Wind tunnel study of the across-wind response of a slender tower with a nonlinear tuned mass damper

The effectiveness of a class of nonlinear tuned mass dampers (TMDs) in suppressing across-wind structure oscillations was examined through a wind tunnel test. The nonlinear TMD employed a wire rope spring to replace both the spring and the damper required in a typical system. First, a single degree of freedom aeroelastic stick model of a slender structure with a square cross-section was tested under different levels of damping. The measurements obtained from the tests were used to determine the root-mean-square (RMS) of the lift coefficient and other aerodynamic parameters. In the second phase of testing, the nonlinear TMD system was attached near the tip of the aeroelastic model. The response reduction achieved by adding the TMD was considerable and was quantitatively expressed in terms of an equivalent viscous damping. A comparison between the nonlinear TMD and an equivalent optimized linear TMD was made. Probability-based procedures were developed to estimate the equivalent damping provided by the nonlinear TMD. The estimated damping was compared with that obtained experimentally to evaluate the accuracy of the prediction method.     

Suppression of bridge flutter using tuned mass dampers based on robust performance design

This study addresses design methodologies of TMDs for control of bridge flutter, considering the uncertainty of aerodynamic data in order to enhance the robustness of tuned mass dampers (TMDs) against frequency drift caused by wind-bridge interaction. To evaluate the robust performance of a TMD system, the concept of minimum flutter velocity is introduced in the presence of perturbed unsteady aerodynamic forces. Two types of multiple tuned mass dampers (MTMD) are considered, i.e. the frequencies of each TMD are regularly or irregularly spaced. An optimization procedure for an irregular MTMD (IMTMD), which has an unequal frequency interval and different damping ratio of each individual TMD, is proposed based on genetic algorithms. The proposed TMDs are then applied to a cable stayed bridge and a suspension bridge to prove the validity of the methods. From the numerical results, the proposed IMTMD shows remarkable control efficiency compared with conventional single TMD (STMD) and MTMD.     

Designing optimal tuned mass dampers for nonlinear frames by distributed genetic algorithms

In this paper, the capabilities of tuned mass dampers (TMDs) for the mitigation of response of nonlinear frame structures subjected to earthquakes have been studied. To determine the optimal parameters of a TMD, including its mass, stiffness and damping, we developed an optimization algorithm based on the minimization of a performance index, defined as a function of the response of the nonlinear structure to be controlled. Distributed genetic algorithm has been used to solve the optimization problem. For illustration, the method has been applied to the design of a linear TMD for an eight‐story nonlinear shear building with bilinear hysteretic material behavior subjected to earthquake. The results have shown that the method has been successful in determining the TMD parameters to reduce the structure response. The simplicity and desirable convergence behavior of the method have also been two important results of the method. Two performance indices have been defined: (a) the minimization of the maximum drift and (b) the accumulated hysteretic energy. It has also been shown that the efficiency of the TMD has been influenced by the mass ratio of the TMD, the maximum TMD stroke length and the TMD design earthquake. Copyright © 2011 John Wiley & Sons, Ltd.     

大尺寸超弹性镍钛形状记忆合金螺旋弹簧滞回性能

利用2种镍钛形状记忆合金(SMA)研制了大尺寸超弹性螺旋弹簧,对其进行了单轴反复荷载作用下的滞回性能试验,研究了超弹性SMA螺旋弹簧的恢复力特性与耗能能力,分析了加载频率、位移幅值对2种SMA螺旋弹簧滞回曲线以及等效刚度、单位循环耗能、等效阻尼比和残余位移等力学性能参数的影响;采用刚弹性模型和Bouc-Wen模型,建立了适用于整体结构分析的SMA螺旋弹簧简化恢复力模型,并利用该模型进行了数值模拟。结果表明:超弹性SMA螺旋弹簧具有稳定的滞回曲线,且具有良好的复位性能和大变形能力,可用于结构自复位控制装置的研发;数值模拟结果与试验结果吻合较好,验证了简化恢复力模型的正确性。     

Optimal design of hysteretic dampers connecting adjacent structures using multi-objective genetic algorithm and stochastic linearization method

