外文翻译 土建

结构控制：过去，现在和未来

作者是G. W. Housner: ASCE成员, L. A. Bergman, ASCE成员, T. K. Caughey,A. G. Chassiakos, ASCE成员, R. O. Claus, S. F. Masri, ASCE成员,R. E. Skelton,' ASCE成员, T. T. Soong,S Member, ASCE, B. F. Spencer,9 Member, ASCE, and J. T. P. Yao,lO Member, ASCE

摘要：本调查论文主要包括：（1）研究人员和从业人员提供了一个简洁的出发点都希望土木工程的控制和监测，以评估目前最先进的结构;及（2）指出两者之间的链接结构的控制和控制理论等领域的异同，并指出未来的研究和应用工作有可能证明取得丰硕成果。本文由以下几个部分组成：第1节是介绍;第2节是被动能源消耗;第3节主动控制尺寸;第4节混合动力和半主动控制系统;第5节讨论了传感器的结构控制;第6节智能材料系统;第7节健康监测和损伤检测;第8条研究的需要。大量引用的文献资料在下面列出。

1 引言

1.1项目背景

由地震或风产生的振动可以通过各种手段控制，如改变硬度，质量，阻尼，或形状，并提供被动或主动的反作用力。迄今为止，一些结构控制的方法已被成功地使用，新提出的方法提供了应用程序进行扩展和提高效率的可能性。在鉴于此，它似乎是一个适当的时间对于美国结构振动控制研究小组准备简要概述这一领域，通过实验已经有多篇论文上有发表的理论和实践。尽管民用结构控制工程方面的努力才刚开始，但已经发表的论文的数量是如此之多已经超出审阅的能力要在有限的时间审查所有在美国，亚洲和欧洲的有关的文献。作为第一个步骤，一份代表作家的意见，并提供对未来研究的建议的报告正在准备，但不会尝试面面俱到在这个领域。该报告提供把注意力集中在重要方面的问题，可以作为指导文献，也可以作为对未来的研究的一块垫脚石。现在确定的是结构控制是设计新结构和改造地震与风的结构的重要组成部分。因此，公布这个调查报告中的结构控制的研究和应用是可行的，指明对未来研究的现在方向。在美国，土木工程结构控制领域的演变是迅猛的，在过去的几几十年里吸引了众多研究者注意和兴趣。虽然其根源主要是航空航天问题跟踪和指向，灵活的空间结构技术迅速转移到民用工程。与基础设施相关的问题，如保护建筑物和桥梁在地震和风作用下的极端载荷。由于姚在1972年最初的概念研究，这个领域不断走向成熟，最终1994年8月份在洛杉矶举行了第一届世界结构振动控制会议。这吸引了来自15个国家337名参与者，包括225篇涵盖各个方面的结构控制的技术论文。作为一个管理机构和未来的会议和研讨会所的赞助者，国际结构控制协会（IASC）于1994年成立，1995年ASCE成为自动控制委员会（AACC）的一员。加入像IEEE，AIAA，AICHE，和ASME这样的拥有悠久的参与控制工程的历史的类似组织。

在日本，结构控制获得一系列发展并且

目前超过20个完整的大型建筑应用了主动控制系统，主要是为了在强风期间提高乘员舒适度，有关工作也有在欧洲和俄罗斯展开。在美国和其他地方，被动基础隔震系统在低层和中高层建筑抗震设防已经成为一种公认的设计方案。类似一般控制文献，治理结构的文献往往代表不同的利益和观点，但都有一个共同的目标：保护它们的城市和人民。 最近的在1994年，加利福尼亚州的北岭破坏性地震事件和在1995年在日本神户证明了在设计新的结构时减轻这些危险重要性。此外，应抗震设计规范要求的改变，因为一个破坏性地震，或许应该归功于最近洛杉矶市中心附近下面发现的一个活跃故障证明了分析和结构抗震性能的升级是必要的。单独的强度设计并不一定保证该建筑物维持对居住者的舒适性和安全性的动态响应。在1989年的Loma Prieta地震中，在旧金山的一幢高47层的建筑物经历了在地下室lO％g和顶层45％g的峰值加速度。表明了有害的加速度可以造成很大的地面加速度。类似的这种结构变动的事例同样发生在最近的北岭和神户地震。事实上，这种要求在强度和安全上是相互冲突的。因此增加机构的备用抵抗力的同时保持装置理想的动态特性，基于使用各种主动，半主动，被动和混合控制方案，提供了保障。目前的结构控制概念其历史可以追溯到100年以前的约翰·米尔恩，在日本的一位教授级高级工程师，他建立了一个小木屋里并将其放置在球轴承来证明结构可以避免地震晃动的影响。线性系统的理论及其应用到振动领域，并应用到特定的结构动力学，要比二十世纪的前半叶需要更多的发展。许多这方面的发展的起源于用于汽车和飞机的内燃机，本身达到非常高的动力水平。在第二次世界战争中，如隔振，减振，减振等概念得到了开发并且有效地应用于飞机结构。工程结构领域第一次接受了这一

