Experimental beyond design and residual performances of full-scale viscoelastic dampers and their empirical modeling

Most past researches relevant to viscoelastic (VE) dampers, regardless of analytical and experimental ones, aimed at their design (or pre-damage) performance. In reality, however, under maximum considered or greater shaking caused by earthquakes, the shear deformation of the VE dampers installed in a structure may exceed or is even much larger than their nominal design range, thus leading to damage to the VE material. Under this circumstance, the structural design might become not conservative when the viscoelastically damped structure is a retrofit design or is not a supplemental damping design. Therefore, in this study, the beyond design and residual performances of the full-scale VE dampers after suffering damage are experimentally probed and compared with their design (or pre-damage) performance tested before. To have more engineering sense in practice, some suitable and conservative empirical post-damage models through considering reduction factors in the Kelvin-Voigt model for assessing the beyond design and residual performances of the full-scale VE dampers after suffering damage are recommended.     

Experimental and analytical study on the performance of particle tuned mass dampers under seismic excitation

A particle tuned mass damper (PTMD), which is a creative integration of a traditional tuned mass damper and an efficient particle damper in the vibration control area, is proposed. This paper presents a comprehensive study that involves experimental, analytical, and computational approaches. The vibration control effects of a PTMD that is attached to a five‐story steel frame under seismic input are investigated by a series of shaking table tests. The influence of some parameters (auxiliary mass ratio, gap clearance, mass ratio of particles to the total auxiliary mass, frequency characteristics, and amplitude level of the input) is explored, and the performance of the PTMD with/without buffered material is compared. The experimental results show that the PTMD can achieve significant damping effects under seismic excitations, and the bandwidth of the suppression frequency is expanded, showing the device's robustness and control efficiency. In addition, an approximately analytical solution that is based on the concept of an equivalent single‐particle damper is presented, and the method to determine the corresponding system parameters is introduced. A comparative study between experimental and numerical results is conducted to verify the feasibility and accuracy of this analytical model. Copyright © 2016 John Wiley & Sons, Ltd.     

基于正交设计的粘弹性阻尼器参数优化

粘弹性阻尼器耗能能力受其剪切储存模量、剪切损失模量、剪切面积、粘弹性层厚度等多种参数的影响.为了探讨耗能器的减震控制效果,将现代振动控制理论和正交设计相结合,以结构顶层各点的最大位移和最大加速度为评价指标,在不同的参数水平下对某5层框架结构进行动态仿真,并给出各种参数对结构振动控制的贡献.计算结果表明,粘弹性阻尼器可以有效地控制框架结构的地震响应,选择合适的材料参数,位移峰值衰减可高达90.8%,加速度峰值衰减可高达63.8%.     

Optimal design of viscoelastic dampers using eigenvalue assignment

In this study a procedure for determining the optimum size and location of viscoelastic dampers is proposed using the eigenvalue assignment technique. Natural frequencies and modal damping ratios, required to realize a given target response, are determined first by the convex model. Then the desired dynamic structural properties are realized by optimally distributing the damping and stiffness coefficients of viscoelastic dampers using non‐linear programming based on the gradient of eigenvalues. This optimization method provides information on the optimal location as well as the magnitude of the damper parameters. The proposed procedure is applied to the retrofit of a 10‐story shear frame, and to a three‐dimensional structure with an asymmetric plan. The analysis results confirm that the responses of model structures retrofitted by the proposed method correspond well with the given target response. Copyright © 2003 John Wiley & Sons, Ltd.     

Optimal design of added viscoelastic dampers and supporting braces

This paper presents a simultaneous optimization procedure for both viscoelastic dampers (VEDs) and supporting braces installed in a structure. The effect of supporting braces on the control efficiency of VEDs is also investigated. To apply a general gradient‐based optimization algorithm, closed‐form expressions for the gradients of objective function and constraints are derived. Also, the constraint on the dynamic behavior of a structure is embedded in the gradient computation procedure to reduce the number of variables in the optimization. From numerical analysis of an example structure, it was found that when sufficient stiffness cannot be provided for the supporting braces, the flexibility of the brace should be taken into account in the design of the VED to achieve the desired performance of the structure. It was also observed that, as a result of the proposed optimization process, the size of the supporting brace could be reduced while the additional VED size (to compensate for the loss of the control effect) was insignificant. Copyright © 2003 John Wiley & Sons, Ltd.     

