Manual 21225615

Manual 21225615
9th International Conference on Urban Earthquake Engineering/ 4th Asia Conference on Earthquake Engineering
March 6-8, 2012, Tokyo Institute of Technology, Tokyo, Japan
Siavash Soroushian1), ManosMaragakis2), Keri L. Ryan3), Eiji Sato4), Tomohiro Sasaki5), Taichiro
Okazaki6), Lee Tedesco7), Arash E. Zaghi8), Gilberto Mosqueda9), and Dennis Alvarez10)
1) PhD Candidate, Civil and Environmental Engineering, University of Nevada, Reno, USA
2) Dean, and Professor, Civil and Environmental Engineering, University of Nevada, Reno, USA
3) Assistant Professor, Civil and Environmental Engineering, University of Nevada, Reno, USA
4) Senior Researcher , Hyogo Earthquake Engineering Research Center (E-Defense), National Research Institute for Earth Science and
Disaster Prevention, Japan
5) Researcher , Hyogo Earthquake Engineering Research Center (E-Defense), National Research Institute for Earth Science and Disaster
Prevention, Japan
6) Associate Professor, Faculty and Graduate School of Engineering, Hokkaido University, Japan
7) Manager, Building Science, USG Building Systems, USA
8) Assistant Professor, Department of Civil and Environmental Engineering, University of Connecticut, Storrs, USA
9) Associate Professor, Civil, Structural and Environmental Engineering, State University of New York at Buffalo, USA
10) Consulting Engineer, 987 Valley Creek Drive, USA
[email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected];
[email protected]; [email protected]; [email protected]; [email protected]
Abstract: Nonstructural systems constitute a significant portion of the total property of typical buildings. Recent
earthquakes have conclusively demonstrated that nonstructural damage results in significant loss of property and function
with major catastrophic impact on communities. As part of the NEESR-GC project on the ”Simulation of the Seismic
Performance of Nonstructural Systems” and in a collaborative effort with NEES TIPS and NIED, a full-scale, five-story
steel moment frame building in base-isolated and fixed-base configurations was subjected to a number of 2D and 3D
ground motions using the E-Defense shake table. The building was tested under three different configurations: 1) base
isolated with triple pendulum bearings (TPB), 2) base isolated with a combination of lead-rubber bearings and cross
linear bearings (LRB/CLB), and 3) fixed base. For this experiment, more than 800 sq-ft of suspended ceiling with lay-in
tiles and 3 sprinkler branch lines were installed on the 4th and 5th floors of the building. This paper presents some of the
preliminary observations related to the response of nonstructural systems from these experiments.
The total repair and replacement cost of nonresidential
buildings after the Northridge earthquake was $6.3 billion,
only $1.1 billion of which was due to structural damage
(Kircher 2003). Immediately after this earthquake, 88% of
the occupants of hospital beds in the damaged area (13
hospitals) were evacuated as a result of water damage,
elevator failure, and other nonstructural damage (Ayres et al.
1998). Minimal structural damage was observed in hospitals
that met the requirements specified in the 1973 Hospital Act.
Nevertheless, even in hospitals constructed after 1973, and
which survived strong ground motions, nonstructural
damage of the plumbing, ceiling systems, etc., was extensive.
This demonstrates an urgent need to better understand the
seismic behavior of nonstructural systems.
The nonstructural design provisions cannot be
improved without strategically collected experimental data
that supplement field observation. Several studies have been
conducted on the seismic response of nonstructural
subassemblies and their components, such as ceiling tiles
and piping systems, as early as the 1980s (ATC 2007). Our
understanding of the system-level response of nonstructural
systems remains very limited, and could be improved
substantially by large-scale experiments on complete
systems (Zaghi et al. 2010).
As part of a collaboration between the “NEESR-GC:
Simulation of the Seismic Performance of Nonstructural
System” and the National Research Institute for Earth
Science and Disaster Prevention (NIED) of Japan, a series of
partitions-ceilings-sprinkler piping systems were conducted
at the Hyogo Earthquake Engineering Research Center, also
known as E-Defense, of NIED. This paper reports on the
response of the ceiling and fire sprinkler piping systems,
which were installed in a full-scale building tested in three
different configurations: 1) base isolated with triple
pendulum bearings (TPB), 2) base isolated with a
combination of lead-rubber bearings and cross linear
bearings (LRB/CLB), and 3) base fixed.