技术是在20世纪60年代，从那时起，已经采取了若干不同的方案，一个例子是低层的基础隔震和中高层结构和桥梁。目的是较为灵活的安装在的基础结构上，依据高频率的地面运动和延长至约2秒的振动的固有周期。但是，在地震谱上在2-s周期附近明显的能量反应证明这是不理想的。另一种方法是基础隔震，其软化的固有周期是3s或4 s，但是这将导致大幅度的运动，那将是令人满意的。另外，在最近的地震速度大脉冲已被记录在该近断层区域，这也可能使普通基础隔震不切实际的。某些结构，因为它们的形状，例如修长的高层建筑，可能不适合用基础隔震。隔离器，其作用是过滤掉地面运动中的更高的频率。已被用在医院的设施中用来保护脆弱的计算机设施。这项技术已欣然接受并应用在美国的几十个新的或正在改装的隔震结构中。

对于柔性结构例如高层建筑来说，特别是那些易受强风吹袭的，辅助阻尼器成功的发挥了作用。减震装置，无论是粘性的，粘弹性、或塑料的，整个结构被部署在结构中提供了一个显著的增加能量耗散和减少震动的作用。目前建筑中采用辅助阻尼器的包括在纽约市的世界贸易中心大厦和在西雅图和加州的几栋建筑。 另一种被动的方法是被应用到更高的建筑上以减少风引起的振动的是调谐质量阻尼器（TMD）。这个装置是一个经典的动力吸振器，组成的辅助的质量占总的结构质量的1％，设置于建筑物的顶部，并通过一个无源的弹簧与阻尼器连接。辅助系统被调谐，以减少建筑运动的振幅。虽然这是一种特别有效的方法去固定窄带运动，但是它并不适用于瞬态效应占主导地位的运动，如激烈的地震。然而，设计者已经掌握了几个参数，包括质量比和吸收器的阻尼比，应该与装置的频率和衰减能力是有关的。自从20世纪70年代TMDs已在美国得到应用，

这样的例子你可以在波士顿的约翰汉考克大厦和在纽约的花旗集团大厦得到证明。

正如在前言中提到的第一届结构控制世界大会上指出的，结构控制具有

鲜明的特点并且给这个领域的研究指明了方向。这些功能是卓越的。

首先，土木工程结构锚固的，因此是处于静态稳定的。在部署时单纯的

提高主动控制增大了它的不稳定的可能性，相反，空间结构需要主动控制的稳定性。此外， 众所周知，土木结构所受到环境的干扰，例如风和地震，是非常不确定的，取决于它们的大小和到达的时间这个特点，而机械载荷的要求是有据可查的。此外，土木工程结构通常的性能要求通常是比较粗略的相比飞机和航天器对结构的性能要求。它们的性能要求通常只有比较细微的不同。 那些已经使用在已建成的建筑物及桥梁上的结构控制表明，这是一个宝贵的工程工具。并且，此外，可能的组合方法和更复杂的方法，在长时间的使用过程中已经得到了充分的保障。事实上，在土木工程结构振动控制领域，现在似乎发展成一种特别的科目涵盖了大体积和大规模结构的振动问题，涉及到通过多种方法给结构施加反作用力来改变它的振动特性进而控制其运动。在目前的发展阶段这种方法比较理想的总结了这个技术领域的状态，并指出了未来研究发展方向。 1.2国际发展

美国国家结构振动控制研讨会于1990年在由美国国家委员会的资助的

美国国家科学基金会（NSF）的主持下在美国南加州大学召开，吸引了近100位 参与着，其中包括来自加拿大 中国，德国，意大利，日本，墨西哥和西班牙的几位代表。

STRUCTURAL CONTROL: PAST, PRESENT, AND FUTURE

By G. W. Housner: Member, ASCE, L. A. Bergman,z Member, ASCE, T. K. Caughey,3

A. G. Chassiakos,4 Member, ASCE, R. O. Claus,s S. F. Masri,6 Member, ASCE, R. E. Skelton,' Member, ASCE, T. T. Soong,S Member, ASCE,

B. F. Spencer,9 Member, ASCE, and J. T. P. Yao,lO Member, ASCE

ABSTRACT: This tutoriaVsurvey paper: (1) provides a concise point of departure for researchers and practitioners

alike wishing to assess the current state of the art in the control and monitoring of civil engineering

structures; and (2) provides a link between structural control and other fields of control theory, pointing out both

differences and similarities, and points out where future research and application efforts are likely to prove fruitful. The paper consists of the following sections: section 1 is an introduction; section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control

systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section

7 deals with health monitoring and damage detection; and section 8 deals with

research needs. An extensive list

of references is provided in the references section. 1 INTRODUCTION 1.1 Background