基于性能的黏弹性阻尼器减震结构抗震设计

根据黏弹性阻尼器的特点和抗震规范的要求,分别提出了用于黏弹性阻尼器减震结构抗震分析的弹性及弹塑性需求谱,前者是基于黏弹性阻尼器减震结构等效阻尼比的简化计算公式及规范规定的反应谱;后者是基于修正的V id icRμ-μ-T关系。在此基础上,借助模态推覆分析,提出了可以考虑高阶振型影响的黏弹性阻尼器消能减震结构体系的能力谱分析方法,并对一8层钢筋混凝土消能减震框架结构进行了"中震不坏,大震可修"性能水准下的抗震分析。算例结果表明,采用该方法分析黏弹性阻尼器减震结构体系是可行的、有效的。     

工程结构粘弹性消能支撑型式及设计参数的研究

针对工程中的实际需要,提出一些新型的粘弹性消能支撑型式,分析了它们的受力特点,推导了消能支撑变形的表达式,并给出了其控制力的计算公式;最后,研究了影响结构消能效果的设计参数,给出了设计参数合理的取值范围。     

An alternative practical design method for structures with viscoelastic dampers

Viscoelastic dampers (VEDs) are one of the most common passive control devices used in new and retrofit building projects which reduce the structure responses and dissipate seismic energy during an earthquake. Various methods to design this kind of dampers have been proposed based on the desired level of additional damping, eigenvalue assignment, modal strain energy, linear quadratic regulator control theories, and other approaches. In the current engineering practice, the popular method is the one based on the modal strain energy that uses the inter-story lateral stiffness as one of the main variables for damper design. However, depending on the configuration of the structure, in some cases the resulting interstory lateral stiffness can be very large. Consequently, the dampers size would also be large producing much more damping than that effectively necessary, resulting in an increase of the overall cost of the supplemental damping system and causing excessive stress on the structural elements connected to the dampers. In this paper an alternative practical design method for structures with VEDs is proposed. This method uses the inter-story shear forces as one of the main variables to accomplish the damper design compared to what was done in previous studies. Nonlinear time-history analyses were conducted on a 7-story reinforced concrete (RC) structure to check the reliability and effectiveness of the proposed method. Comparisons on the seismic performance between the structure without dampers and that equipped with VEDs were carried out. It is concluded that the proposed method results in a very suitable size of dampers, which are able to improve the performance of the structure at all levels of earthquake ground motions and satisfying the drift requirement prescribed in the codes.     

Experimental and analytical study on pounding reduction of base‐isolated highway bridges using MR dampers

Pounding between adjacent superstructures has been a major cause of highway bridge damage in the past several earthquakes. This paper presents an experimental and analytical study on pounding reduction of highway bridges subjected to earthquake ground motions by using magnetorheological (MR) dampers. An analytical model, which incorporates structural pounding and MR dampers, is developed. A series of shaking table tests on a 1:20 scaled base‐isolated bridge model are performed to investigate the effects of pounding between adjacent superstructures on the dynamics of the structures. Based on the test results, the parameters of the linear and the nonlinear viscoelastic impact models are identified. Performance of the semiactive system for reducing structural pounding is also investigated experimentally, in which the MR dampers are used in conjunction with the proposed control strategy, to verify the effectiveness of the MR dampers. Structural responses are also simulated by using the established analytical model and compared with the shaking table test results. The results show that pounding between adjacent superstructures of the highway bridge significantly increases the structural acceleration responses. For the base‐isolated bridge model considered here, the semiactive control system with MR dampers effectively precludes pounding. Copyright © 2009 John Wiley & Sons, Ltd.     

