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
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Dlapl8cernent (Inch) ·1 0 1
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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).