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1.
Seismic analysis of structures with a fractional derivative model of viscoelastic dampers 总被引：3，自引：3，他引：0
Viscoelastic dampers are now among some of the preferred energy dissipation devices used for passive seismic response control.
To evaluate the performance of structures installed with viscoelastic dampers, different analytical models have been used
to characterize their dynamic force deformation characteristics. The fractional derivative models have received favorable
attention as they can capture the frequency dependence of the material stiffness and damping properties observed in the tests
very well. However, accurate analytical procedures are needed to calculate the response of structures with such damper models.
This paper presents a modal analysis approach, similar to that used for the analysis of linear systems, for solving the equations
of motion with fractional derivative terms for arbitrary forcing functions such as those caused by earthquake induced ground
motions. The uncoupled modal equations still have fractional derivatives, but can be solved by numerical or analytical procedures.
Both numerical and analytical procedures are formulated. These procedures are then used to calculate the dynamic response
of a multi-degree of freedom shear beam structure excited by ground motions. Numerical results demonstrating the response
reducing effect of viscoelastic dampers are also presented. 相似文献
2.
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. 相似文献
3.
Equivalent damping of SDOF structure with Maxwell damper 总被引：1，自引：1，他引：0
To predict the maximum earthquake response of an SDOF structure with a Maxwell fluid damper or supplemental brace-viscous damper system using the seismic design response spectrum technique, a new approach is presented to determine the first- and second-order equivalent viscous damping and stiffness, the peak responses, and the damper force of the above structure. Based on the fact that the dynamic characteristics of a general linear viscoelastically damped structure are fully determined by its free vibration properties and the relaxation time constants of a Maxwell fluid damper and supplemental brace-viscous damper system in engineering practice are all small, the method of improved multiple time scales and the equivalent criterion in which all free vibration properties are the same are used to obtain the first- and second-order equivalent viscous damping and stiffness of the above structure in closed form. The accuracy of the proposed method is higher and significantly better than that of the modal strain energy method. Furthermore, in the parametric range of the requirements of the Chinese "Code for Seismic Design of Buildings", the error of the proposed second-order equivalent system for the above-mentioned engineering structure is not more than 0.5%. 相似文献
4.
The feasibility of using viscoelastic (VE) dampers to mitigate earthquake-induced structural response is studied in this paper. The properties of VE dampers are briefly described. A procedure for evaluating the VE damping effect when added to a structure is proposed in which the damping effect of VE dampers is incorporated into modal damping ratios through an energy approach. Computer simulation of the damped response of a multi-storey steel frame structure shows significant reduction in floor displacement levels. 相似文献
5.
Experimental research into the seismic performance of buildings with passive oil dampers has so far been restricted to large-scale testing of frames erected on laboratory shaking tables that ignore the foundation soil below. This simplification of the problem falls short of replicating dynamic soil-structure interaction that would occur in the field. This paper presents the first experimental attempt at utilising high gravity dynamic centrifuge testing to replicate the response of a damped building at a reduced model scale. The paper compares the dynamic response of two similar two-degree-of-freedom model sway frames, one control (bare) frame and one frame equipped with miniature oil dampers, both structures founded on shallow raft foundations in dry dense sand. The miniature oil dampers successfully mitigate floor accelerations, drifts, and storey shear forces in the damped frame with minor modification to the frame stiffness. For strong, near resonance motions, global rocking of the undamped frame associated with physical uplifting of the foundation from the soil surface and subsequent yielding of sand beneath has led to floor acceleration levels, which are comparable to those obtained in the damped building fitted with miniature oil dampers. Assessment of the instrumentation installed on the miniature oil dampers reveals a viscoelastic damper behaviour with a dependency on stroke magnitude and on velocity. 相似文献
6.
