Research Journal of Applied Sciences, Engineering and Technology 4(11): 1590-1594, 2012
ISSN: 2040-7467
© Maxwell Scintific Organization, 2012
Submitted: January 14, 2012
Accepted: March 10, 2012
Published: June 01, 2012
Assement of the Seismic Behavior of Eccentrically Braced frame with Vertical and
Horizontal Link Made of Easy-Going Steel and Constructional Steel
1
Yaser Mozaffary Jouybary and 2Abbas Akbarpour Nikghalb
1
Jouybar Branch, Islamic Azad University, Jouybar, Iran
2
Deptartement of Civil Engineering, Islamic Azad University Tehran South Branch, Iran
Abstract: Eccentrically braced frames (EBFs) are a lateral load resisting system for steel building that are
capable of combining high stiffness in the elastic rang with good ductility and energy dissipation capacity in
the inelastic rang. There are two type eccentrically braced frame; eccentrically braced frame with vertical link
and horizontal link .Eccentrically braced frame with vertical link prevent rotation mean beam and cause
decreased damage in the main structure. During extreme loading it is anticipate that the link beam will deform
inelastic ally with significant ductility and energy dissipation. In the study, lower strength steel is used for the
link beam according to the general concept of Easy-Going steel (EGS).the link beam made of EGS yields in
improved. The obtain this objectives, 3-D steel building in 4,8 and 12 story by short link beams made of EasyGoing steel and constructional steel were modeled. 10 near-field ground motions were utilized as input ground
motions. Based on nonlinear analysis, the values of story displacement, inter story drift, story acceleration and
velocity, base shear, for shear link beams system under near - field earthquake were investigated and the results
have been discussed. It is found that the use of EGS in link beam decrease lateral displacement .By decrease
the lateral displacement, damage in the structure decreased. Also the link beam made of EGS yields less
displacement and so the energy dissipation capacity increased. It is found that the use vertical link in the
eccentrically braced frame prevent rotation mean beam; also system EBFs with vertical link yielded lees
displacement and so the energy dissipation capacity increased.
Key words: Eccentrically Braced Frame, Vertical Link, Horizontal Link, Easy-Going Steel
INTRODUCTION
METHODOLOGY
Because of proper seismic characteristic of
eccentrically braced frames, the use of lateral resisting
structural system is quite popular in the region with
high level of seismicity. In the type of frames a distance
is created between the two ends of the bracing
members, bracing member and column or bracing
member and beam, is called link beam(e), as shown in
Fig. 1. The link beam acts as a fuse and prevents the
other members of frame to enter the inelastic range. The
link absorbs a significant amount of energy by inelastic
deformation.
One of the advantage of vertical links over their
horizontal link counterparts is the exclusion of plastic
deformation from the main structure result on no
damage in the structural under sever earthquakes; easy
and sample rehabilitation; and the replacement of link
after earthquake. In this study, Easy-Going steel is used
to make the link beam and the behavior of link studied
and compared to those of a link made of constructional
steel, because the link beam of EGS yields in less
displacement and so the energy dissipation capacity is
significantly improved (Sabouri and Ziaei, 2008;
Mohsenali-Rezaeian and Taherkhani, 2008).
Mechanism of horizontal link beam: The length of
link beams effect the behavior of EBFs in linear and
non-linear region. In high force the plastic hinges were
created in link beam that the kind of these indicates the
mechanism of link beams. By writhing the stability
equation we have these two boundaries. In this Eq. (1)
is the length of link beam:
Shear link beam e ≤
16
. MP
VP
Moment link beam e >
(1)
2.6 M P
VP
when the length of link beam is between theses
limitations both shear and moment mechanisms occur.
UBC code limits the ultimate rotation of link beams,
0.09 for shear ones and 0.03 for moment ones. AISC
limitations are 0.08 for shear link and 0.03 for moment
links. These limitations in Iran code are 0.08 for shear
link and 0.02 for moment links (Tehrani and Haj,2008).
Corresponding Author: Yaser Mozaffary Jouybary, Jouybar Branch, Islamic Azad University, Jouybar, Iran
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Res. J. Appl. Sci. Eng. Technol., 4(11): 1590-1594, 2012
Fig. 1: Link in eccentrically braced frame
Table 1: Specification of EGS steel and constructional steel
Elasticity Yield stress Ultimate stress
modulus
(Mpa)
(Mpa)
Constructional steel
2.1E10
240
400
Easy-going steel
2.1E10
110
250
Fig. 2: The diagram of the moment in frame with single
vertical link
Fig. 3: Plan building
Mechanism of vertical link beam: For vertical shear
links whose moment diagram is illustrated in Fig. 2, in
order to achieve the shear hinges formation condition
before flexural hinge, due to the unequal moment at the
end of link Eq. (2) considered:
e≤
0.8( K + 1) M P
M2
, ( M 2 ≤ M1 )
K=
VP
M1
(2)
Modeling: In the research the EBF systems with
vertical and horizontal link with shear behavior made of
EGS and ST37 have modeled. (Table 1)Short link beam
considered equal to 0.5 m, in 4, 8 and 12 numbers of
stories, respectively. The height of each story in 3
m.The plan of structure in all stories is similar. This
plan has 4 longitudinal spans and 4 spans in other side.