Hanger Wire
Seismic Brace
Light Representative
Main Runner
122 cm (4 ft) Long Cross Tee
Nonstructural elements were installed in a 5-story steel
moment frame building (Figure 1) that was tested for the
NEES TIPS/E-Defense project. This building is
approximately 16 m (53 ft) tall, and asymmetric in plan with
dimension of 10 m (33 ft) by 12 m (40 ft) (2 bays by 2 bays)
(Figure 2). Further information about the building is
provided in Kasai et al. (2010).
The building weighed about 5,300 kN. The dynamic
properties of the building measured and reported from
previous tests are: natural period = 0.68 sec, damping ratio =
2%. The modeling and analysis of the building specimen for
2011 experiments will be reported in future papers;
61 cm (2ft) Long Cross Tee
Figure 1 5-Story Steel Moment
Figure 2 Top: Plan
Frame Specimen Set on Triple
View, Bot.: Elevation
Pendulum Isolators
preliminary results suggest the specimen in the fixed-base
configuration may have responded with slightly longer
period and greater damping ratio than in previous tests.
Two isolation systems were considered and designed in
addition to the fixed base configuration in this experiment.
The first isolation system incorporated 9 identical TPBs, one
beneath each column, which were manufactured by
Earthquake Protection Systems. The second isolation system
incorporated 4 LRBs manufactured by Dynamic Isolation
Systems and 5 CLBs manufactured by THK according to
design specified by Aseismic Devices Company (ADC).
Additional details of the isolation design are provided in
(Ryan et al. 2012).
A partition-ceiling-sprinkler piping subassembly was
designed and installed in nearly identical configuration over
two complete floors of the building specimen. These
components were installed on the 4th and 5th floors, which
were expected to draw the maximum floor accelerations.
3.1 Suspended Ceiling
The layout of the ceiling system for each floor is shown
in Figure 3, along with a photograph of the grid system prior
to the panel installation. The ceilings were installed in the
test frame per ASTM E580/E580M-11ae1 (ASTM 2011).
The grid was constructed using the heavy-duty USG DONN
23.8 mm (15/16 in) exposed tee system. Main runners and
cross tees were aligned as shown in Figure 3(a). The main
runners were hung with 12-gauge Hilti X-CW suspension
wires spaced 1.2 m (4 ft) apart; additional wires supporting
all perimeter grid pieces were placed within 200 mm (8 in)
from the face of the partition wall. The ceiling was
suspended 1 m (3 ft) from the bottom of the structural deck.
A 22 mm (7/8 in) wall molding was attached to the
perimeter partition walls. At the North and East ends, the
Hanger Wire
61 cm Cross Tee
122 cm Cross Tee
Main Runner
Figure 3: Overall View of Ceiling System; (a)
Layout; and (b) Photograph of Grid Prior to
Panel Installation
main runners and cross tees were attached tight to the wall
molding using USG/ACM7 seismic clips with one partition
attached screw and one top hole screw to prevent movement
of ceiling grids (Figure 4(a)). At the South and West ends,
the main runners and cross tees were attached with 19 mm
(3/4 in) clearance to the wall molding using the same
seismic clip, but with the second screw attached at the
middle of the clip slot to allow the grid members to float
freely (Figure 4(b)). At the hatched grids in Figure 3(a),
heavier gypsum board panels were used to represent the
weight of light fixtures.
ASTM E580/E580M-11ae1 (ASTM 2011) require
seismic braces to be placed in ceiling areas larger than 93
m2 (1,000 ft2). To compare the behavior of braced and
unbraced ceiling systems, the seismic braces were only
installed on the 5th floor ceiling while all other details were
Top Hole Screw
ACM7 Seismic Clip
main run intersections were grooved fit, while the rest of the
connections were threaded. Branch Lines 1 and 2, each with
three 305 mm (12 in) drops, incorporated armover drops and
straight drops, respectively. At the first drop of each branch
line, a 50 mm (2 in ) oversized ring was used at the location
of the sprinkler heads (oversized gap configuration, Figure
7(a)), while only minimal gap was provided for the rest of
drops (no gap configuration, Figure 7(b)). A Victaulic
Aquaflex Flexible drop was used at Drop 2 of Branch Line 3
(Figure 7(c)).