Response prediction,experimental characterization and P‐spectra design of frames with viscoelastic–plastic dampers 
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下载免费PDF全文 Viscoelastic–plastic (VEP) dampers are hybrid passive damping devices that combine the advantages of viscoelastic and hysteretic damping. This paper first formulates a semi‐analytical procedure for predicting the peak response of nonlinear SDOF systems equipped with VEP dampers, which forms the basis for the generation of Performance Spectra that can then be used for direct performance assessment and optimization of VEP damped structures. This procedure is first verified against extensive nonlinear time‐history analyses based on a Kelvin viscoelastic model of the dampers, and then against a more advanced evolutionary model that is calibrated to characterization tests of VEP damper specimens built from commercially available viscoelastic damping devices, and an adjustable friction device. The results show that the proposed procedure is sufficiently accurate for predicting the response of VEP systems without iterative dynamic analysis for preliminary design purposes. A design method based on the Performance Spectra framework is then proposed for systems equipped with passive VEP dampers and is applied to enhance the seismic response of a six‐storey steel moment frame. The numerical simulation results on the damped structure confirm the use of the Performance Spectra as a convenient and accurate platform for the optimization of VEP systems, particularly during the initial design stage. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
Buildings are continually subject to dynamic loads, such as wind load, seismic ground motion, and even the load from internal utility machines. The recent trend of constructing more flexible high‐rise buildings underscores the importance of including viscoelastic dampers in building designs. Viscoelastic dampers are used to control the dynamic response of a building. If the seismic design is based only on the linear response spectrum, considerable error may occur when calculating the seismic response of a building; rubber viscoelastic dampers show non‐linear hysteretic damping that is quite different from viscous damping. This study generated a non‐linear response spectrum using a non‐linear oscillator model to simulate a building with viscoelastic dampers installed. The parameters used in the non‐linear damper model were obtained experimentally from dynamic loading tests. The results show that viscoelastic dampers effectively reduce the seismic displacement response of a structure, but transmit more seismic force to the structure, which essentially increases its seismic acceleration response. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
Dynamic responses of two buildings connected by viscoelastic dampers under bidirectional earthquake excitations 总被引：1，自引：1，他引：0
In this study,dynamic responses of two buildings connected by viscoelastic dampers under bidirectional excitations are extensively investigated.The two buildings are a 10-story building and a 16-story building,with the shorter building on the left.Viscoelastic dampers are installed at all fl oors of the shorter building.Equations of motion are formulated using a fractional derivative model to represent the viscoelastic dampers.Three cases are considered with mass eccentricities at 0,10% and-10% with respect to the dimensions of the buildings.The responses of the buildings are numerically predicted at different damper properties.The simulation results indicated that the maximum horizontal responses of the buildings without eccentricities are signifi cantly mitigated.However,torsional effects are adversely increased.For asymmetric buildings,the effectiveness of the connecting dampers is affected by building eccentricities.As a result,mass eccentricities must be taken into account in damper selection.When compared with vibrations induced by unidirectional excitations,bidirectional excitations can increase the responses of coupled asymmetric buildings.In addition,installing dampers only at the top fl oor of the shorter building may cause a sudden change in lateral stiffness of the taller building.Consequently,the story shear envelopes of the taller building are changed. 相似文献
9.
为提高装配式钢结构梁柱节点的抗震性能,首先通过熔融共混法制备高阻尼性能纳米偏高岭土/氟橡胶(NanoGmetakaolin/Fluororubber,NMK/FKM)复合材料,并对该新型材料进行4种频率下的动态力学性能试验和静态力学试验,然后以 NMK/FKM 纳米复合材料为核心耗能材料,对所提出的直角型黏弹性阻尼器进行 ABAQUS有限元模拟分析.研究结果表明:当频率为1．5Hz 时,NMK/FKM 纳米复合材料宽阻尼温域和 TA 值皆达到峰值,该工况下材料的阻尼性能最佳;直角型黏弹性阻尼器表现出刚度随位移幅值的增大而增大的动力特性;当频率为0．5、1．0和1．5Hz 时,阻尼器滞回特性表现出非线性特征,当频率升至2．0Hz时,滞回特性则为线性.随着黏弹性材料层厚度的增大,滞回环面积、阻尼器刚度和最大阻尼力逐渐减小;随着高跨比的增大,阻尼器耗能性能提升.通过调整阻尼器的高跨比和阻尼材料层厚度,可以进一步提高直角型阻尼器的动态响应. 相似文献
10.
