Usage of energy dissipation technology in tall building strcuture

Reading Report of
Tall Building Structure
Major：
Structural Engineering
ID NO：
1130411
Name：
王瑞
1
Usage of Energy Dissipation Technology
in Tall Building Structure
【 Abstract 】 With the developing of tall building structure theory and the
application of new material and new technology, the height of high-rise building is
increasing and the body type is becoming more complicated, which make it hard to
satisfy the seismic requirements with regular structure system only. As a method that
can solve the seismic problems properly, the energy dissipation technology has been
widely used in design of high-rise building. A brief introduction of energy dissipation
technology and the usage of it in tall building structures are given in this report.
【Keyword】seismic design, energy dissipation technology, tall building structure
1 Introduction of energy dissipation technology
The theoretical basis of energy dissipation system will be introduced through an
example of single-degree of freedom system. The system is composed by a
concentrated mass m in the top, a frame without mass to provide the stiffness and a
viscous damper to dissipate the seismic energy. Assuming there is no axial
deformation in the beams and the columns. The system is presented in Fig.1.
Fig.1 Single-degree of freedom system
The differential equations of motion of this system under harmonic force is
mu ''  cu '  ku  P0 sin wt
The steady-state displacement response can be calculated as
u (t )  u0 sin( wt   )  (ust )0 Rd sin( wt   )
The displacement reaction coefficient can be described as
2
Rd 
u0

(ust )0
1
2
1  ( / n ) 2    2 ( / n )2 
2
From the equations above, the displacement reaction coefficient is becoming
smaller with the increase of damping ratio or damp, which means smaller
dynamic response amplitude. This is the theoretical basis of energy dissipation
technology. We can take measures to increase the damp of the system to dissipate the
seismic energy and thus reduce the dynamic response of structure [1].
The energy dissipation technology mainly includes energy dissipation devices
like dampers and damping constructions like energy dissipation brace. These devices
and constructions can provide additional stiffness and additional damp for the
structure to dissipate the seismic energy and reduce the dynamic response under
earthquake, which reduce the earthquake disaster effectively. These devices can
provide high stiffness under the action of wind or small earthquakes. At the same time
they can turn into inelastic or yield firstly under severe earthquakes to increase the
damp and dissipate the energy [2].
2 Energy dissipation devices
The basic idea of energy dissipation devices is that these devices won’t
undertake the load directly under normal circumstances but can share part of the load
and dissipate the dynamic energy under certain vertical load, which can reduce the
response of the structure [1].
The most common energy dissipation device in use is the damper (Fig.2).
Dampers are usually installed in locations like braces, joints between beams and
columns, joints between frames and shear walls, bottom chords of trusses and so on [3].
When earthquake happens, the damping force will do work under the relative motion
caused by earthquake and dissipate the dynamic energy. This process can translate the
kinetic energy into heat and reduce the earthquake response. The most prominent
advantage of dampers is that it won’t change the original structure system [4]. This
kind of energy dissipation devices has been widely used in seismic design in China.
Fig.2 dampers in structure
3
3 Energy dissipation constructions
Energy dissipation construction is a broad concept. The main measure is to
improve the energy dissipation capability by certain construction design. To achieve
this purpose, we usually prefer bending energy consumption to shear energy
consumption or axial energy consumption because of its full hysteresis curve. We can
also design to achieve the purpose that some components can enter plastic state to
dissipate the dynamic energy thus protect the main structure. Energy dissipation
braces, energy dissipation shear wall, energy dissipation joints and connections are
main kinds of energy dissipation construction in use.
3.1 Energy dissipation braces
(1) Cross energy dissipation brace
This kind of brace is based on the theory of HADAS (one kind of hysteretic
dampers). It can dissipate dynamic energy through the plastic deformation of steel
frames located in the cross position of the brace.
(2) Friction energy dissipation brace
Friction dampers composed by high-strength bolts and steel plates are installed
in this kind of brace. It can provide high stiffness without apparent slide under the
action of wind or small earthquake. On the other hand it will slide under severe
earthquake and reduce the stiffness of structure. The friction in brace can dissipate the
energy and reduce seismic response of structure [5].