An optimal design method is proposed for nonlinear hysteretic dampers that enhance the seismic performance of two adjacent structures. The proposed method employs nonlinear random vibration analyses by use of a stochastic linearization method in order to efficiently estimate the stochastic responses of coupled buildings without performing numerous nonlinear time-history analyses. The main objectives of the optimal design are not only to reduce the seismic responses but also to minimize the total cost of the damper system. To deal with such conflicting objectives, a multi-objective genetic algorithm is adopted. This approach systematically obtains a set of Pareto optimal solutions that are non-inferior or non-superior to each other. The process for choosing a reasonable design from the optimal surface of Pareto solutions is also discussed. As an example of a nonlinear hysteretic damping device, this study considers passive-type magneto-rheological dampers with fixed input voltages. The optimal voltages and numbers of installed dampers are simultaneously determined. The robustness of the optimal design against uncertain characteristics of ground motions is examined through extensive nonlinear random vibration analyses.     

Influence of soil‐structure interaction on performance of a super tall building using a new eddy‐current tuned mass damper

Tuned mass dampers (TMDs) can be used as vibration control devices to improve the vibration performance of high‐rise buildings. The Shanghai Tower (SHT) is a 632‐m high landmark building in China, featuring a new eddy‐current TMD. Special protective mechanisms have been adopted to prevent excessively large amplitude of the TMD under extreme wind or earthquake loading scenarios. This paper presents a methodology for simulating behavior of the new eddy‐current TMD that features displacement‐dependent damping behavior. The TMD model was built into the SHT finite element model to perform frequency analysis and detailed response analyses under wind and earthquake loads. Furthermore, soil‐structure interaction (SSI) effects on wind and seismic load responses of the SHT model were investigated, as SSI has a significant impact on the vibration performance of high‐rise buildings. It was found that SSI has more significant effects on acceleration response for wind loads with a short return period than for wind loads with a long return period. Some of the acceleration responses with SSI effects exceed design limits of human comfort for wind loads with shorter return periods. As to the seismic analyses, it was found that SSI slightly reduces the displacement amplitude, the damping force, and the impact force of the TMD.     

胶合木梁-柱摩擦型节点滞回性能研究

将摩擦型连接和形状记忆合金（SMA）板引入重型胶合木结构,提出了胶合木梁-柱摩擦型节点并研究了其滞回性能。分别以钢材和木材作为摩擦板材料,设计并制作了3个1∶2缩尺节点,开展了水平低周反复加载试验,获取了节点的典型破损模式和弯矩-转角滞回曲线,对比了节点的弹性转动刚度、峰值弯矩、耗能能力和残余变形。基于胶合木梁-柱摩擦型节点的工作机理建立了节点弯矩-转角滞回模型。结果表明：摩擦型节点主要发生SMA板受拉断裂,节点连接区域木材基本保持完好。相比普通螺栓钢填板节点,摩擦型节点的弹性转动刚度基本保持不变,峰值弯矩下降2%~17%,但各级位移加载幅值下节点耗能增加64%~278%,等效黏滞阻尼系数基本大于0.2,残余变形减小。采用钢制摩擦板的摩擦型节点残余变形更小,采用木质摩擦板的摩擦型节点的等效黏滞阻尼系数较大。胶合木梁-柱摩擦型节点的弯矩-转角滞回模型与试验滞回曲线吻合良好,表明其可用于工程结构分析。     

Hysteretic performance of frictional glulam beam-to-column connections

将摩擦型连接和形状记忆合金（SMA）板引入重型胶合木结构，提出了胶合木梁-柱摩擦型节点并研究了其滞回性能。分别以钢材和木材作为摩擦板材料，设计并制作了3个1∶2缩尺节点，开展了水平低周反复加载试验，获取了节点的典型破损模式和弯矩-转角滞回曲线，对比了节点的弹性转动刚度、峰值弯矩、耗能能力和残余变形。基于胶合木梁-柱摩擦型节点的工作机理建立了节点弯矩-转角滞回模型。结果表明：摩擦型节点主要发生SMA板受拉断裂，节点连接区域木材基本保持完好。相比普通螺栓钢填板节点，摩擦型节点的弹性转动刚度基本保持不变，峰值弯矩下降2%~17%，但各级位移加载幅值下节点耗能增加64%~278%，等效黏滞阻尼系数基本大于0.2，残余变形减小。采用钢制摩擦板的摩擦型节点残余变形更小，采用木质摩擦板的摩擦型节点的等效黏滞阻尼系数较大。胶合木梁-柱摩擦型节点的弯矩-转角滞回模型与试验滞回曲线吻合良好，表明其可用于工程结构分析。     

