58559土木工程专业英语鲁正电子课件-普及版energy dissipation state of the art and practice

1、Unit 13 Supplemental Energy Dissipation: State-of-the-art and State-of-the-practiceEnglish for Civil EngineeringTeacher: Prof. Zheng LuE-mail: （School of Civil Engineering, TONGJI UNIVERSITY）Unit 13 Supplemental Energy Dissipation: State-of-the-art and State-of-the-practice13.1 Introduction 综述减震构件的类

2、型13.2 Basic Principles 公式原理13.3 Passive Energy Dissipation 被动系统Metallic dampersFriction damperVE dampersViscous fluid dampersTuned mass dampers Tuned liquid dampers13.4 Active, Hybrid and Semi-active Control Systems 主动、混合、半主动系统Hybrid mass damper systemsActive mass damper systemsSemi-active damper sy

3、stemsSemi-active Controllable Fluid Dampers13.1 IntroductionIn recent years, innovative means of enhancing structural functionality and safety against natural and man-made hazards have been in various stages of research and development. By and large, they can be grouped into three broad areas as sho

4、wn in Table 13-1.1). base isolation;2). passive energy dissipation；3). active control.抵御自然和人为灾害提高结构功能和安全性的方法：三大类innovative 创新，革新；stages 阶段；by and large 大体上，总的来说；13.1 IntroductionOf the three, base isolation can now be considered a more mature technology with wider applications as compared with the o

5、ther two.Passive energy dissipation systems pass a range of materials and devices for enhancing damping, stiffness and strength, and can be used both for seismic hazard mitigation and for rehabilitation of aging or deficient structures. In general, such systems are characterized by their capability

6、to enhance energy dissipation in the structural systems in which they are installed. These devices generally operate on principles such as frictional sliding, yielding of metals, phase transformation in metals, deformation of viscoelastic (VE) solids or fluids and fluid orificing.基础隔震相对成熟和应用；被动控制包括很

7、多材料和设备（提高阻尼、刚度、强度）。同时用于减少地震灾害和修复年久破损结构。 pass ，围绕，包围； mitigation，缓解，减轻； rehabilitation，修复；dificient，有缺陷的； viscoelastic，粘弹性；orifice，孔口；on principles ，基于原理； phase transformation in metals，金属相变。13.1 IntroductionActive/hybrid/semi-active control systems are force delivery devices integrated with real-tim

8、e processing evaluators/controllers and sensors within the structure. They act simultaneously with the hazardous excitation to provide enhanced structural behavior for improved service and safety. Research to date has also reached the stage where active systems have been installed in full- scale str

9、uctures for seismic hazard mitigation. 主动、混合、半主动控制实时评估和控制传感器目前可安装在全尺结构simultaneously ，同时；research to date ，迄今为止的研究。13.1 IntroductionThis paper provides an assessment of the state-of-the-art and state-of-the-practice of this exciting, and still evolving, technology. Also, included in the discussion a

10、re some basic concepts, the types of structural control systems being used and deployed, and their advantages and limitations in the context of seismic design and retrofit of civil engineering structures.文章思路技术评估+结构控制体系的基本概念、种类、优缺点。state-of-the-art and state-of-the-practice，发展水平和实践； in the context o

11、f ，在情况下，在背景下。13.2 Basic Principles13.2 Basic PrinciplesConsider now the addition of a generic passive energy dissipation (PED) element into the SDOF model. The equation of motion for the extended SDOF model then es (schematically represented by Fig. 13-1b)m+ c+ kx+x=m+) where is the mass of the PED

12、element and the force corresponding to the device is written as x, representing a generic integrodifferential operator.The specific form of x needs to be specified before Eq. (13-2) can be analyzed, which is necessarily highly dependent on the device type. It is seen from Eq. (13-2) that the additio

13、n of the x term in Eq. (13-2) modified the structural properties so that it can respond more favorably to the designed or anticipated ground motion. 引入被动控制后公式的变化generic，通用的； integrodifferential operator，积分运算符，积分算子13.2 Basic PrinciplesAn active structural control system, on the other hand, has the ba