Fig.3 The computational model for friction energy dissipation brace
(3) Eccentric energy dissipation brace
This kind of brace is often used in steel frame structure. It can dissipate seismic
energy through the plastic deformation of eccentric beam section. The eccentric beam
4
will not yield under the action of wind or small earthquake and can provide enough
stiffness [6]. The brace will yield under big earthquake and dissipate energy.
Fig.4 Regular eccentric brace system
3.2 Energy dissipation wall
Energy dissipation wall is based on the theory of dampers or install them directly
on shear walls or non-bearing walls. It mainly concentrated on the construction
measures to deal with the connection parts between walls and frames or the gaps
between walls and frames which can control the value of shear force acted on the wall
and the deformation capability. These construction measures can help dissipating the
dynamic energy [7].
Besides, buckling restrained brace is also one kind of energy dissipation
constructions widely used. For traditional braces, the compression strength is much
smaller than tensile strength and the buckling of braces can badly influence the
stiffness, bearing capacity and the earthquake resistant behavior. Buckling restrained
brace is composed of both steel and concrete to make sure that the braces will not
buckle under compression force. So the compression strength is equal to the tensile
strength. The ductility and hysteresis ability are also improved. This kind of braces
can dissipate the dynamic energy through the yielding of steel in serious earthquake.
4 Energy dissipation structure systems
Many kinds of new structure systems are designed to improve the energy
dissipation capability in recent years. Some typical examples will be introduced in
this part.
4.1 RC tube in tube structure with friction joints
The friction joints in RC tube in tube structure is composed of frame tube, wall
tube and the friction joint devices (Fig.5). Certain gaps are set up in the slabs
connecting the frame tube and wall tube where friction joint devices are installed.
Under severe earthquakes，the differential movement between the frame tube and the
5
wall tube causes hysteretic energy dissipation by the friction joints slipping [8].
Fig.5 Friction joints in RC tube in tube structure
This kind of structure system can improve the seismic performance in two
aspects. Firstly, the deformation modes of frame tube and wall tube are different
under lateral loads. The deformation of frame tube is bending type and that of the wall
tube is shearing type. The friction joints will do work caused by the different
deformation of these two parts. Secondly, under severe earthquake, especially when
the seismic predominant period is closed to the natural period of structure, resonance
can be easy to happen in the structure. The friction joints can help to change the
overall stiffness of structure and the natural period, which can avoid the resonance [9].
4.2 Energy dissipation structure system with high-level transfer floor
With the rapid development of high rise buildings in recent years，in order to
meet the functional requirements，the lower part of many high rise buildings is always
frame structure so that it can provide large space for commercial purpose，and the
upper part is often used as residence or hotels which need relatively small space.
Complex structural forms of high rise structure with high-level transfer floor are
proposed and widely used in China. But a significant problem is that the vertical
stiffness is not continuous that may causes damage concentrated in the parts near the
transfer floor. The internal force and deformation of components on different sides of
the transfer floor can also change suddenly which is dangerous in severe earthquakes.
To solve these problems, experts propose to apply energy dissipation devices in
the structures with high-level transfer floor. In this new structure system, damping
devices like dampers or braces are installed in the lower part to the high-level transfer
floor and replace some of the shear walls (Fig.6). These devices can act as subsidiary
components under normal circumstances. Under severe earthquake, they will provide
additional stiffness and damp to the structure and change the dynamic response to
reduce damage to the main structure [10].
Energy dissipation devices can also be installed in the transfer floor thus won’t
influence the functional requirements of architecture.
6
Fig.6 Energy dissipation structure system with high-level transfer floor
5 conclusion and advices
The research of energy dissipation technology has developed rapidly in recent
years in China. The technology has been applied in many tall building structures and
improved the seismic performance of structures significantly. But there are still many
problems to be solved.
(1) More research about the durability and reliability of energy dissipation
devices should be taken to improve the function of them.
(2) More experiments are needed to test the seismic performance of structures
with dampers or damping braces to get the detailed character.
(3) Research about the design method and specialized code are needed to
standardize the usage of energy dissipation technology.
(4) Application of the energy dissipation technology in complicated structures is
quite important and more work can be done to design new kinds of energy dissipation
structure systems
As a conclusion, energy dissipation technology is acting an important role in
seismic design of tall building structures with a bright future in application.
7
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