Middle Slot Screw
On each floor, the piping system was supported by
vertical pipe hangers at 9 locations, 4 for the main run and 5
for the branch lines (Figure 8(a)). The pipe hangers consisted
of 9.5 mm (3/8 in) diameter and 457 mm (1.5 ft) long
threaded rod.
Branch Line 2
Branch Line 1
Partition Attach Screw
19mm (3/4 in) clearance
Pipe Hanger &
Wire Restraints
Figure 4 Joint Between Runners/Cross Tees and Wall
Molding: (a) Attached Detail, and (b) Unattached
to Float)
identical on both floors.
brace consisted of: 1)
25mm (1in.)
Branch Line 3
Pipe Sway
Solid Brace
Pipe Hanger
80mm (3 in.) Riser
Figure 6
Arm Over Drop
32mm (1.25 in.)
a system of splay wires or a rigid brace and 2) a
USG/VSA30/40 compression post. The seismic braces were
placed at 3.6 m (12 ft) on center, in each direction, with the
first set occurring within 1.8 m (6 ft) of the face of the wall.
Four wires splayed at 90° from each other were attached to
the main runner within 50 mm (2 in) of an intersection with
cross members (Figure 5). In some locations, due to the
geometry and connection constraints, steel stud compression
posts were used instead of USG/VSA30/40 compression
posts and/or 2 way steel stud rigid braces were used in place
of two of the splay wires.
65mm (2.5 in.) Main Run
Overall Plan View of Piping System
Compression Post
Diagonal Splay Wires
Figure 5
Seismic Bracing for the Ceiling
Ceiling Grid
3.2 Fire Sprinkler Piping
A standard Schedule 40 piping system was attached to
the specimen per NFPA 13 (NFPA 2011). The piping system
included one 80 mm (3 in) diameter riser pipe, one 65 mm
(2.5 in) diameter main run and three (North-South) 32-25
mm (1.25-1 in) diameter branch lines (Figure 6). All
connections on the riser, the main run, and branch line to the
Figure 7 Sprinkler Heads and Drops: (a) 50 mm (2 in.)
Oversized Gap Configuration, (b) No Gap Configuration,
and (c) Flexible Drop
Lateral resistance was provided by inclined 25 mm (1
in) diameter longitudinal and lateral pipe sway braces on the
main run near the riser pipe (Figure 8(b)), a lateral pipe sway
brace at the end of the main run, and two longitudinal braces
at the end of the riser pipe below the 4th floor deck. The
ends of the branch lines were restrained with two diagonal
splay wires to limit the lateral movement (Figure 8(a)).
Pipe Hanger
Lateral Brace
Diagonal Wires
Longitudinal Brace
Figure 8 Bracing for Piping System: (a) Diagonal
Splay Wires and Pipe Hanger at the End of Each Branch
Line, and (b) Lateral and Longitudinal Brace Near Riser
The building was subjected to a variety of horizontal
(2D) and combined horizontal and vertical (3D) ground
motions. The applied ground motions are summarized in
table 1. Due to the flexibility of the decks, the vertical
acceleration was generally amplified in the middle of the
decks compared to the column locations. Also, the
North-East and South-East side of the roof deck experienced
the largest vertical acceleration due to supplementary
roof-mounted mass (Ryan et al. 2012). Table 2 lists the
vertical natural frequency of the 5th and 6th decks that were
evaluated from tri-axial white noise excitation of the
fixed-base specimen.
Table 2 Vertical Vibration Frequency of 5th
and 6th ( Roof ) Deck
More than 350 instrument channels were used to
monitor the response of the shake table, structural frame,
floor slabs, and individual nonstructural components.
Three-axis accelerometers were placed on the shake table,
on each floor near the corner columns (Figure 9), on the
ceiling grid of the 4th floor ceiling and the compression
posts of the 5th floor ceiling (Figure 10), on one ceiling
panel at each floor (C9 of Figure 10), and on various
locations on the pipes. Uniaxial (vertical) accelerometers
were placed on each floor deck to evaluate the vertical
motion (Figure 9). Displacement transducers were used to
monitor motion of the piping system and displacement at the
perimeter of the ceiling system.