14、sic configuration as shown schematically in Fig. 13-1c. It consists of:1) sensors located about the structure to measure either external excitations, or structural response variables, or both.2) devices to process the measured information and to compute necessary control forces needed based on a giv

15、en control algorithm.3) actuators, usually powered by external sources, to produce the required forces.主动控制系统的组成。algorithm，算法；actuators，执行器，激励器。13.2 Basic PrinciplesWhen only the structural response variables are measured, the control configuration is referred to as feedback control since the struct

16、ural response is continually monitored and this information is used to make continual corrections to the applied control forces. A feedforward control results when the control forces are regulated only by the measured excitation, which can be achieved, for earthquake inputs, by measuring acceleratio

17、ns at the structural base. In the case where the information on both the response quantities and excitation are utilized for control design, the term feedback-feedforward control is used.句式比较繁杂。反馈控制的机理。be referred to as，被称为，视为； feedforward，前馈控制。13.2 Basic PrinciplesTo see the effect of applying such

18、 control forces to the linear structure considered above, Eq. (13-1) in this case esm+ c+ kx=mu(t) (13-3)where u(t) is the applied control force.Suppose that the feedback configuration is used in which the control force u(t) is designed to be u(t) (13-4) and Eq. (13-3) es m+ c+ kx+x=m (13-5)It is se

19、en that the effect of feedback control is again to modify the structural properties. In comparison with passive control, however, an important difference is that the form of x is now governed by the control law chosen for a given application, which can change as a function of the excitation. 主动调节的机理

20、和与被动控制的区别。13.2 Basic PrinciplesOther advantages associated with active control systems can be cited; among them are:1) enhanced effectiveness in response control; the degree of effectiveness is, by and large, only limited by the capacity of the control systems.2) relative insensitivity to site condi

21、tions and ground motion.3) applicability to multi-hazard mitigation situations; an active system can be used, for example, for motion control against both strong wind and earthquakes.4) selectivity of control objectives; one may emphasize, for example, human comfort over other aspects of structural

22、motion during noncritical times, whereas increased structural safety may be the objective during severe dynamic loading.主动控制的其他优点。cite，举例; by and large，总的来说。13.2 Basic PrinciplesIt is useful to distinguish among several types of active control systems currently being used in practice. The term hybri

23、d control generally refers to a combined passive and active control system as depicted in Fig. 13-1d. Since a portion of the control objective is plished by the passive system, less active control effort, implying less power resource, is required.Similar control resource savings can be achieved usin

24、g the semi-active control scheme sketched in Fig. 13-1e, where the control actuators do not add mechanical energy directly to the structure, hence bounded- input/bounded-output stability is guaranteed. Semi-active control devices are often viewed as controllable passive devices.A side benefit of hyb

25、rid and semi-active control systems is that, in the case of a power failure, the passive components of the control still offer some degree of protection, unlike a fully active control system.混合控制和半主动控制的特点和优势portion，部分； imply，意味着；bound，边界。13.2 Basic Principles 13.3 Passive Energy DissipationDiscussio

26、ns presented below are centered around some of the more common devices which have found applications in PED.13.3.1 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. Many o

27、f these devices use mild steel plates with triangular or X shapes so that yielding is spread almost uniformly throughout the material. A typical X-shaped plate damper or ADAS (added damping and stiffness) device is shown in Fig. 13-2. Other configurations of steel yielding devices, used mostly in Ja

28、pan, include bending type of b and slit dampers and shear panel type. Other materials, such as lead and shape-memory alloys, have also been evaluated. Some particularly desirable features of these devices are their stable hysteretic behavior, low-cycle fatigue property, long term reliability, and re

29、lative insensitivity to environmental temperature. 金属屈服阻尼器 mild steel plates，低碳钢板； uniformly，均匀，一体； b ，蜂窝，弯曲型蜂窝； slit，狭缝； alloys，合金。13.3 Passive Energy DissipationAfter gaining confidence in their performance based primarily on experimental evidence, implementation of metallic devices in full-scale

30、structures has taken place. The earliest implementations of metallic dampers in structural systems occurred in New Zealand and Japan. A number of these interesting applications are reported. More recent applications include the use of ADAS dampers in the seismic upgrade of existing buildings in Mexi

