SEFC 2015 PROCEEDINGS Structural Engineering Frontier Conference, March 18-19, 2015

SEFC 2015 PROCEEDINGS Structural Engineering Frontier Conference, March 18-19, 2015
SEFC 2015 PROCEEDINGS
Structural Engineering Frontier Conference, March 18-19, 2015
Tokyo Institute of Technology, Yokohama, Japan
NUMERICAL SIMULATION OF THE PERFORMANCE OF INTEGRATED CEILING-SPRINKLER
SYSTEMS
Siavash Soroushian 1) and Emmanuel "Manos" Maragakis 2)
1) Research Scientist, Department of Civil and Environmental Engineering, University of Nevada, Reno, USA
2) Professor, Dean of Engineering, University of Nevada, Reno, USA
[email protected], [email protected]
Abstract: Suspended ceiling and fire sprinkler piping systems are one of the most vulnerable types of
nonstructural systems that have suffered costly damage during past earthquakes. The seismic performance
of these two systems are poorly understood due to their heterogeneous nature. In order to fill this
technical gap, a numerical modeling methodology is proposed for the integrated ceiling and sprinkler (CP)
systems using the OpenSees software. This numerical simulation incorporates several experimentally
calibrated component models for the pipe and ceiling joints as well as the supporting elements (e.g.
braces, hangers) of CP systems. The propagation of seismic damage in CP systems and falling of ceiling
panels are accounted for by using an element removal algorithm. The modeling technique is then
validated using the experimental results of a CP system installed in a full-scale five-story building. The
modeling method proved to be successful in predicting the pattern and location of failure in these
systems.
Keywords: earthquake responses, non-structural components, suspended ceiling system, fire sprinkler
piping system, numerical simulation, full scale experiment
1.INTRODUCTION
Damage to nonstructural components in a building is
usually triggered at shake intensities much lower than those
required to initiate structural damage (Taghavi and Miranda,
2003). Also, damage to these components accounts for the
major portion of national annualized earthquake losses
(FEMA E-74, 2011). Among these nonstructural systems,
suspended ceiling and fire sprinkler systems are known as
one of the main source of losses after an earthquake
(Echevarria et al., 2012).
Several failure modes such as falling of ceiling panels,
buckling of ceiling grid members, failure of ceiling grid
connections, damage near the ceiling perimeter, leakage of
pipe joints, impact of sprinkler heads and ceiling panels, and
failure of supporting elements were identified in sprinkler
and ceiling systems. Nearly all of these damage mechanisms
were observed in past earthquakes such as the 1989 Loma
Prieta Earthquake, 1994 Northridge Earthquake, 2006
Hawaii Earthquake, 2010 Chile Earthquake, 2010 Haiti
Earthquake, and 2011 Christchurch (New Zealand)
earthquake (Soroushian et al., 2014a).
Despite several experimental studies (e.g. ANCO, 1983;
Zaghi et al., 2012; Soroushian et al., 2012; Ryu and
Reinhorn, 2013; Gilani et al., 2013; Rahmanishamsi et al.,
2014), very few analytical works (e.g. Echevarria et al., 2012;
Ryu et al., 2012; Soroushian et al., 2013, 2014b) were
performed on ceiling and piping systems. The lack of
analytical studies on ceiling and piping systems was due to
the complexity of these systems. Also, the oversimplified
previous numerical studies were found to be unreliable and
full-scale
experiments
were
generally
preferred
(Badillo-Almarez et al., 2006). In order to fill this significant
technical gap, this study aims to propose an experimentally
validated analytical model of integrated sprinkler and ceiling
systems.
In the course of this project, 150 monotonic and reverse
cyclic tests were conducted on different ceiling components,
including grid connections, perimeter attachments and
supporting elements. A series of nonlinear models were
developed for the ceiling components using the experimental
data. The previously developed nonlinear hinge models were
used for the fire sprinkler pipe joints. These ceiling and
piping component models were then incorporated in an
OpenSees model of a ceiling-sprinkler assembly that was
tested at the E-Defense shake table facility in 2011. In this
paper, a brief description of ceiling and piping systems along
with their modeling methodology is presented. Then, a
summary of experimental setup and input excitations is
given. Finally, the results from the analytical simulation
were compared to the experimental results.
provide the necessary pressure to spray an area in the event
of fire or smoke. Pipe runs are composed of: 1) risers:
vertical supply pipes; 2) main runs: pipes that supply branch
line; 3) branch lines: feed drop pipes; and 4) drops: armover
or straight drops that supply the sprinkler head. All threaded
rod hangers carry the dead weight of a piping system. Braces
resist the seismic load of a piping system and can be solid or
tension-only (cable) braces. Wire restrainers limit the
displacement movement of branch lines.