This paper presents exact analytical solutions for a novel damped outrigger system, in which viscous dampers are vertically installed between perimeter columns and the core of a high-rise building. An improved analytical model is developed by modeling the effect of the damped outrigger as a general rotational spring acting on a Bernoulli-Euler beam. The equivalent rotational spring stiffness incorporating the combined effects of dampers and axial stiffness of perimeter columns is derived. The dynamic stiffness method(DSM) is applied to formulate the governing equation of the damped outrigger system. The accuracy and effi ciency are verifi ed in comparison with those obtained from compatibility equations and boundary equations. Parametric analysis of three non-dimensional factors is conducted to evaluate the infl uences of various factors, such as the stiffness ratio of the core to the beam, position of the damped outrigger, and the installed damping coeffi cient. Results show that the modal damping ratio is signifi cantly infl uenced by the stiffness ratio of the core to the column, and is more sensitive to damping than the position of the damped outrigger. The proposed analytical model in combination with DSM can be extended to the study of structures with more outriggers. 相似文献
11.
Viscoelastic dampers, as supplementary energy dissipation devices, have been used in building structures under seismic excitation
or wind loads. Different analytical models have been proposed to describe their dynamic force deformation characteristics.
Among these analytical models, the fractional derivative models have attracted more attention as they can capture the frequency
dependence of the material stiffness and damping properties observed from tests very well. In this paper, a Fourier-transform-based
technique is presented to obtain the fractional unit impulse function and the response of structures with added viscoelastic
dampers whose force-deformation relationship is described by a fractional derivative model. Then, a Duhamel integral-type
expression is suggested for the response analysis of a fractional damped dynamic system subjected to deterministic or random
excitation. Through numerical verification, it is shown that viscoelastic dampers are effective in reducing structural responses
over a wide frequency range, and the proposed schemes can be used to accurately predict the stochastic seismic response of
structures with added viscoelastic dampers described by a Kelvin model with fractional derivative. 相似文献
12.
A series of large‐scale dynamic tests was conducted on a passively controlled five‐story steel building on the E‐Defense shaking table facility in Japan to accumulate knowledge of realistic seismic behavior of passively controlled structures. The specimen was tested by repeatedly inserting and replacing each of four damper types, that is, the buckling restrained braces, viscous dampers, oil dampers, and viscoelastic dampers. Finally, the bare steel moment frame was tested after removing all dampers. A variety of excitations was applied to the specimen, including white noise, various levels of seismic motion, and shaker excitation. System identification was implemented to extract dynamic properties of the specimen from the recorded floor acceleration data. Damping characteristics of the specimen were identified. In addition, simplified estimations of the supplemental damping ratios provided by added dampers were presented to provide insight into understanding the damping characteristics of the specimen. It is shown that damping ratios for the specimen equipped with velocity‐dependent dampers decreased obviously with the increasing order of modes, exhibiting frequency dependency. Damping ratios for the specimen equipped with oil and viscoelastic dampers remained constant regardless of vibration amplitudes, whereas those for the specimen equipped with viscous dampers increased obviously with an increase in vibration amplitudes because of the viscosity nonlinearity of the dampers. In very small‐amplitude vibrations, viscous and oil dampers provided much lower supplemental damping than the standard, whereas viscoelastic dampers could be very efficient. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