31、co and in the USA. The seismic upgrade project discussed in involves the retrofit of a Wells Fargo Bank building in San Francisco, CA. The building is a two-story nonductile concrete frame structure originally constructed in 1967 and subsequently damaged in the 1989 Loma Prieta earthquake. A total o

32、f seven ADAS devices were employed, each with a yield force of 150 kips. Both linear and nonlinear analyses were used in the retrofit design process. ADAS在San Francisco的应用。kips ，千磅。13.3 Passive Energy DissipationA variation of the devices described above but operating on the same metallic yielding p

33、rinciple is the pression yielding brace, also called the unbonded brace, which has found applications in Japan and the USA. As shown in Fig.13-4, an unbonded brace is a bracing member consisting of a core steel plate encased in a concrete-filled steel tube. A special coating is provided between the

34、core plate and concrete in order to reduce friction. The core steel plate provides stable energy dissipation by yielding under reversed axial loading, while the surrounding concrete-filled steel tube resists compression buckling.介绍了金属屈服构件的一种变体。unbonded ，无粘结的； encased，被包住13.3 Passive Energy Dissipati

35、on13.3.2 Friction DampersFriction dampers utilize the mechanism of solid friction that develops between two solid bodies sliding relative to one another to provide the desired energy dissipation. Several types of friction dampers have been developed for the purpose of improving seismic response of s

36、tructures. An example of such a device is depicted in Fig.13-5. During cyclic loading, the mechanism enforces slippage in both tensile and compressive directions. Generally, friction devices generate rectangular hysteretic loops similar to the characteristics of Coulomb friction. After a hysteretic

37、restoring force model has been validated for a particular device, it can be readily incorporated into an overall structural analysis.摩擦阻尼器的原理。enforces，施加；validated，有效；coulomb friction ，库伦摩擦13.3 Passive Energy Dissipation13.3.3 Viscoelastic Dampers Viscoelastic (VE) materials used in structural appli

38、cations are usually copolymers or glassy substances that dissipate energy through shear deformation. A typical VE damper, which consists of VE layers bonded with steel plates, is shown in Fig.13-6. When mounted in a structure, shear deformation and hence energy dissipation takes place when structura

39、l vibration induces relative motion between the outer steel flanges and the center plates. Significant advances in research and development of VE dampers, particularly for seismic applications, have been made in recent years through analyses and experimental tests.粘弹性阻尼器的原理。viscoelastic ，粘弹性； copoly

40、mers ，共聚物；mounted，安装。13.3 Passive Energy Dissipation13.3.3 Viscoelastic Dampers A seismic retrofit project using VE dampers began in 1993 for the 13-story Santa Clara County building in San Jose, CA. Situated in a high seismic risk region, the building was built in 1976. It is ca 64 m in height and

41、nearly square in plan, with 51 m 51 m on typical upper floors. The exterior cladding consists of full-height glazing on two sides and metal siding on the other two sides. The exterior cladding, however, provides little resistance to structural drift. The equivalent viscous damping in the fundamental

42、 mode was 1% of critical.对结构的抗震升级（加固） cladding，包层，电镀； critical，临界值； glazing，玻璃；13.3 Passive Energy Dissipation13.3.4 Viscous fluid dampers The viscous fluid (VF) devices developed recently include viscous walls and VF dampers. The viscous wall, developed by Sumitomo Construction Company, consists of

43、 a plate moving in a thin steel case filled with highly VF. The VF damper, widely used in the military and aerospace industry for many years, has recently been adapted for structural applications in civil engineering. A VF damper generally consists of a piston within a damper housing filled with a c

44、ompound of silicone or similar type of oil, and the piston may contain a number of small orifices through which the fluid may pass from one side of the piston to the other. Thus, VF dampers dissipate energy through the movement of a piston in a highly VF based on the concept of fluid orificing.粘质液体阻

45、尼器的原理和工作方式。aerospace，航空航天； piston，活塞； silicone，硅酮。13.3 Passive Energy Dissipation13.3.5 Tuned Mass DampersEarly applications of tuned mass dampers (TMDs) have been directed toward mitigation of wind-induced excitations. Recently, numerical and experimental studies have been carried out to examine th