3. ANALYTICAL MODELS OF CEILING AND
SPRINKLER COMPONENTS
The analytical models of pipe joints and pipe supporting
elements (hangers and braces) were borrowed from the
previous studies, which will be discussed in following
sections. However, the analytical models of ceiling
components were developed and calibrated by a series of
cyclic and monotonic experiments was performed at
University of Nevada, Reno. These tests included axial,
shear, and bending tests of grid connections, perimeter
attachments, interaction of ceiling panels and sprinkler heads,
and ceiling hangers (see Fig.1). Several failure modes were
identified. Force-displacement responses and capacity
fragility curves were developed as part of these experiments.
A detailed description and major findings of these
experiments can be found in Soroushian et al. (2014 c-f).
2.SUSPENDED CEILING AND PIPING SYSTEMS
Suspended ceiling systems are a nonstructural component
installed within buildings to serve as an aesthetic barrier
between electrical, mechanical, and piping systems and the
living space below. The entire ceiling grid is hung from the
structural floor above. A typical suspended ceiling system
with acoustic tiles is composed of grid members, boundary
wall molding, hanger splay wires, and, if braced, splay wire
braces and compression posts. The grid system of a
suspended ceiling system consists of inverted main tee
beams and inverted cross tee beams, made of light-gauge
steel, that interlock at locations of intersection. The grid sits
on light-gauged L-shaped wall molding at its perimeter that
is screwed to the partition walls. A ceiling system in a low
seismic zone has a minimum 10-mm grid wall molding
clearance on all boundaries. The perimeter conditions of a
seismically braced ceiling system are slightly different, with
a minimum grid wall molding clearance of 19mm on two
adjacent boundaries and fixed to the wall along the other two
boundaries.
Acoustic ceiling tiles are manufactured from a
compressed high-density mineral fiber material and are
available in many shapes and sizes. The simplest tile
geometry is a 0.6-m x 0.6-m square with a thickness ranging
from 13mm to 19mm. The acoustic tiles are placed within
the tee beam grid system, simply resting on the flange of
each tee beam. The tiles are not mechanically locked into
place. Hanger wires are placed at 1.2-m intervals around the
ceiling perimeter at no more than 8in. from the wall. The
compression post and splay wire bracing is installed at 3.7-m
intervals beginning 1.8m from the wall. A compression post
is used in a bracing assembly to react against the vertical
component of the splay wire braces. The hanger wires and
splay wires of braced systems are made of 12-gauge wire
that is looped through holes in main tee beams and
connected to the supporting floor deck above the ceiling.
A fire sprinkler system is a network of water pipes
supplied by water sources with sprinkler heads fitted at
recommended spacing. A typical fire sprinkler piping system
is composed of a water pressure tank, pipe runs, sprinkler
heads, hangers, braces, and restrainers. Pressure tanks
Axial
Shear
Perimeter
Bending
Panel-Sprinkler
Hanger
Fig. 1: Test Setups of Different Ceiling Component
Experiments
The experimental data from the component tests was
utilized to develop analytical models of these components
using OpenSees analytical software (OpenSees, 2013). The
“Pinching4” uniaxial material along with a “zeroLength”
2
element was used to simulate the hysteresis behavior of
ceiling joints and perimeter attachments. The “Pinching4”
material enables the simulation of complex pinched force
hysteresis responses by accounting for degradations under
cyclic loadings. This material model requires the definition
of 39 parameters. A detailed description of these parameters
can be found in the OpenSees Manual (OpenSees, 2013). A
bilinear material model that incorporated the initial gap was
adopted as the constitutive model of the ceiling hanger, wire
bracing, and panel-sprinkler interaction. This material is
implemented in OpenSees as an Elastic Perfectly Plastic Gap
(EPPG) material. The EPPG material model can capture
either compression or tension behavior. The material
behavior is controlled by: 1) initial module of elasticity
(stiffness), E (k); 2) yield stress (force), σy (Fy); 3) initial gap
strain (displacement); 4) post-yield stiffness ratio, b = Ep/E;
and 5) damage type, which is an optional parameter to
specify whether to accumulate damage or not in the material
model. Truss and “zeroLength” elements were used for the
modeling of wires and panel-sprinkler interactions,
respectively.