铅粘弹性阻尼器性能试验研究

本文介绍了作者提出的铅粘弹性阻尼器的构造和原理，对铅粘弹性阻尼器在不温度，频率，应应幅值和粘弹性层厚度的情况下进行了试验，分析研究了温度，频率，应变幅值和粘弹性层度对铅粘弹性阻尼器性能的影响规律，同时，对铅粘弹性阻尼器进行了低周疲劳试验和大变形试验，考察了铅粘弹性阻尼器的疲劳性能和极限变形能力，最后给出了有关的结论和建议。     

足尺变刚度控制系统性能试验与计算模型

本文充分考虑了实际工程应用中的诸多因素,成功地研制了40吨足尺变刚度控制系统并对其进行了性能试验,实现了模型试验到实用样机的转化,性能试验结果表明,该足系统的性能满足各项设计技术要求,系统滞回曲线说明系统充分发挥了可变刚度的吸能,释能减振控制作用,在此基础上,文中研究了足尺系统的设计与控制算法,试验工况与试验结果以及计算模型。     

Simplified design procedure for frame buildings with viscoelastic or elastomeric structural dampers

A simplified design procedure (SDP) for preliminary seismic design of frame buildings with structural dampers is presented. The SDP uses elastic‐static analysis and is applicable to structural dampers made from viscoelastic (VE) or high‐damping elastomeric materials. The behaviour of typical VE materials and high‐damping elastomeric materials is often non‐linear, and the SDP idealizes these materials as linear VE materials. With this idealization, structures with VE or high‐damping elastomeric dampers can be designed and analysed using methods based on linear VE theory. As an example, a retrofit design for a typical non‐ductile reinforced concrete (RC) frame building using high‐damping elastomeric dampers is developed using the SDP. To validate the SDP, results from non‐linear dynamic time history analyses (NDTHA) are presented. Results from NDTHA demonstrate that the SDP estimates the seismic response with sufficient accuracy for design. It is shown that a non‐ductile RC frame building can be retrofit with high‐damping elastomeric dampers to remain essentially elastic under the design basis earthquake (DBE). Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental study on full-scale steel beam-to-column moment connections

Ten full-scale steel beam-to-column moment connections used in moment-resisting frames （MRFs） were tested to study the failure process, failure mode, strength and plastic rotation capacity. The specimens include one traditional welded flange-bolted web connection, one traditional fully welded connection, four beam flange strengthened connections, three beam flange weakened connections, and one through-diaphragm connection. The test results show that the connections with flange cover plates or with partly cut beam flanges satisfy the beam plastic rotation demand for ductile MRFs. From the measured stress profiles along the beam flange and beam web depth, the mechanics of brittle fracture at the end of the beam is discussed. Design recommendations for steel beam-to-column moment connections are proposed.     

铅橡胶复合阻尼器的性能试验研究

介绍作者提出的铅橡胶复合阻尼器的构造与耗能原理，通过不同形状，不同大小铅心的8个铅橡胶复合阻尼器的循环荷载试验，研究了频率、应变幅值、循环次数、铅芯直径、竖向压力等对铅橡胶复合阻尼器的影响规律。研究结果表明，铅橡胶复合阻尼器工作性能稳定，耗能性能和抗疲劳性能好。     

组合式铅橡胶复合阻尼器的性能试验研究

研究提出了组合式铅橡胶复合阻尼器,对该阻尼器的力学性能和疲劳性能进行了试验研究,分析了频率、应变幅值、铅芯直径、循环次数对阻尼器性能的影响规律。研究结果表明,组合式铅橡胶阻尼器具有很好的工作性能和耗能性能。     

Experimental and analytical studies on multiple tuned mass dampers for seismic protection of porcelain electrical equipment

Porcelain electrical equipment (PEE), such as current transformers, is critical to power supply systems, but its seismic performance during past earthquakes has not been satisfactory. This paper studies the seismic performance of two typical types of PEE and proposes a damping method for PEE based on multiple tuned mass dampers (MTMD). An MTMD damping device involving three mass units, named a triple tuned mass damper (TTMD), is designed and manufactured. Through shake table tests and finite element analysis, the dynamic characteristics of the PEE are studied and the effectiveness of the MTMD damping method is verified. The adverse influence of MTMD redundant mass to damping efficiency is studied and relevant equations are derived. MTMD robustness is verified through adjusting TTMD control frequencies. The damping effectiveness of TTMD, when the peak ground acceleration far exceeds the design value, is studied. Both shake table tests and finite element analysis indicate that MTMD is effective and robust in attenuating PEE seismic responses. TTMD remains effective when the PGA far exceeds the design value and when control deviations are considered.     