Each span has 4 m length, as shown in Fig. 3.
Consideration of soil is according to soil type II
(Iran 2800 code) similar to zone 4 (UBC 97). All
models have residential use. The earthquake
probabilistic hazard considered very high. For each
model loading complete design is separately done
according to Iran Earthquake code (2800) (much similar
to UBC97) and steel design code (much similar to
AISC89). IPE and plate girders are use for beams, BOX
sections are used for columns for doing all step of
analysis and design we use program sap 2000 v.14.1.1.
In research, non-linear static analyses and non-linear
dynamic analyses performed.
Near-field earthquake: Near-Field earthquake have
some characteristic that differ them from Far-Field
ones. These earthquakes have higher acceleration and
restricted frequency content in higher frequencies that
Far-Field ones.(Table 2)Also their records have pulses
in beginning of record with high period and high
domain. These pulses are much considerable when the
forward directivity takes place, therefore the records
change from board-band condition to pulse-like ones.
All of them have distance less than 10 km (Tehrani and
Haj, 2008).
Non-linear static analysis: Plastic hinges definition,
assignments and non-linear static analysis are done
according to Feta 356. The plastic hinges were
produced only in link beam, production of hinges has
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Res. J. Appl. Sci. Eng. Technol., 4(11): 1590-1594, 2012
Table 2: Specification of near-field motions
Number
Earthquake
Year
1
Bam
2003
2
Tabas
1978
3
Chi chi
1999
4
Kobe
1995
5
Northridge
1994
6
Landers
1992
7
Golbaf
1998
8
Silakhor
2006
9
Zangiran
1994
10
Kocaeli
1999
PGA (g)
0.78
0.328
0.328
0.59
0.433
0.274
0.29
0.44
0.91
0.376
400
Base reaction (ton)
Base reaction (ton)
PGD (cm)
34.480
12.56
41.87
19.95
7.21
9.82
5.87
28.9
27.3
70.52
Station
Bam
Dayhook
TCU
o kjma
acoima
Joshua
Golbaf
Silakhor
Zangiran
Sakavya
600
500
300
200
100
400
200
0
0
0
10
20
30
Displacement (cm)
0
40
5
10
15
Displacement (cm)
20
25
500
700
Base reaction (ton)
600
Base reaction (ton)
PGV (cm/sec)
123.69
20.6
68.8
74.3
51.5
27.5
14.126
84.9
69
79.5
500
400
300
200
500
300
200
100
100
0
0
0
10
20
30
40
Displacement (cm)
50
0
60
10
5
15
20
Displacement (cm)
25
30
regular processes, it mean that before producing plastic
hinges in all of stories, the structural do not go under
instability and collapse mode. Non-linear static analysis
do, are investigate the First plastic hinges in the
building with link beam mode of EGS were produced
in the less displacement, as the energy dissipation
capacity increased. Also are investigate the First plastic
hinges in the building with vertical link beam were
produced in the less displacement, as the energy
dissipation capacity increased.
The base shear gets form vertical link, is so lees
that base shear get form horizontal link shown in the
Fig. 5. Also the base shear gets form link beamed made
of EGS, is so lees that base shear get form link beam
made of st 37 shown in the Fig. 6. For each model,
among non-linear static analysis that have we choose
critical analysis,as pushover curves shown in the Fig. 4.
Base reaction (ton)
Fig. 4: Base shear-displacement diagrams (pushover curves)
550
500
450
400
350
300
250
200
150
100
50
0
4-stories
8-stories
12-stories
H-EBF
(St37)
H-EBF
(EGS)
V-EBF
(St37)
V-EBF
(EGS)
Fig. 5: Comparison base shear buildings
Non-linear dynamic analysis: All the non-linear
dynamic analyses are as Direct Integration time history.