Parametric control of structural responses using an optimal passive tuned mass damper under stationary Gaussian white noise excitations

In this study, the structural control strategy utilizing a passive tuned mass damper (TMD) system as a seismic damping device is outlined, highlighting the parametric optimization approach for displacement and acceleration control. The theory of stationary random processes and complex frequency response functions are explained and adopted. For the vibration control of an undamped structure, the optimal parameters of a TMD, such as the optimal tuning frequency and optimal damping ratio, to stationary Gaussian white noise acceleration are investigated by using a parametric optimization procedure. For damped structures, a numerical searching technique is used to obtain the optimal parameters of the TMD, and then the explicit formulae for these optimal parameters are derived through a sequence of curve-fitting schemes. Using these specified optimal parameters, several different controlled responses are examined, and then the displacement and acceleration based control effectiveness indices of the TMD are examined from the view point of RMS values. From the viewpoint of the RMS values of displacement and acceleration, the optimal TMDs adopted in this study shows clear performance improvements for the simplified model examined, and this means that the effective optimization of the TMD has a good potential as a customized target response-based structural strategy.     

Integrated damping systems for tall buildings: tuned mass damper/double skin facade damping interaction system

As today's tall buildings become ever taller and more slender, wind‐induced vibration is a serious design issue. This paper presents integrated damping systems for tall buildings. An emphasis is placed on investigating the potential of double skin facades (DSF) as an integrated damping system for tall buildings. In the first scheme, the connectors between the inner and outer skins of the DSF system are designed to have low axial stiffness with a damping mechanism. Through this design, vibration of the primary building structure can be substantially reduced. However, excessive movements of the DSF outer skin masses are a design limitation. In the second scheme, the tuned mass damper (TMD) and DSF damping (DSFD) interaction system is studied to mitigate the design limitation of the first scheme and to resolve other TMD‐related design issues. TMDs are usually very large and located near the top of tall buildings for their effective performance. As a result, very valuable occupiable space near the top of tall buildings is sacrificed to contain large TMDs. In addition, installing TMD systems means adding additional masses to tall buildings. Through the TMD/DSFD interaction system, these issues can also be substantially addressed. Compared with the conventional TMD system, the TMD/DSFD interaction system requires a significantly reduced TMD mass ratio to achieve the same target damping ratio. Compared with the first scheme only with the DSFD mechanism, movements of the DSF outer skins can be better controlled in the TMD/DSFD interaction system. Copyright © 2015 John Wiley & Sons, Ltd.     

Numerical studies on the application of tuned liquid dampers with screens to control seismic response of structures

Tuned liquid damper (TLD) systems are nowadays increasingly being used as one of the economical and effective passive vibration absorbers. A TLD system consists of a water tank having the fundamental sloshing fluid frequency tuned to the frequency near to the natural frequency of structure. This research focuses on modelling tall buildings equipped with TLDs having inside screens subjected to strong ground motions. Strong excitation can cause wave‐breaking phenomenon and makes turbulent in shallow rectangular tanks which could also contribute to the additional damping due to TLDs. On the other hand, wire screens placed inside a liquid tank can play an important role in reducing the structural response due to increasing the inherent damping of the structure. Based on equalizing dissipated energies, a TLD equipped with internal screens can be modelled by equivalent amplitude‐dependent tuned mass damper (TMD). In this study, adopting this simple method, equations of motion for shear‐type buildings equipped with nonlinear amplitude‐dependent TMDs were developed. A complex modal analysis procedure was used to solve the governing equations. Coupling of TMD properties and structural response was solved with iteration on structural response and updating TMD properties. Performing a set of parametric studies on three proposed tall structures equipped with TLD subjected to different ground excitations showed that if the TLD is tuned to a frequency close to the natural frequency of the structure considering hardening behaviour of TLD, it could significantly reduce the seismic response (displacements and base shears) of the structures. Copyright © 2009 John Wiley & Sons, Ltd.     