For calibration, a set of parameters was determined for
each experiment of a component. For the simplicity of
modeling suspended ceiling systems, one suite of material
parameters was defined for each component as the generic
(representative) parameters, called the generic model. To
develop this model, the median values of all specimens for
each parameter were calculated. Examples of the
comparisons between sample experimental results and the
responses obtained from the generic model are presented in
2ft. Cross Tee-Axial
1.8
Experimental
4ft. Cross Tee-Shear
0.9
Force (kN)
1.8
0.9
0.0
Roof
0.0
3
-0.9
-0.9
-1.8
-5
-3
0
3
Displacement (mm)
-1.8
-25
5
2ft. Cross Tee-Perimeter
Moment (kN-mm)
0.0
Force (kN)
-13
0
13
Displacement (mm)
2ft. Cross Tee-Bending
3
25
16 3
68
0.4
-0.4
-0.9
-1.3
-25
0.08
0.08
-13 Panel-Sprinkler
0
13
Displacement (mm)
3
23
Panel-Sprinkler
-0.1
0
0.1
Rotation (rad.)
0.00 0
00
0
2nd fl.
5
Experimental Panel 1
1.8
Experimental Panel 12
Experimental Panel 23
Experimental Panel 34
0.9
Experimental Panel 45
Experimental
Panel 5
data6
Analytical-Generic
data6
0.0
data8
0.5 Analytical-Generic
1
1.5
2
2.5
0
25Displacement
51(in.)
76 3
data8
0.5
1
1.5 (mm)
2
2.5
3
Displacement
Displacement (in.)
7
0.2
5
5
23
Hangers
Force (kN)
0.02
10
12
10
2.7
0.1
0.02
3rd fl.
1st fl.
Dimensions are in meter
Fig. 3: Views and Dimensions of Building Specimen
0.3
0.04
0.04
0.2
5
4
-23
Panel-Sprinkler
0.06
0.06
4th fl.
0
-45
-0.2
25
5th fl.
45
0.4
Force
(kN)
Force
(kips)
Force
(kips)
4th floor
5th floor
Analytical-Generic
2.7
Force (kN)
Fig. 2.
4.VERIFICATION OF A CEILING PIPING (CP)
MODEL WITH A FULL-SCALE EXPERIMENT
4.1 Test Setup
A collaborative research program on base-isolated
buildings was conducted under the Memorandum of
Understanding between the National Institute of Earth
Science and Disaster Prevention (NIED) of Japan and the
National Science Foundation (NSF) George Brown Jr.
Network for Earthquake Engineering Simulation (NEES)
program of the U.S. As part of these shake table tests
performed on a full-scale five-story moment frame, the
“NEESR-GC: Simulation of the Seismic Performance of
Nonstructural Systems” was commissioned to complement
the
experiments
by
adding
an
integrated
partition-ceiling-sprinkler piping system on the fourth and
fifth floors of the five-story building. This structure was
approximately 16-m tall and asymmetric in plan with
dimensions of 10m by 12m (2 bays by 2 bays). The overall
views and dimensions of building specimen are shown in Fig.
3. Further information about the building itself is provided in
Dao (2012) and Ryan et al. (2013).
Standard Schedule-40 pipes were used per NFPA 13
(NFPA, 2011) for the fire sprinkler system. The piping
system included one 76-mm-diameter riser pipe, one
64-mm-diameter main run (East-West) and three
(North-South) 32-mm- and 25-mm-diameter branch lines
(Fig. 4). The connections of the riser with the main run and
Experimental-Wire1
Experimental-Wire2
Experimental-Wire3
Analytical-Generic
13
25
Displacement (mm)
38
Fig. 2: Comparisons between Experimental Results and
Analytical Responses
3
the main runs to the branch lines were grooved-fit
connections. The remaining connections were threaded
fittings. Branch Lines 1 and 2 each fed three 305-mm-long
sprinkler drops (Fig. 4). Branch Lines 1 and 2 incorporated
armover drops (Γ-shape drops) and straight drops,
respectively. A Victaulic Aquaflex (Victaulic, 2008) flexible
hose drop was used at Drop 2 on Branch Line 3. The ends of
the branch lines were restrained with two diagonal 12-gauge
splay wires to limit the lateral movement. Additional
in-plane support was provided by inclined 25-mm-diameter
pipes for longitudinal and transverse sway braces on the
main run near the riser. A transverse solid brace was also
used at the end of the main run. Two solid braces were used
to restrain the end of the riser pipe below the fourth floor.