Figure 9: Accelerometers Placed on a
Typical Floor
North- East
South- East
North- West
Frequency (HZ)
While almost no damage to the ceiling-piping system
was observed in response to 2D (horizontal only) ground
excitations, significant damage was observed from 3D
motions with large vertical ground excitation. The greatest
damage was generated by a 3D input ground motion
recorded at Rinaldi Receiving Station during the 1994
Northridge Earthquake (3D-Northridge-Rinaldi) that was
repeated in all three system configurations. (Note that the
scale factor for the horizontal component of excitation was
reduced for the fixed-base building.) Although minor
differences were observed, the damage mechanisms and the
extent of damage (e.g. affected area) were very similar for
the three system configurations. Although the ceiling-piping
system was repaired after each test day, it was never restored
to its original configuration. Thus, unless otherwise noted,
all observations reported here are from the first test that
triggered damage – 3D-Northridge-Rinaldi in TPB isolated
5.1 Ceiling Panel and Grid System Failures
Only at 4th Floor Ceiling
Figure 10: Accelerometers Placed on
a Typical Ceiling System
During the experiments, a maximum of three panels
(1%) from the unbraced (4th floor) ceiling were displaced or
fell to the floor in while up to 40% of the panels in the
braced (5th floor) ceiling were displaced and/or fell. Most of
the damage was located under the North-East and
South-East decks. The condition of the braced and unbraced
ceiling after 3D-Northridge-Rinaldi (TPB system) is
compared in Figure 11. Over the course of the test program,
some of the cross tee sections failed but the main runners
always remained intact.
The accelerations in all three directions at the
deck level, which represent the input excitation to the ceiling
Summary of Target Table/Floor Achieved Motions
system, were slightly higher at the 6th deck than the 5th deck.
However, the input acceleration alone does not explain the
difference in damage; observed accelerations in each ceiling
suggest that the compression posts used in the lateral bracing
increased the damage to the ceiling system in this
experiment. Figure 12 shows the vertical acceleration of a
ceiling panel (C9) and ceiling grid (C4) (see Figure 10)
measured for a moderate excitation (3D-Superstition Hills
Westmorland/TPB system) executed prior to the occurrence
of ceiling damage. In the unbraced ceiling, little
amplification of the panel acceleration relative to the grid
was observed (Figure 12(a)), which suggests that these two
components moved together. However, in the braced system,
the acceleration of the ceiling panel is significantly amplified
relative to the compression post attachment location (Figure
12(b)), which suggests that the panel pounded on the grid
posts at regular intervals. By constraint of the compression
posts, the entire system (deck, grid, and panels) will
generally move together with equal accelerations, as
depicted in case 1. However, during downward deck
Structural Deck
Loose Hangers
= Hangers
Case 1
(Agrid=g) ≠ Adeck
Ceiling Panel
(Apanel = Agrid = g) ≠ Adeck
Apanel = Agrid
Apanel = Agrid = Adeck
Hanger Wire
Ceiling Grid
Figure 13: Vertical Dynamics of Unbraced Ceiling
Structural Deck
Case 2
Case 1
(Apanel = g) ≠ (Agrid = Adeck)
Ceiling Panel Ceiling Grid
Agrid = Adeck
AAgrid ==AAdeck
Apanel= Agrid= Adeck
Compression Post
Figure 14: Vertical Dynamics of Braced Ceiling
Figure 11 Condition of (a) Braced Ceiling (5th Floor)
and (b) Unbraced Ceiling (4th Floor) after
3D-Northridge-Rinaldi (TPB System)
The acceleration trends observed in Figure 12 are
explained as follows: consider the diagram of the ceiling
system in Figures 13 and 14, where the vertical acceleration
of the deck, grid, and panel are labeled Adeck, Agrid, and Apanel,
respectively. Figure 13 depicts the unbraced ceiling, which is
supported only by hanger wires. When the hanger wires are
in tension (case 1), the accelerations of the deck, grid and
panel are the same. However, when the hanger wires are
loose (case 2), which as an example can be initiated by
downward deck acceleration of more than 1g while the
panels and grid system are limited to a maximum of 1g
downward acceleration, the deck acceleration will differ
from that of the panels and grid system. As the panel and
grid system have almost the same acceleration, the panels
will remain in place between the grid members and the
probability of dislodging panels is low.