Coupled‐two‐beam discrete model for dynamic analysis of tall buildings with tuned mass dampers including soil–structure interaction

An equivalent coupled‐two‐beam discrete model is developed for time‐domain dynamic analysis of high‐rise buildings with flexible base and carrying any number of tuned mass dampers (TMDs). The equivalent model consists of a flexural cantilever beam and a shear cantilever beam connected in parallel by a finite number of axially rigid members that allows the consideration of intermediate modes of lateral deformation. The equivalent model is applied to a shear wall–frame building located in the Valley of Mexico, where the effects of soil–structure interaction (SSI) are important. The effects of SSI and TMDs on the dynamic properties of the shear wall–frame building are shown considering four types of soil (hard rock, dense soil, stiff soil, and soft soil) and two passive damping systems: a single TMD on its top (1‐TMD) and five uniformly distributed TMDs (5‐TMD). The results showed a great effectiveness of the TMDs to reduce the lateral seismic response and along‐wind response of the shear wall–frame building for all types of soils. Generally speaking, the dynamic response increases as the flexibility of the foundation increases.     

Seismic response control of high arch dams including contraction joint using nonlinear super-elastic SMA damper

In this study, the shape memory alloy (SMA) restrainer bars utilized to reduce the seismic response of arch dams with vertical contraction joints were investigated. The SMA damper model and the nonlinear behavior of arch dams affected by contraction joint opening/closing during earthquakes were simulated in ANSYS. Moreover, the nonlinear damping control principle and method were discussed. The effectivity of the SMA restrainer bars in arch dams was assessed through comparing with a traditional measure of reinforced steel across contraction joints. The SMA restrainer bars were effective in limiting the relative openings of the contraction joints and reducing the seismic acceleration. In addition, the new SMA vibration damper devices of arch dams are simple and easy to install.     

砌体结构TMD减震体系非线性地震反应研究

根据随机振动理论推导了多层剪切型结构TMD减震系统的随机地震响应,分析了参数的变化对TMD减振系统减震效果的影响,从而优化了取得最佳减震效果所需要的关键参数.以砖砌体结构为研究对象,建立了用于非线性地震反应的三线型骨架曲线及其滞回规律,编制了非线性地震反应分析程序,计算了一幢六层砌体结构减震前和采用TMD减震后的地震反应,分析结果表明,在7度多遇烈度和7度基本烈度地震动作用下减震效果良好,在7度罕遇烈度地震动作用下,TMD系统应通过加强构造措施保证抗震性能.     

Study on adaptive‐passive eddy current pendulum tuned mass damper for wind‐induced vibration control

Tuned mass dampers (TMDs) are used to control wind‐excited responses of high‐rise building as traditional vibration control devices. A TMD will have an excellent control effect when it is well tuned. However, a traditional passive TMD is sensitive to the frequency deviation; the mistuning in frequency and damping ratio both will decrease its control effect. In the previous research, an adaptive‐passive variable pendulum TMD (APVP‐TMD) is proposed, which can identify the TMD optimal frequency and retune itself through varying its pendulum length. However, it is found that the frequency variation will change the TMD damping ratio, and an unreasonable damping ratio will lead to a decrement in the robustness of a TMD. In this study, an adaptive‐passive eddy current pendulum TMD (APEC‐PTMD) is presented, which can retune the frequency through varying the pendulum length, and retune the damping ratio through adjusting the air gap between permanent magnets and conductive plates. An adjustable eddy current pendulum TMD (PTMD) is tested, and then, a single‐degree‐of‐freedom (SDOF) primary model with an APEC‐PTMD is built, and functions of frequency and damping ratio retuning are verified. The 76‐story wind‐sensitive benchmark model is proposed in the case study. The original model without uncertainty and ±15% stiffness uncertainty models are considered, and response control effects of different controllers are compared. Results show that because the APEC‐PTMD can both retune its frequency and damping ratio; it is more robust and effective than a passive TMD. It is also found that the APEC‐PTMD has a similar control effect with the active TMD, with little power consumption and better stability.     