The control of structural vibrations produced by earthquake or wind can be done by various means such as modifying

rigidities, masses, damping, or shape, and by providing passive or active counter forces. To date, some methods of structural control have been used successfully and newly proposed methods offer the possibility of extending applications and improving efficiency. In view of this, it seems an appropriate time for the U.S. Panel on Structural Control Research to prepare a summary overview of the field, as many papers have been published on the theory and practice as well as on experiment and performance. Although work on structural control in civil engineering is relatively recent, the number of papers published is so large that it is beyond the capability of the panel

to review all relevant literature in the United States, and in Asia and Europe in a limited time. As a first step, a report was prepared that represents the views of the writers and provides recommendations for future research, but does not attempt to cover everything published in the field. Such a report serves to focus attention on important aspects of the subject, can be a guide to the literature, and can also serve as a stepping stone for future reports. It is now established that structural control

'Prof. Emeritus, Div. of Engrg. and App!. Sci., California Inst. of Technol., Pasadena, CA 91125.

'Prof., Dept. of Aeronautical and Astronautical Engrg., Coli. of Engrg., Univ. of I1linois at Urbana-Champaign, Urbana, IL 61801.

'Prof., Div. of Engrg. and App!. Sci., California Inst. of Techno!., Pasadena, CA.

4Prof., Coli. of Engrg., California State Univ., Long Beach, CA 90840. 'Prof., Dept. of Electr. Engrg., Coli. of Engrg. Virginia Polytechnic Inst. & State Univ., Blacksburg, VA 24061.

\Southern California, Los Angeles, CA 90089.

?Prof., Dept. of App!. Mech. and Engrg. Sci., Univ. of California, San Diego, San Diego, CA 92037.

\Univ. of New York at Buffalo, Buffalo, NY 14222.

\Univ., Notre Dame, IN 46556.

'''Prof., Dept. of Civ. Engrg., Texas A&M Univ., College Station, TX 77843.

Note. Associate Editor: Sami Masri. Discussion open until February I, 1998. To extend the closing date one month, a written request must be filed with the ASCE Manager of Journals. The manuscript for this paper was submitted for review and possible publication on May 29, 1997. This paper is part of the Journal of Engineering Mechanics, Vol. 123, No.9, September, 1997. ?ASCE, ISSN 0733-9399/97/0009-08970971/$ 4.00 + $.50 per page. Paper No. 15617.

can be an important part of designing new structures and retrofitting existing structures for earthquake and wind. Therefore, it seems desirable to issue this survey of publications of

structural control research and applications, and to present directions for future research.

In the United States, the evolution of the civil engineering

field of structural control has been rapid, attracting the interest and attention of scores of researchers over the past several

decades. Though having its roots primarily in such aerospacerelated problems as tracking and pointing, and in flexible space

structures, the technology quickly moved into civil engineering and infrastructure-related issues, such as the protection of buildings and bridges from extreme loads of earthquakes and winds. Since the initial conceptual study by Yao in 1972, the field has continued to mature, culminating in the First World Conference on Structural Control, held in Los Angeles in August 1994. This attracted 337 participants from 15 countries,

and 225 technical papers covering various aspects of structural

control were presented. The formation of the International Association for Structural Control (IASC) as a governing body

and sponsor of future conferences and workshops took place in 1994. ASCE became a member of the American Automatic

Control Council (AACC) in 1995, joining such peer organizations as the IEEE, AIAA, AIChE, and ASME who have a

long history of involvement in controls engineering. Furthermore, in Japan, structural control has developed in parallel and more than 20 full-scale buildings are currently implemented with active control systems, primarily to enhance occupant comfort during periods of high winds; relevant work has also been carried out in Europe and Russia. In the United States

and elsewhere, passive base isolation systems in low- and medium- rise buildings for seismic protection have become an accepted design strategy. Similar to the general controls literature, the structural control literature tends to represent diverse interests and viewpoints, though all share a common goal: the protection of cities and the people in them.

Recent destructive seismic events in Northridge, California

in 1994 and Kobe, Japan in 1995 demonstrated the importance of mitigating these hazards in the design of new structures. Also, should seismic code requirements change because of a destructive earthquake, or due to discovery of a nearby active fault as recently identified beneath downtown Los Angeles, reanalysis and upgrading of seismic resistance of structures will be required.