Shear‐type buildings with Maxwell model‐based brace–damper systems are studied in this paper with a primary emphasis on the effects of brace stiffness. A single‐story building with a viscous damper installed on top of a Chevron‐brace is first investigated. Closed‐form solutions are derived for the simple structure, relating the brace stiffness and damper coefficient to the targeted reduction in response displacement or acceleration. For a given brace stiffness, the solution is minimized to give a set of formulae that will allow the optimal damper coefficient to be determined, assuring the desired performance. The model is subsequently extended to multistory buildings with viscous dampers installed on top of Chevron‐braces. For a targeted reduction in the mean square of the interstory drift, floor acceleration or base shear force, the minimum brace stiffness and optimal damper coefficients are obtained through an iterative procedure. The response reduction, which signifies the improved performance, is achieved by a combination of brace stiffness and viscous damper coefficients, unlike conventional approaches where damper coefficients are typically optimized independent of brace stiffnesses. Characteristics of multi‐degree‐of‐freedom systems are studied using a 2‐story and a 10‐story buildings where the effects of brace stiffness on the overall performance of the building can be quantified. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
This work introduces a geometric formalism, based on the use of phasors in the Argand-Gauss plane for the design and sizing of inertial dampers to be applied to multimodal structural oscillators. Their damping effect depends on the fact that the response of the secondary oscillator (the damper) delays the response of the primary mass to be controlled by 90°, so that the elastic force transmitted by the damper becomes a viscous force on the controlled oscillator. When such condition occurs we say that the damper is ‘tuned’ to the main oscillator; the damping induced by the damper is modest and serves only to limit the displacement of main oscillator.Our geometrical approach provides a method whose language is close to that of structural mechanics, thus paving the way to the professional for: (i) sizing the damper parameters; and (ii) evaluating the stability to the damped system and its performance limits. The aim of the development is explore the use of dampers to control the initial response modes of buildings under horizontal seismic and aerodynamic loads. Having introduced the concept of a monomass oscillator equivalent to a given mode of vibration, we develop a multimodal multidamper model which we then use to perform numerical evaluations. Several control strategies (involving changes in number and position of the dampers) are considered in relation to variation in bandwidth and intensity of the external forcing action. We discuss the advantages and limitations of this passive approach to structural control. 相似文献
15.
R. W. Traill-Nash 《地震工程与结构动力学》1981,9(2):153-169
When damping in a system is both significantly high and its distribution is non-classical the solution of dynamical problems by conventional modal analysis is complicated by the presence of coupling between the normal co-ordinates. Further, the convergence of a solution may be erratic with successive modal additions, leading to the need to include a larger number of modes than would otherwise be expected. In this paper methods of modal analysis in structural dynamics are discussed and their derivations briefly given. These include the conventional mode displacement method and the force summation method, employing normal modes, and the analogous procedures with damped modes. In the latter, dynamic response equations are not coupled. Dynamic loading solutions by the four approaches, each taking account of the non-classical damping distribution, are demonstrated with a simple model representing a structure on a compliant foundation. The results strongly suggest that the use of damped modes with force summation could be the most effective procedure when damping is non-classical. 相似文献
16.
结构附加粘滞阻尼器的抗震设计 总被引：2，自引：0，他引：2
本文结合抗震设计规范反应谱,给出了一个附加非线性流体粘滞阻尼器结构的抗震设计方法。研究了非线性阻尼器的力学特性,引入了非线性流体阻尼器的等效线性阻尼比,给出了计算最大加速度时刻附加非线性流体阻尼器结构反应的荷载组合系数,提出了按阻尼力的水平力分量与楼层剪力成正比的原则分配阻尼器阻尼系数的方法。同时给出了基于抗震规范设计反应谱附加非线性阻尼器结构的设计流程,通过一个算例说明了使用该方法设计附加非线性粘滞阻尼器结构的全过程。算例分析表明,这种设计方法适合于手算,便于设计人员掌握,在初步设计阶段可以快速、有效地设计满足给定性能水平的附加非线性流体阻尼器体系。 相似文献
17.