基于设计反应谱的空间结构弹塑性地震反应分析方法

空间结构非线性等效单自由度体系的荷载-位移曲线后屈服段较短,采用等能量方法将其转化为双折线时易产生较大计算误差,且双折线拐点需迭代确定。针对此问题,采用Ramberg-Osgood模型描述空间结构等效单自由度体系荷载-位移滞回曲线;基于等效线性化方法,采用最大位移对应的割线刚度作为等效线性体系刚度k_e;对滞回曲线积分得到滞回环面积,令滞回耗能与等效线性体系阻尼耗能相等,导出等效黏滞阻尼ζ_e。将线性加速度设计反应谱变换为T(周期)-ζ(阻尼比)-d(位移)格式,与空间结构等效线性体系的T_e(等效周期)-ζ_e-d曲线联立,用图解法直接计算等效线性体系的地震位移反应,并进一步得到空间结构的整体地震反应。采用所提出的方法计算柱面网壳和球面网壳结构的非线性地震反应。结果表明：该方法简洁高效,无需迭代,易于编程实现,对空间结构地震位移反应求解精度较高。     

Optimum design of multiple positioned tuned mass dampers for structures constrained with axial force capacity

The stories of structure may have different and limited axial force capacity. In order to passively control the translational movement of structures, a tuned mass damper (TMD) positioned on a story may cause to exceed axial force capacity of a story. The optimum performance is achieved when all additional masses are positioned on the top story. Whereas, the top stories of structure may be constructed with lower axial force capacity than the lower stories. In that case, the maximum allowed TMD mass for upper stories may be low. In that situation, several TMDs may be positioned on several stories. In the current study, the optimum tuning of TMDs positioned on multiple stories of structure is investigated. By using small masses, it is also possible to obtain effective passive control with dampers that have small damping coefficients comparing with a single TMD on the top of the structure. The design variables of the optimization problem such as the period and damping ratio of TMD are tuned according to a metaheuristic algorithm called flower pollination algorithm. The TMD is optimized for near‐fault excitations by using impulsive motions during the optimization process. The proposal was applied to four case studies. According to the results, the multiple positioned TMDs may be a practical and effective option comparing with the use of a single heavy TMDs on the top of a structure.     

A simple hybrid damping device with energy‐dissipating and re‐centering characteristics for special structures

The usage of special materials with unique properties in seismic resistant structures has increased since the 1994 Northridge earthquake to overcome limited energy dissipation and ductility. Among them, shape memory alloy (SMA) is a unique metallic alloy that has the ability to undergo large deformations and revert back to its original un‐deformed shape. Thus, a simple and practical hybrid damping device equipped with SMA that provides both energy‐dissipating and re‐centering (strain‐recovering) capabilities is developed and evaluated in the present paper. Quasi‐static loading tests on Nitinol bars are conducted to obtain their mechanical properties in tension and compression. The optimum proportion of SMA and steel in the device is achieved through analyzing various models. Placing the proposed device in semi‐rigid bracing members of special structures will localize the energy‐dissipating and ductility while providing the brace with strain‐recovering capability. Copyright © 2012 John Wiley & Sons, Ltd.     

基于阻尼的地震循环荷载作用下黏土非线性模型

提出一种基于阻尼比的黏土动应力应变模型,通过在滞回曲线中显示地引入代表阻尼比大小的形状系数,使得理论滞回曲线真实地反应土体的滞回阻尼性能。首先推导在等幅对称荷载下滞回曲线的理论方程。然后,为将该模型应用于随机地震荷载的情况,对扩展的曼辛不规则加卸载准则进行了改造,提出当沿小圈加载时,滞回曲线奔向曾经到达过的最大加卸载点。最后,介绍对一种粉质黏土进行的等幅循环荷载和不规则荷载作用下的循环单剪试验。试验结果表明,模型能够较好地模拟土在地震循环荷载作用下的滞回特性。