Design for strength alone does not necessarily ensure that the building will respond dynamically in such a way that the comfort and safety of the occupants is maintained. For ex- JOURNAL OF ENGINEERING MECHANICS / SEPTEMBER 1997/897 J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved.

ample, during the 1989 Loma Prieta earthquake, a 47-story building in San Francisco experienced peak accelerations of about lO%g in the basement and 45%g on the top floor, which indicates that harmful accelerations in the upper stories can result from strong ground accelerations. Similar comments can be made regarding the behavior of structures during the recent Northridge and Kobe earthquakes. In fact, the requirements

for strength and for safety can be conflicting. Thus, alternate means of increasing the resistance of a structure while maintaining desirable dynamic properties, based on the use of various active, semiactive, passive, and hybrid control schemes, offers great promise.

The notion of structural control as currently defined can trace its roots back more than 100 years to John Milne, a professor of engineering in Japan, who built a small house of wood and placed it on ball bearings to demonstrate that a

structure could be isolated from earthquake shaking. The development of linear system theory and its application to the

field of vibration, and in particular structural dynamics, required much of the first half of the twentieth century. The

driving force for much of this development was the internal combustion engine, used in both automobiles and airplanes, which inherently produced significant dynamic force levels at connection points. It was during the second world war that

concepts such as vibration isolation, vibration absorption, and vibration damping were developed and effectively applied to aircraft structures.

The structural engineering community first embraced this technology in the 1960s, and since then has pursued a number of different paths; one example is base isolation for low-rise

and medium-rise structures and bridges. The objective is to

mount the structure on a sufficiently flexible base that filters out the high frequencies of the ground motion and lengthens the natural period of vibration to approximately 2 s. However, this would be unsatisfactory if the earthquake spectrum had a significant amount of energy in the neighborhood of a 2-s period. The alternative would be to soften the base isolation until the natural period was 3 or 4 s, but this would lead to large amplitude motions that would be objectionable. Also, in recent earthquakes a large velocity pulse has been recorded in the

near-fault region and this may also make ordinary base isolation impractical. Certain structures because of their shape,

for example slender high-rise buildings, may not be suitable

for base isolation. Isolators, whose purpose is to filter out the higher frequencies in the ground motion, have been used to

protect the fragile contents of hospitals, computer facilities, and so on. This technology had been readily accepted and

several dozen base-isolated structures, new or retrofitted, are currently in use or under construction in the United States. For flexible structures such as tall buildings, particularly those susceptible to strong winds, auxiliary dampers have been successfully employed. The damping devices, either viscous, viscoelastic, or plastic are deployed throughout the structure,

providing a significant increase in energy dissipation and reduction of motion. Buildings currently employing auxiliary

dampers include the World Trade Center in New York City and several buildings in Seattle and in California.

Another passive approach applied to taller buildings to reduce wind induced vibrations is the tuned mass damper

(TMD). This device is a classical dynamic vibration absorber, consisting of an auxiliary mass on the order of 1% of the mass of the total structure, located at the top of the building and connected through a passive spring and damper. The auxiliary system is tuned to reduce the amplitude of building motion. While this is a particularly effective strategy for stationary, narrow band motions, it is less so for broadband excitations such as earthquakes, where transient effects are dominant. However, the designer has several parameters, including mass 898/ JOURNAL OF ENGINEERING MECHANICS / SEPTEMBER 1997 ratio and absorber damping ratio, with which the bandwidth and attenuation capability of the device can be controlled. TMDs have been employed in the United States since the 1970's; examples can be found in the John Hancock Tower in Boston and in the Citicorp Building in New York City.

As pointed out in the foreword to the proceedings of the

First World Conference on Structural Control, \control has distinctive features that govern the direction of research\First, civil engineering structures are anchored and, thus,

are statically stable. The addition of purely active control carries with it the possibility of destabilization and is thus suspect. This is in contrast to space structures which, when deployed,

require active control for stability. Further, environmental disturbances that we associate with civil engineering structures,

for example wind and earthquakes, are highly uncertain with

respect to magnitude and arrival times, while the characteristics of mechanical loads are fairly well documented. Also, performance requirements that we associate with civil engineering

structures are generally coarse by comparison with those of,

say, aircraft and spacecraft. These are but a few of the differences. The buildings and bridges that have been constructed using structural control show that it is a valuable engineering tool and, in addition, possible combinations of methods and more sophisticated methods show promise of extended use. In fact,

structural control in civil engineering seems now to be developing into a special form of vibration problem involving large and massive bodies whose motions are to be controlled by modifying the vibrational properties in a variety of ways or by applying counterforces. At the present stage of development it is desirable to summarize the state of the art and to point the way to future developments. 1.2 Recent International Developments

The U.S. National Workshop on Structural Control, held at

the University of Southern California in 1990 under the auspices of the National Science Foundation (NSF) sponsored

