应,探究负刚度系统及黏滞阻尼器系统对超长联大跨连续梁桥地震反应的控制效果。研究结果表明:负刚度装置与黏滞阻尼器均可以有效地减小超长联大跨隔震连续梁桥的支座位移。负刚度装置对桥墩内力反应及梁体加速度反应的控制优于黏滞阻尼器。负刚度装置在超长联大跨连续梁桥地震反应控制中有较好的应用前景。

基于转动摩擦铰阻尼器的干式装配梁-柱节点抗震性能试验

基于转动摩擦铰阻尼器(RFHD),提出了转动摩擦耗能干式装配梁-柱节点(DRFDBJ)。为了验证DRFDBJ结构对于实现预期力学性能的可行性和合理性,以施加在摩擦片表面的螺栓预紧力(P_(c))为变量,开展了2个工况下的DRFDBJ试件低周往复拟静力试验研究。结果表明:DRFDBJ结构的力学性能主要由RFHD提供并控制,试验中节点呈现了稳定的承载力和理想的变形、耗能能力,并实现了预期的损伤集中;2个不同P_(c)水准下节点承载力的试验值与理论值误差不超过5%,通过调整P_(c)可实现节点承载力的调控,为DRFDBJ结构承载力的可调控提供了支撑。

高烈度震区大跨径中承式钢箱系杆拱桥减隔震技术研究

为了研究高强度地震作用下大跨径中承式钢箱系杆拱桥地震响应及减隔震技术,以西双版纳黎明大桥为工程背景,选取类似场地的实际地震动记录作为输入地震波,采用非线性时程分析法,研究支座类型及参数变化对拱桥结构的减隔震效果。结果表明:相比于普通支座,减隔震支座能大幅降低结构内力,但纵向位移有所增加,且摩擦摆支座的减隔震效果要强于铅芯橡胶支座;摩擦摆支座+黏滞阻尼器联合抗震体系能够有效降低纵向和横向位移,进一步能提升桥梁的抗震性能;对联合抗震体系进行参数敏感性分析可知:最佳的参数范围是:摩擦因数为0.04,曲率半径在3 200~4 200 mm,阻尼系数为6 000,阻尼指数在0.2~0.4;在最优抗震体系下,结构位移和内力均显著降低,最大减震率分别达到了75.3%和82.3%,表明该体系大幅提高了拱桥抵抗地震的能力,为同类桥梁减隔震设计提供参考。

复杂工况下储能飞轮转子传力支承与减振设计

针对复杂工况下飞轮转子上、下传力支承角接触球轴承与支座间隙配合导致的振动问题,以及真空环境下振动控制问题,提出飞轮转子上支承采用圆柱滚子轴承,下支承采用深沟球轴承+成对角接触球轴承联合传力支承方案,解决了复杂工况下轴向力调整、磁轴承失效、轴向力平衡、支承刚度连续、支承系统变形协调等结构设计难题。同时引入一种主控式弹支干摩擦阻尼器(ESDFD),抑制转子径向振动。采用有限元法建立ESDFD-储能飞轮转子系统耦合动力学模型,计算飞轮转子动力学特性,分析单/双阻尼器对转子振动的控制效果。结果表明:针对转子一阶、二阶模态振动,采用单/双阻尼器控制方式,最大响应均低于30μm,减振比超过90%。

新型组合隔震支座设计与性能研究

在已有研究基础上,为提高摩擦型组合隔震支座变形能力、改进各摩擦组件位移协调性,建立实体化和参数化计算模型,对新型三段两级摩擦组合隔震支座进行构造及内力分析研究,使用ABAQUS软件对摩擦阻尼器和组合隔震支座进行实体有限元模拟。针对设置常规隔震支座和新型组合隔震支座的某隔震结构案例进行建模及非线性时程地震响应分析,推导组合隔震支座出力和构造参数的关系。研究结果表明,文章所采用的摩擦阻尼器参数化建模方法是准确的,新型组合支座可明显降低支座拉应力,减小隔震层位移,提高结构抗倾覆能力。文章提出的针对摩擦阻尼器的简化单元可大幅提高有限元模型的计算效率。