Investigated is the accuracy in estimating the response of asymmetric one‐storey systems with non‐linear viscoelastic (VE) dampers by analysing the corresponding linear viscous system wherein all non‐linear VE dampers are replaced by their energy‐equivalent linear viscous dampers. The response of the corresponding linear viscous system is determined by response history analysis (RHA) and by response spectrum analysis (RSA) extended for non‐classically damped systems. The flexible and stiff edge deformations and plan rotation of the corresponding linear viscous system determined by the extended RSA procedure is shown to be sufficiently accurate for design applications with errors generally between 10 and 20%. Although similar accuracy is also shown for the ‘pseudo‐velocity’ of non‐linear VE dampers, the peak force of the non‐linear VE damper cannot be estimated directly from the peak damper force of the corresponding linear viscous system. A simple correction for damper force is proposed and shown to be accurate (with errors not exceeding 15%). For practical applications, an iterative linear analysis procedure is developed for determining the amplitude‐ and frequency‐dependent supplemental damping properties of the corresponding linear viscous system and for estimating the response of asymmetric one‐storey systems with non‐linear VE dampers from the earthquake design (or response) spectrum. Finally, a procedure is developed for designing non‐linear supplemental damping systems that satisfy given design criteria for a given design spectrum. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
18.
Emrah Erduran 《地震工程与结构动力学》2012,41(14):1905-1919
The effects of Rayleigh damping model on the engineering demand parameters of two steel moment‐resisting frame buildings were evaluated. Two‐dimensional models of the buildings were created and response history analysis were conducted for three different hazard levels. The response history analysis results indicate that mass‐proportional damping leads to high damping forces compared with restoring forces and may lead to overestimation of floor acceleration demands for both buildings. Stiffness‐proportional damping, on the other hand, is observed to suppress the higher‐mode effects in the nine‐story building resulting in lower story drift demands in the upper floors compared with other damping models. Rayleigh damping models, which combine mass‐proportional and stiffness‐proportional components, that are anchored at reduced modal frequencies lead to reasonable damping forces and floor acceleration demands for both buildings and does not suppress higher‐mode effects in the nine‐story building. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
针对现有附加有效阻尼比计算方法存在的问题,本文从能量的角度揭示了阻尼比对结构影响的机理。从结构设计的角度,提出一种在时程分析下基于楼层剪力的消能减震结构等效阻尼比计算方法。对布置黏滞阻尼器和软钢阻尼器的消能减震模型,采用本文提出的等效阻尼比计算方法,建立等效结构进行结构响应对比。结果表明,由该计算方法得到的等效阻尼比能够准确地评估阻尼器在结构中的耗能效果,建立的等效结构能够准确反映消能减震结构实际情况。基于楼层剪力的等效阻尼比计算方法通过等效结构楼层剪力大于或等于消能减震结构楼层剪力判断迭代完成,该方法计算过程不涉及阻尼器参数及结构形式,适用于所有阻尼器类型与结构类型。计算得到的等效结构进行设计能够确保结构设计的安全。 相似文献
20.
Vibration control systems are being used increasingly worldwide to provide enhanced seismic protection for new and retrofitted buildings. This paper presents a new vibration control system on the basis of a seesaw mechanism with viscoelastic dampers. The proposed vibration control system comprises three parts: brace, seesaw member, and viscoelastic dampers. In this system, only tensile force appears in bracing members. Consequently, the brace buckling problem is negligible, which enables the use of steel rods for bracing members. By introducing pre‐tension in rods, long steel rods are applicable as bracing between the seesaw members and the moment frame connections over some stories. Seesaw mechanisms can magnify the damper deformation according to the damper system configuration. In this paper, first, the magnification factor, that is, the ratio of the damper deformation to the story drift, is delivered, which includes the rod deformation. Results of a case study demonstrate that the magnification factor of the proposed system is greater than unity for some cases. Seismic response analysis is conducted for steel moment frames with the proposed vibration control system. Energy dissipation characteristics are examined using the time‐history response results of energy. The maximum story drift angle distributions and time‐history response results of displacement show that the proposed system can reduce the seismic response of the frames effectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献