Experimental performance evaluation of an equipment isolation using MR dampers

Critical non‐structural equipments, including life‐saving equipment in hospitals, circuit breakers, computers, high technology instrumentations, etc., are vulnerable to strong earthquakes, and the failure of these equipments may result in a heavy economic loss. In this connection, innovative control systems and strategies are needed for their seismic protections. This paper presents the performance evaluation of passive and semi‐active control in the equipment isolation system for earthquake protection. Through shaking table tests of a 3‐story steel frame with equipment on the first floor, a magnetorheological (MR)‐damper together with a sliding friction pendulum isolation system is placed between the equipment and floor to reduce the vibration of the equipment. Various control algorithms are used for this semi‐active control studies, including the decentralized sliding mode control (DSMC) and LQR control. The passive‐on and passive‐off control of MR damper is used as a reference for the discussion on the control effectiveness. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental and analytical investigations of steel panel dampers for seismic applications in steel moment frames

A ductile Vierendeel frame can be constructed by incorporating steel panel dampers (SPDs) into a moment‐resisting frame (MRF). Thus, the stiffness, strength, and ductility of the lateral force–resisting system can be enhanced. The proposed 3‐segment SPD possesses a center inelastic core (IC) and top and bottom elastic joints. This paper discusses the mechanical properties, capacity design method, and buckling‐delaying stiffeners for the SPDs through the use of cyclic loading tests on 2 specimens. Tests confirm that SPDs' cyclic force vs deformation relationships can be accurately predicted using either the Abaqus or PISA3D model analyses. The paper also presents the capacity design method for boundary beams connected to the SPDs of a typical SPD‐MRF. The seismic performance of an example 6‐story SPD‐MRF is evaluated using nonlinear response history analysis procedures and 240 ground accelerations at 3 hazard levels. Results indicate that under 80 maximum considered earthquake ground accelerations, the mean‐plus‐one standard deviation of the shear deformation of the ICs in the SPDs is 0.055 rad, substantially less than the 0.11 rad deformational capacity observed from the SPD specimens. The experimental cumulative plastic deformation of the proposed SPD is 242 times the yield deformation and is capable of sustaining a maximum considered earthquake at least 8 times before failure. This paper introduces the method of using one equivalent beam‐column element for effective modeling of the 3‐segment SPD. The effects of the IC's relative height and stiffness on the overall SPD's elastic and postelastic stiffness, elastic deformation limits, and inelastic deformational demands are discussed.     

Modal equations of linear structures with viscoelastic dampers

Several types of energy dissipation devices using viscoelastic materials have been proposed to reduce vibration in structures subjected to wind and earthquake excitations. At constant temperature and small strain levels, the mechanical behaviour of Viscoelastic (VE) materials can be described using linear operators. In general, the stiffness and damping matrices of structures using VE devices are frequency dependent; this implies that the classical second-order differential equations for the modal co-ordinates are not a complete model for this type of structures. In this paper, the concept of modal coupling in the frequency domain is addressed, expressions for diagonalizable frequency-dependent stiffness and damping matrices are given, and an iterative technique for the computation of the response of viscoelastic structures is studied. Necessary and sufficient conditions for convergence of the technique are given and numerical examples are developed to illustrate the application of the method.     

管壁开孔足尺钢管混凝土柱抗震性能试验研究

针对钢筋混凝土梁与钢管混凝土柱的穿筋连接形式,研究了钢管开穿筋小孔及加固对钢管混凝土柱抗震性能的影响。对于未开孔、开孔和开孔并加固三种情况,进行了3个直径为610 mm的足尺钢管混凝土柱试件的低周反复荷载试验。试验结果表明:未开孔试件在距根部100 mm处发生钢管屈曲破坏;开孔试件的破坏主要是开孔处屈曲撕裂,开孔对钢管混凝土柱初期刚度和峰值承载力影响不大,但在峰值承载力后受孔边撕裂破坏影响,开孔试件的刚度和强度退化较快、延性和耗能能力降低;开孔并加固试件的破坏位置上移至加固段上部约90 mm处,与未开孔试件表现出相似的抗震性能。