U.S. National Panel on Structural Control, attracted nearly 100 participants, including several representatives from Canada, China, Germany, Italy, Japan, Mexico, and Spain. This was followed by several additional meetings, including the Japan National Workshop, the U.S.-Italy Workshop in 1992, and an international workshop held in Hawaii in 1993. Perhaps the

most significant event took place at the Tenth World Conference on Earthquake Engineering in Madrid, Spain in 1992,

which saw several technical sessions dedicated to topics in structural control. Here, the decision to form an international association and to hold a world conference dedicated to structural control was made. The IASC was formed the next year,

with Professor G. Housner as president, Professor T. Kobori

as vice president, and Professor S. Masri as secretary-treasurer. Their efforts led to the successful First World Conference, where 337 participants from 15 countries met to present and

discuss the results of their research. Additional activity in the field also took place at various international meetings, several of which held special symposia and theme sessions devoted to structural control. These included both the 10th and 11 th World Conferences on Earthquake Engineering, held in Madrid and in Acapulco, respectively. Most recently, the

First European Conference on Structural Control was successfully held in Barcelona, Spain, attracting more than 100 international participants. The Second International Workshop

on Structural Control, which was held in Hong Kong in December of 1996, attracted the participation of 85 scientists and engineers from 10 countries. The forthcoming Second World Conference, to be held in Tokyo in 1998, promises to J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved.

extend the frontiers of this exciting new area of civil engineering. 1.3 Scope

The motivation behind this tutoriaVsurvey paper is twofold. First, it is meant to provide a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control of civil engineering structures. Second, and perhaps more important, it provides a link between structural control and other fields of control theory,

pointing out both differences and similarities and where future research and application efforts are likely to prove fruitful. The paper is organized in the following way: section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control

systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals

with research needs. An extensive list of references is provided in the references section.

Given the very broad and interdisciplinary nature of the field

of structural control and monitoring of civil infrastructure systems, it is not feasible to discuss or cite all relevant publications and applications. The writers have done their best to

present a balanced view of the developments in the field of structural control and monitoring, however, only a limited number of references could be cited. Consequently, absence of

a citation of a particular work should not be construed as implying anything about the publication's merit. Where appropriate,

publications in technical journals were preferred for inclusion over related publications in proceedings. Also, when

discussing control theory, emphasis was placed on those issues related to the physical behavior of civil structures as opposed to sophisticated developments in control system theory. 1.4 Definitions

For convenience, definitions of some key terms will be provided.

1.4.1 Active Control An active control system is one in which an external source

powers control actuator(s) that apply forces to the structure in a prescribed manner. These forces can be used to both add and dissipate energy in the structure. In an active feedback control system, the signals sent to the control actuators are a function of the response of the system measured with physical sensors (optical, mechanical, electrical, chemical, and so on).

1.4.2 Passive Control A passive control system does not require an external power

source. Passive control devices impart forces that are developed in response to the motion of the structure. The energy in

a passively controlled structural system, including the passive devices, cannot be increased by the passive control devices.

1.4.3 Hybrid Control The common usage of the term \

the combined use of active and passive control systems. For example, a structure equipped with distributed viscoelastic damping supplemented with an active mass damper on or near

the top of the structure, or a base isolated structure with actuators actively controlled to enhance performance.

1.4.4 Semiactive Control Semiactive control systems are a class of active control systems for which the external energy requirements are orders of

magnitude smaller than typical active control systems. Typically, semiactive control devices do not add mechanical energy

to the structural system (including the structure and the control actuators), therefore bounded-input bounded-output stability is guaranteed. Semiactive control devices are often viewed as controllable passive devices.

1.4.5 Structural Health Monitoring Health monitoring refers to the use of in-situ, nondestructive sensing and analysis of structural characteristics, including the structural response, for the purpose of detecting changes that may indicate damage or degradation.

2 PASSIVE ENERGY DISSIPATION

All vibrating structures dissipate energy due to internal

stressing, rubbing, cracking, plastic deformations, and so on;

the larger the energy dissipation capacity the smaller the amplitudes of vibration. Some structures have very low damping

on the order of 1% of critical damping and consequently experience large amplitudes of vibration even for moderately

strong earthquakes. Methods of increasing the energy dissipation capacity are very effective in reducing the amplitudes of vibration. Many different methods of increasing damping have been utilized and many others have been proposed. Passive energy dissipation systems encompass a range of materials and devices for enhancing damping, stiffness and strength, and can be used both for natural hazard mitigation

and for rehabilitation of aging or deficient structures. In recent years, serious efforts have been undertaken to develop the concept of energy dissipation or supplemental damping into a

workable technology and a number of these devices have been

installed in structures throughout the world (Soong and Constantinou 1994; Soong and Dargush 1997). In general, they

are all characterized by a capability to enhance energy dissipation in the structural systems to which they are installed.