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10
Displacement (cm)
38.4
35.2
32.0
28.8
25.6
22.4
19.2
16.0
12.8
9.6
6.4
3.2
0
15
H-EBF (St37)
H-EBF (EGS)
V-EBF (St37)
V-EBF (EGS)
0
1
2
3
4
5
6
7
8
9
10
7
8
9
10
7
8
9
10
-5
-10
-15
-20
Time (sec)
15
0
15
10
Lateral displacement (cm)
5
H-EBF (St37)
H-EBF (EGS)
20
10
25
V-EBF (St37)
V-EBF (EGS)
5
0
-5 0
1
2
3
4
5
6
-10
25.6
Height (m)
5
0
Displacement (cm)
Height (m)
Res. J. Appl. Sci. Eng. Technol., 4(11): 1590-1594, 2012
22.4
-15
19.2
-20
Time (sec)
16.0
Fig. 7: Roof displacement curves
12.8
9.6
15
6.4
10
0
0
2
4
6
Lateral displacement (cm)
Moment (ton.m)
3.2
8
5
0
-5
0
1
2
3
4
5
6
-10
Fig. 6: Formation first plastic hinges in the building
-15
-20
Time (sec)
15
10
Moment (ton.m)
Tabas, Landers and Northridge Earthquske are selected
for non-linera dynamic analysis;Also effective vertical
component Tabas earthquake considred. For each
modle, non-linear dynamic analyses done. In a
building, all non-linear deformation occurred in link
beams which indicate that all the energy dissipation
capacity is due to the existence of links and all other
parts of the structure remain in the linear range the use
of EGS in link beam EBF decreases lateral
displacement in different stories in building. In the 8
stories, lateral displacement decrease 50% in
comparison link beam made of st 37, as shown Fig. 7.
By decreasing the lateral displacement, the moment in
the vertical load-carrying member like columns are
decreased, as shown Fig. 8, so decreased damaging in
the structure and the section structural column
decreased. The use of EGS in link beam yields in the
less displacement and so the energy dissipation capacity
increased.
Under Near-Field earthquake and under non-linear
dynamic analyses the amount of relative acceleration
and velocity in link beam mode of EGS are less than
link beam made of st 37. Also, Under Near-Field
earthquake and under non-linear dynamic analyses the
5
0
0
1
2
3
4
5
6
7
8
9
10
-5
-10
-15
Time (sec)
Fig. 8: Moment curves for column one story
amount of relative acceleration and velocity in vertical
link beam are less than horizontal link, as shown Fig. 9.
RESULTS
C
1593
The non-linear lateral displacement in EBFs with
link beam made of EGS become less than EBF
with link beam of st 37.
Res. J. Appl. Sci. Eng. Technol., 4(11): 1590-1594, 2012
Tabas-horizontal
Tabas-vertical
Northridge
Landers
8
7
5
4
3
2
1
0
0
300
900
1200
600
Relative acceleration (cm/sec)
1500
Tabas-horizontal
Tabas-vertical
Northridge
Landers
8
7
6
0
600
800
400
Relative acceleration (cm/s2)
1000
Tabas-horizontal
Tabas-vertical
Northridge
Landers
12
11
10
9
8
7
6
5
4
3
2
1
0
5
200
Story
Story
12
11
10
9
8
7
6
5
4
3
2
1
0
Story
Story
6
Tabas-horizontal
Tabas-vertical
Northridge
Landers
4
3
2
1
0
0
10
30
40
20
Relative velocity (cm/s2)
0
50
10
50
30
20
40
Relative velocity (cm/s2)
60
70
Fig. 9: Comparison relative acceleration and velocity different earthquake
C
C
C
C
The non-linear lateral displacement in EBFs with
vertical link beam become more than EBF with
horizontal link beam
The use of EGS in the link beam decrease lateral
displacement. By decrease the lateral
displacement, damage in the structure decreased.
Also the link beam made of EGS yields less
The base shear get from vertical link beam, is so
less that base shear get from horizontal link beam.
displacement and so the energy dissipation
capacity increased. Also the use of EGS in the link
beam decreased base shear in comparison link
beam made of st 37.
Under Near-Field earthquake and under non-linear
dynamic analyses the amount of relative
acceleration and velocity in link beam mode of
EGS are less than link beam made of st 37. Also,
Under Near-Field earthquake and under non-linear
dynamic analyses the amount of relative
acceleration and velocity in vertical link beam are
less than horizontal link.
C
In EBF systems with short links have good
performance in the earthquakes.
REFERENCES
Mohsenali-Rezaeian, S. and S. Taherkhani, 2008.
Assessment of the seismic behavior of
eccentrically braced frame with double vertical
link (DV-EBF). The 14 world Conference on
Earthquake Engineering October 12-17, Beijing,
China.
Sabouri, S. and M. Ziaei, 2008. A Study on the
Behavior of shear Link Beam of Easy-Going steel
in Eccentrically Braced Frames. The 14 world
Conference on Earthquake Engineering October
12-17, Beiging, China.
Tehrani, Z.M. and N.L. Haj, 2008. Assessing Seismic
Behavior of Eccentrically Braced Frames (EBFs)
Due to Near-Field Ground Motions. 14 World
Conferences on Earthquake Engineering October
12-17, Beijing, China.
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