Figure 14 depicts the braced ceiling with compression
acceleration of more than 1g, the grid system will move with
the deck (assuming the compression posts are rigid) at the
compression post locations while the panels are limited to 1g
downward acceleration.As a result, the deck and grid
accelerations will differ from the panel accelerations,
causing a gap to form between the ceiling grid and panels.
Once the gap forms, the ceiling panels are no longer
constrained by the horizontal forces of the grid system, and
hence the panels will “pop out” of the grid. Furthermore, the
ceiling panels will impact the grid system when they fall,
weakening the grid members.
5.2 Ceiling Perimeter Attachment Damage
Figure 15 shows minor damage observed at the
unattached joints between grid members and wall molding.
Figure 12 Vertical Acceleration in Panel (C9)
Versus Grid (C4) in (a) 4th Floor (Unbraced) and (b)
5th Floor (Braced) Ceiling Due to 3D-Superstition
Hills – Westmorland (TPB System)
Figure 15 Ceiling Perimeter Attachment
Failure after 3D-Northridge-Rinaldi (TPB
The mechanism is interpreted as follows: when the grid
member moved away from the wall, the grid member lost
contact with the wall molding (Figure 16(a)). Since the
middle slot is large relative to the screw dimensions, the grid
member may settle slightly due to vertical movement of the
grid member, rotation of the seismic clip over its attachment
point, or popping out of the middle screw (Figure 16(b)). As
the settled grid member moved back toward the wall, it hit
the wall molding to cause the observed damage (Figure
16(c)). This damage could perhaps be avoided by increasing
the seat length of the 22 mm (7/8 in) wall molding. Note that
ASTM E580/E580M-11ae1 (ASTM 2011) permits the use
of either 22-mm (7/8-in.) or 50-mm (2-in.) wall molding to
support seismic clips, and therefore, the tested design meets
code requirements.
Grid Move to the Right
Ceiling Grid
Middle Slot Screw
Small Settlement of Grid
Grid-Wall Molding Interaction
moment around the branch line is the summation of the
torque generated at each drop (Figure 17(b)). The current
code (NFPA 2011) permits the connections along this branch
line to be designed without torsional resistance since the
cumulative horizontal length of the unsupported armover
less than 610 mm (24 in). However, the torsional resistance
of the threaded joints was not sufficient to resist the
cumulative torsional demand generated in the large vertical
excitation, and permanent twisting of the branch line was
5.4 Damage Near Sprinkler Heads
Wherever rigid drop pipes were used, the sprinkler head
damaged the ceiling panels regardless of whether the
oversized gap configuration, which conforms to code
requirements (ASTM, 2011), or the no gap configuration
were used. Pounding of the sprinkler heads against the
ceiling panels produced damage to the ceiling panels even in
motions with moderate horizontal floor accelerations. As an
extreme example, a 200 mm (8 in) long piece was knocked
out of the ceiling panel during (2D -Tohoku- Iwanuma/base
fixed) (Figure 18(a)), which is much larger than the 50 mm
(2 in ) gap required by code. On the other hand, no damage
was observed around the flexible hose fittings that were
Wall Molding
ACM7 Seismic Clip
Figure 16 Grid - Wall Molding Interaction Mechanism
5.3 Permanent Rotation of Armover Drops
A vulnerability of armover drops compared to straight
drops was observed in these experiments. During
3D-Northridge-Rinaldi (TPB system), the entire 5th floor
Branch Line 1 with three armover drop pipes twisted around
its connection point to the main run (Figure 17(a)). Due to
vertical acceleration, a vertical inertia force is generated
proportional to the mass of the armover drop. The twisting
T = T1+T2+T3
Figure 17 (a) Armover Permanent Rotation after
3D-Northridge–Rinaldi (TPB System), and (b)
Torsional Demand on Armover Branch Line
Figure 18 Comparison of Observed Damage Near (a)
Conventional Sprinkler Head, and (b) Flexible Hose
Sprinkler Head after 2D-Tohoku-Iwanuma (Base Fixed)
mounted at the end of Branch Line 3 (Figure 18(b)).