This may be achieved either by conversion of kinetic energy to heat, or by transferring of energy among vibrating modes. The first method includes devices that operate on principles

such as frictional sliding, yielding of metals, phase transformation in metals, deformation of viscoelastic solids or fluids, and fluid orificing. The latter method includes supplemental oscillators, which act as dynamic vibration absorbers.

In what follows, advances in this area in terms of research,

development of design guidelines, and implementation as documented in recent publications are presented and discussed. 2.1 Metallic Yield Dampers

One of the effective mechanisms available for the dissipation of energy input to a structure from an earthquake is

through inelastic deformation of metals. The idea of utilizing added metallic energy dissipators within a structure to absorb a large portion of the seismic energy began with the conceptual and experimental work of Kelly et al. (1972) and Skinner et

al. (1975). Several of the devices considered included torsional beams, flexural beams, and V-strip energy dissipators. During the ensuing years, a wide variety of such devices has been proposed (Bergman and Goel 1987; Whittaker et al. 1991; Tsai et al. 1993). Many of these devices use mild steel plates with

triangular or hourglass shapes so that yielding is spread almost uniformly throughout the material. A typical X-shaped plate damper or added damping and stiffness (ADAS) device is shown in Fig. 1. Force-displacement response of an ADAS

device under constant amplitude displacement controlled cycles has been examined by Whittaker et al. (1991). A typical

result is displayed in Fig. 2, where the area within the hysteresis loops measures the amount of dissipated energy. Other JOURNAL OF ENGINEERING MECHANICS / SEPTEMBER 1997/899 J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved. 2 0.' 2

0.0 0.2 0??

Dlapl8cernent (Inch) ·1 0 1

Dlapl8C8l1len1 (Inch) ~.2 ·1 0

Dlapl8C8111enl (Inch) ·2

TMI 880706.17 TMI 880706.16 T..1880706.06 --_._-~~--~_._.- ./ ·10 ·11 ~.. (a) 1. 10 i ~ I ~ 0 0 I.I.. J .. III ·10 ·11 ·2 (b) 11

10 i ~ I ~ 0

{..l ., JIII ·10 .11-3 (e) 11 i 10 ~ I

materials, such as lead and shape-memory alloys, have been evaluated (Sakurai et aI. 1992; Aiken and Kelly 1992). Some

particularly desirable features of these devices are their stable

hysteretic behavior, low-cycle fatigue property, long-term reliability, and relative insensitivity to environmental temperature. Hence, numerous analytical and experimental investigations have been conducted to determine these characteristics in individual devices.

Despite obvious differences in their geometric configuration, the underlying dissipative mechanism in all cases results

from inelastic deformation of the metallic elements. Therefore, to effectively include these devices in the design of an actual

structure, one must be able to characterize their expected hysteretic behavior under arbitrary cyclic loading. Ideally, one

would hope to develop a model of any metallic device starting from the micromechanical theory of dislocations, which must ultimately determine its inelastic response. However, since a

direct physical approach from first principles is not yet feasible, one normally accepts a phenomenological description

based on observation of behavior at the macroscopic level. A mathematically consistent framework, such as plasticity or

viscoplasticity theory, is then constructed to reproduce that behavior and to predict response under general conditions (Ozdemir 1976; Bhatti et aI. 1978). This approach may reduce the requirements for component testing. Recently, Dargush and FIG. 2. Force Displacement Response of ADAS Device (Whittaker et al. 1991)-Dlsplacement AmplitUde: (a) 0.45 In.; (b) 1.5 In.; (c) 2.2 In. T 2.00 ! 2.00 5.00 ~1.25-+1

o (b) o

~1.25--1 t 0 0 t1.00 ..:L

~ 5.00 -I (a)

I· 7.75 -I I· 5.75 -I

- - -- -- ----- - - -- - I -- ~- - -.- t o.125 ~ 1-0.25 It- 2.00--1

r- - -- - - -- .- - - - -- - - -- .- - '-- -

FIG. 1. X-Shaped ADAS Device (Whittaker et al. 1991) 900 I JOURNAL OF ENGINEERING MECHANICS I SEPTEMBER 1997 J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved.

- Numerical Results

700........--------.......--------, 700.

parameters, and determined ultimate displacements of the devices with various sizes based on experimental data obtained

from the hysteretic behavior and low-cycle fatigue property testing of about 100 devices.

To utilize metallic dampers within a structural system, it is necessary to formulate design guidelines and procedures based on knowledge gained from theoretical and experimental studies. Since all metallic yield dampers are nonlinear devices, a linear system with such devices will become nonlinear. Some research has been conducted in an effort to establish design methodologies for metallic energy dissipation systems by putting the hysteretic force-displacement model of metallic devices in the equation of motion of the structure to be designed.