46、e effectiveness of TMDs in reducing seismic response of structures. It is noted that a passive TMDs can only be tuned to a single structural frequency. While the first-mode response of a MDOF structure with TMDs can be substantially reduced, the higher mode response may in fact increase as the numbe

47、r of stories increases. For earthquake-type excitations, the response reduction is large for resonant ground motions and diminishes as the dominant frequency of the ground motion gets further away from the structures natural frequency to which the TMDs is tuned.调谐质量阻尼器的减震特点。be tuned ，调谐；resonant，共振。

48、13.3 Passive Energy Dissipation13.3.6 Tuned Liquid Dampers The basic principle involved in applying a tuned liquid dampers (TLDs) to reduce the dynamic response of structures is quite similar to that discussed above for the TMDs. In effect, a secondary mass in the form of a body of liquid is introdu

49、ced into the structural system and tuned to act as a dynamic vibration absorber. However, in the case of TLDs, the damper response is highly nonlinear due either to liquid sloshing or the presence of orifices. TLDs have also been used for suppressing wind-induced vibrations of tall structures. In co

50、mparison with TMDs, the advantages associated with TLDs include low initial cost, virtually free of maintenance and ease of frequency tuning.The TLD applications have taken place primarily in Japan for controlling wind-induced vibration. Examples of TLD-controlled structures include airport towers a

51、nd tall buildings.调谐液体阻尼器的机理和应用特点及优势sloshing ，冲击，晃荡； suppressing，抑制； virtually ，几乎。13.4 Active, Hybrid and Semi-active Control Systems The rapid growth of research interest and development of active/hybrid and semi-active structural control systems is in part due to several coordinated research effo

52、rts, largely in Japan and the USA, marked by a series of milestones listed in Table 13-2. Indeed, the most challenging aspect of active control research in civil engineering is the fact that it is an integration of a number of diverse disciplines, some of which are not within the domain of tradition

53、al civil engineering. These include computer science, data processing, control theory, material science, sensing technology, as well as stochastic processes, structural dynamics, and wind and earthquake engineering. These coordinated efforts have facilitated collaborative research efforts among rese

54、archers from diverse backgrounds and accelerated the research- to-implementation process as one sees today.主动控制是多学科综合的研究领域coordinated ，协同； disciplines，学科； stochastic ，随机的。13.4 Active, Hybrid and Semi-active Control Systems As alluded to earlier, the development of active, hybrid, and semi-active con

55、trol systems has reached the stage of full-scale applications to actual structures. Other than these installations in building structures and towers, most of which are in Japan, 15 bridge towers have employed active systems during erection in addition. Most of these full-scale systems have been subj

56、ected to actual wind forces and ground motions and their observed performances provide invaluable information in terms of:1) validating analytical and simulation procedures used to predict actual system performance2) verifying complex electronic-digital-servo hydraulic systems under actual loading c

57、onditions.3) verifying capability of these systems to operate or shutdown under prescribed conditions.主动系统观测到的数据的用途 。Erection，建造； prescribed，规定的；as alluded to earlier，如前文所述； electronic-digital-servo hydraulic systems，数电液压系统。13.4 Active, Hybrid and Semi-active Control Systems Described below are seve

58、ral of these systems together, in some cases, with their observed performances. Also addressed are several practical issues in connection with actual structural applications of these systems.13.4.1 Hybrid Mass Damper SystemsThe HMD is the most common control device employed in full-scale civil engin

59、eering applications. HMD is a combination of a passive TMDs and an active control actuator. The ability of this device to reduce structural responses relies mainly on the natural motion of the TMDs. The forces from the control actuator are employed to increase the efficiency of the HMD and to increa

60、se its robustness to changes in the dynamic characteristics of the structure. The energy and forces required to operate a typical HMD are far less than those associated with a fully AMP system of comparable performance.下文重点讲述系统、应用的表现和连接方面的问题。HMD的工作特点和优点。 comparable，可比的。13.4 Active, Hybrid and Semi-a