5.4 Failure of the Pipe Hangers
Another response mode that was clearly observed
during the experience was formation of a gap between the
pipe and the hanger ring of the pipe hanger. The vibration
and subsequent pounding of the pipe against the hanger ring
led to failure of the hanger ring connection (Figure 19). This
behavior is probable in large vertical excitation, where the
pipe hanger threaded rod has not been detailed to extend
down to the pipe. Figure 20 depicts this failure that was
observed at two hangers near the riser pipe on both two
Pipe Hanger
demands (e.g. large vertical acceleration relative to
horizontal acceleration).
Hanger Ring
Generated Gap
Figure 19 Captured Frame from Recorded Movie that
Shows the Generated Gap Between Pipe and Hanger
Ring During 3D-Northridge–Rinaldi (TPB System)
Hanger Ring
Threaded Rod
This material is based upon work supported by the
National Science Foundation under Grant No. 0721399. Any
opinions, findings, conclusions or recommendations
expressed in this document are those of the investigators and
do not necessarily reflect the views of the sponsors. The
input provided by the Practice Committee of the NEES
Nonstructural Project, composed of W. Holmes (Chair), D.
Allen, D. Alvarez, and R. Fleming; by the Advisory Board,
composed of R. Bachman (Chair), S. Eder, R. Kirchner, E.
Miranda, W. Petak, S. Rose and C. Tokas; and by the other
members of the Experimental Group, A, Filiatrault, G.
Mosqueda, A. Reinhorn, and J. T. Hutchinson, has been
crucial for the completion of this research. The authors
recognize and thank the following companies for providing
product donations and technical support: USG Building
systems, Victaulic, Tolco, Hilti, Allan Automatic Sprinkler
and CEMCO steel.
Figure 20 Pipe Hanger Ring Failure after
3D-Northridge–Rinaldi (TPB System)
The major observations of this experiment are
summarized below.
 Use of lateral bracing including compression posts
may not improve the seismic response of ceiling,
especially if the system is subjected to strong
vertical excitation.
 Due to the twisting moment generated from the
armover drops, long branch line pipes with several
unsupported armover drops are expected to twist
around the branch line threaded connection point.
 The oversized gap configuration with 50 mm (2 in)
ring was not effective to prevent damage to ceiling
panels resulting from sprinkler head pounding;
however, the use of flexible hose drops
substantially reduced the piping-ceiling interaction.
 The pounding of the pipe against the hanger ring in
vertical excitation led to failure of the hanger ring
 These observed response mechanisms may be
sensitive to specific circumstances of the
experiments, such as building configuration (e.g.
slab vibration characteristics) and acceleration
ASTM E580/E580M-11ae1. (2011). “Standard Practice for
Installation of Ceiling Suspension Systems for Acoustical Tile
and Lay-in Panels in Areas Subject to Earthquake Ground
Motions.” ASTM International, Volume 04.06.
ATC. (2007). FEMA 461-Interim protocols for determining seismic
performance characteristics of structural and nonstructural
components through laboratory testing. Redwood City, CA.
Ayres, J.M., Phillips, R.J. (1998).“Water Damage in Hospitals
Resulting from the Northridge Earthquake.” ASHRAE Trans.,
Vol. 104, Part 1, American Society of Heating, Refrigerating and
Air-Conditioning Engineers, Atlanta, Georgia.
Kircher, C. A. (2003). “It Makes Dollars and Sense to Improve
Nonstructural System Performance.” ATC-29-2 Proceedings of
Seminar on Seismic Design, Performance, and Retrofit of
Nonstructural Components in Critical Facilities.
Kasai, K., et al. (2010). “Full scale shake table tests of 5-story steel
building with various dampers.” Proc., 7th Intern. Conf. on
Urban Earthquake Engin. & 5th
Intern. Conf. on
Earthquake Engin. Tokyo Inst. Tech., Tokyo, Japan.
NFPA13. (2011). "Standard for the Installation of Sprinkler
Systems." National Fire Protection Association, 2010 Edition,
Quincy, MA.
Ryan, K., Dao, N, Sato, E., Sasaki, T., and Okazaki, T. (2012)
“Aspects of Isolation Device Behavior Observed from
Full-Scale Testing of an Isolated Building at E-Defense.” 43rd
Structures Congress, ASCE, Chicago, USA.
Zaghi, A. E., Maragakis, E. M., Itani, A., and Goodwin, E. (2012).
“Experimental and Analytical Studies of Hospital Piping
Subassemblies Subjected to Seismic Loading.” Earthquake
Spectra, EERI. 26(1), EERI
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