Response analysis under all intensity levels of earthquakes can then be conducted and, on the basis of analytical results, a design methodology for structures with metallic devices may be established (Xia et aJ. 1990; Xia and Hanson 1992; Tsai et al. 1993; Pong et aJ. 1994). Their analytical results show that,

for X-shaped and triangular plate elements, parameters BID (ratio of bracing stiffness to device stiffness), SR (brace-device assemblage stiffness to that of corresponding structural story), and Xy (yielding displacement of the device) are key parameters in reducing seismic response. An alternative design procedure based on the concept of equivalent viscous damping

corresponding to metallic devices was outlined in Scholl

(1993) and is used in the ongoing efforts to establish building code requirements for passive energy dissipation systems (Whittaker et aJ. 1993).

The earliest applications of metallic yield dampers to structural systems occurred in New Zealand (Skinner et a1. 1980). Recently, ADAS devices have been installed in a 29-story

steel-frame building in Naples, Italy (Ciampi 1991), in a twostory nonductile reinforced concrete building in San Francisco

as a part of seismic retrofit (Perry et a1. 1993), and in three reinforced concrete buildings in Mexico City, also as a part of seismic retrofit (Martinez-Romero 1993). In Japan, lead extrusion devices and other metallic yield dampers have been installed in a number of buildings. 2.2 Friction Dampers

Friction provides another excellent mechanism for energy dissipation, and has been used for many years in automotive

brakes to dissipate kinetic energy of motion. In structural engineering, a wide variety of devices have been proposed and

developed, differing in mechanical complexity and sliding materials. In the development of friction dampers, it is important

to minimize stick-slip phenomena to avoid introducing highfrequency excitation. Furthermore, compatible materials must

be employed to maintain a consistent coefficient of friction over the intended life of the device.

The Pall device (Fig. 4) is one of these damper elements

utilizing the friction principle, which can be installed in a

structure in an X-braced frame as illustrated in this figure (Pall and Marsh 1982). Force-displacement responses of the Pall dampers have been studied extensively. A plot of its typical cyclic response is displayed in Fig. 5 (Filiatrault and Cherry 1987). The dampers are designed not to slip during wind

storms or moderate earthquakes. However, under severe loading conditions, the devices slip at a predetermined optimum load before yielding occurs in primary structural members.

Several earthquake simulator studies have illustrated the beneficial effects of utilizing these devices (Filiatrault and Cherry 1987, 1990; Aiken et aJ. 1988).

In the intervening years, a number of friction devices have been developed, for example, Sumitomo friction damper (Aiken and Kelly 1990), energy dissipating restraint (Nims et al.

1993a), and slotted bolted connection energy dissipator (FitzGerald et a1. 1989; Grigorian et aJ. 1993). Typically, these JOURNAL OF ENGINEERING MECHANICS / SEPTEMBER 1997/901 0.36 0.360 O. 350.

-700+----.....--~~==...;..;.;:\-0.36 -350 -700.

-1050H-----,---r----.--........---r---l -0.360 -0.240 -0.120 0.000 0.120 0.240 Deformation Angle (y= AI L) 350 Z~

-w 0 (,) a:

0u. Py - - -350 Pp - - (8) -z ~-w~ ou. (b)

1050.\

FIG. 3. Hysteresis of Triangular Plate Metallic Damper: (a) Experimental (Tsai et al. 1993); (b) Numerical (Dargush and Soong 1995)

Soong (1995) developed an inelastic constitutive model for the material of metallic yield dampers based on a microscopic

mechanistic approach and made some comparison with experimental data for validation of the model, in which the experimental and numerical results of the hysteretic behavior of

a triangular plate metallic damper are shown in Fig. 3. Tsai and Tsai (1995) developed a finite-element formulation for the tapered-plate energy dissipator, and compared it with experimental data, showing that the proposed model effectively predicts the device behavior under wind and earthquake loading. In the development of suitable hysteretic models, there is

an alternative approach, which involves the direct use of experimental data obtained from component testing of the device.

In this approach, the basic form of the hysteretic model

is first selected, and then the model parameters are determined or the relationships between the model parameters and the size and material parameters of the device are established via a curve fitting procedure or some macroscopic mechanical analysis of the device. In using this approach, any appropriate

hysteretic restoring forcing model, such as a bilinear one, suitable for the metal elements may be selected to describe hysteretic behavior of the devices. Ou and Wu (1995), by employing a bilinear model to describe the hysteretic behavior of

X-shaped and triangular plate dampers, established a relationship between the model parameters and the size and material J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved.

FIG. 4. Pall Friction Damper (Pall and Marsh 1982)

FIG. 5. Force-Displacement Response of Pall Friction Device (Flllatrault and Cherry 1987)

needed in adopting one of these models in the response analysis and design of structures with friction dampers. Additionally, long-tenn behavior and durability of these devices, particularly after long periods of inactivity, have not been adequately addressed.

After a hysteretic model is validated for a particular friction damper, it can be readily incorporated into an overall structural analysis. Although some attempts have been made to introduce the concept of equivalent viscous damping [e.g., Scholl

(1993)], in general, a full nonlinear time domain analysis is required. Recent numerical and theoretical investigations show that parameters YSR (ratio of initial slip load to yielding force of corresponding structural story) and SR (ratio of bracing

stiffness to stiffness of corresponding structural story) are the key ones in reducing seismic response (Nims et al. 1993; Scholl 1993). Comparisons made with corresponding unbraced

and conventionally braced frames indicate that friction dampers effectively reduce displacements, while maintaining comparable acceleration levels (Nims et al. 1993b). Based on nonlinear response analysis, the corresponding design procedure

for frictionally damped structures may be proposed. Filiatrault and Cherry (1990) presented a design method based on the

development of design slip-load spectra. This method does not need nonlinear analysis and may serve as a preliminary design step for the structure and its friction devices.

In recent years, there have been several applications of friction dampers aimed at providing enhanced seismic protection

of new and retrofitted structures. This activity is primarily associated with the use of Pall friction devices in Canada, and

Sumitomo friction dampers in Japan. The Pall X-braced friction devices and their variations have been installed in several buildings, some as retrofits and some new facilities (Pall and Pall 1993, 1996). Three building projects in Japan, including the 31-story steel-frame Sonic office building in Omiya City, involving Sumitomo friction dampers, are briefly described in Aiken and Kelly (1990).

A combination mechanism, which incorporates a friction

damping device for control of structural damage due to severe earthquake motion and a viscoelastic damping device for control of low energy excitation, such as wind forces or mild

ground movements, has also been a subject of recent investigations (Tsiatas and Olson 1988; Pong et al. 1994a,b; Tsiatas

and Daly 1994). This mechanism consists of a frictional slider and a viscous damper acting in series. The viscoelastic material dissipates energy induced by mild earthquakes or wind

action. Once the force exceeds a certain value, the frictional mechanism begins to dissipate energy and at the same time preserves the integrity of the damper.

In other developments, Dorka in 1992 developed a bidirectional friction device, consisting of a stack of sliders that are

alternately flat and convex, causing a nearly circular distribution of clamping pressure over the contact area. Pradlwater et al. (1994) analyzed the random response of a two-dimensional (2D) structure with bidirectional friction devices and studied

their effectiveness in response reduction. Additionally, frictional dampers have been used in the study of seismic retrofit

of reinforced concrete structures (Li and Reinhorn 1995). Experimental and analytical results show that they can reduce

inelastic defonnation demands, and moreover, reduce damage quantified by an index monitoring pennanent defonnations. 2.3 Viscoelastic Dampers

The metallic and frictional devices described are primarily intended for seismic application. On the other hand, there is a class of viscoelastic solid materials that can be used to dissipate energy at all defonnation levels. Therefore, viscoelastic

dampers can find applications in both wind and seismic protection. col.

I+t--Iinks 1000 4.45

'0.40 -0.20 0.20 0.40 (In) I!

-10.18 -5.08 5.08 (mm) ·1000 -4.45 -2000 8.90

slip Joint with

friction pad ---t--++++\(8) (b) ,; P

(1bs) (kN) No. of Cycles\

2000 8.110 Excitation Frequency. 0.20Hz

devices provide good perfonnance and their behavior is not

significantly affected by loading amplitude, frequency, or even

the number of loading cycles. The devices differ in their mechanical complexity and the materials used for the sliding surfaces. Recently, a similar type of friction device, the Tekton

friction damper, was tested (Li and Reinhorn 1995). Most friction devices utilize sliding interfaces consisting of steel on

steel, brass on steel, or graphite impregnated bronze on stainless steel. Composition of the interface is of great importance for insuring longevity of operation of the devices. Low carbon alloy steels, for example, corrode and their interface properties will change with time. Moreover, brass or bronze promotes additional corrosion when it is in contact with low carbon. Only steels with high chromium content do not appear to suffer additional corrosion in contact with brass or steel.

At present, most macroscopic hysteretic models for friction dampers are obtained from test data assumed to be Coulomb

friction with a constant coefficient of friction. Some care is 902/ JOURNAL OF ENGINEERING MECHANICS / SEPTEMBER 1997 J. Eng. Mech. 1997.123:897-971. Downloaded from ascelibrary.org by Henan University of Technology on 03/05/13. Copyright ASCE. For personal use only; all rights reserved.

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