A lay-in-tile suspended ceiling system of approximately
84m2 was designed for each floor that worked around
existing boundaries (Fig. 4). However, the ceiling area was
interrupted at two locations (total area of 3m2) by vertical
trusses used to measure story drifts. The ceilings were
installed in the test frame per ASTM E580/E580M-11ae1
standards (ASTM, 2011). The grid was constructed using the
heavy-duty USG DONN 24-mm exposed tee system. Main
runs and cross tees were aligned as shown in Fig. 4. The
main runs were supported by 12-gauge Hilti X-CW
suspension wires spaced at 1.2m; additional wires supporting
all perimeter grid pieces were placed within 203mm of the
partition wall faces. The plenum height -- the distance
between the bottom of the structural slab and the ceiling
system -- was 0.9m. A 22-mm wall molding was attached to
the perimeter partition walls.
On the North and East sides, the main runs and cross tees
were attached tightly to the wall molding using USG/ACM7
seismic clips with one partition-attached screw and one top
hole screw to prevent movement of the ceiling grids. On the
South and West sides, a 19-mm clearance was provided
between the main runs/cross tees and the wall molding. This
connection used 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. At the hatched areas in Fig. 4,
heavier gypsum board panels were used to simulate the
weight of light fixtures. In order to compare the behavior of
braced and unbraced ceiling systems, the seismic braces
were only installed on the fifth floor ceiling while all other
details were identical on both floors. Each seismic brace
consisted of: 1) a system of splay wires and 2) a
USG/VSA30/40 compression post. The seismic braces were
placed at 3.7m on center, in each direction, with the first set
occurring within 1.8m of the wall face. Four wires splayed at
90° from each other were attached to the main run within
51mm of the compression post. Due to the connection
constraints, steel stud compression posts were used instead
of VSA30/40 compression posts when the posts were
attached to structural girders. In one location on each floor, a
two-way steel stud rigid brace was used in place of two of
the splay wires due to space constraints.
Fig. 4: Plan Views of Ceiling and Piping Systems
4.2 Modeling Methodology
The analytical model of an integrated suspended ceiling
and piping system was created using OpenSees (OpenSees,
2013). All pipe runs were modeled with elastic “Force-Based
Beam-Column” (OpenSees, 2013) elements with gross
section properties of the pipes. Two different inelastic
moment-rotation models, developed and validated by
Soroushian et al. (2013, 2014b) for threaded and grooved
fittings, were assigned to the rotational degrees of freedom at
piping joints. These inelastic models are based on
“Pinching4" material
and are able to simulate the
hysteresis response of piping joints of varying diameters.
The hanger rods were modeled using nonlinear
“Force-Based Beam-Column” elements with a fiber section
consisting of the Giuffre-Menegotto-Pinto steel material
(CEB, 1996). A modulus of elasticity of 149,000MPa, yield
strength of 441MPa, and hardening slope ratio of 0.01%
4
“zeroLengthImpact3D” element with a 19-mm gap was used
for connecting grids and wall angles in the sliding direction
of unattached perimeters. A horizontal friction coefficient of
0.5 was assumed for all of the “zeroLengthImpact3D”
elements based on calibration of the analytical model with
experimental data.
The interaction between the ceiling panels and sprinkler
heads was modeled using one "zeroLength" element between
each sprinkler head node and center panel node. Two parallel
inelastic force-displacement models (one in tension and one
in compression), developed and validated by Soroushian et
al. (2014e) based on ceiling panel tearing tests, were
assigned to the translational degrees of freedom at these
elements.
These
inelastic
models
utilized
the
"Elastic-Perfectly Plastic (EPP) Gap" material and are able
to simulate the initial gap between ceiling panels and
sprinkler heads based on different diameters of oversized
holes. A modulus of elasticity of 2.5MPa and a strength of
0.4MPa (-0.4MPa for tension) with various initial gaps were
used for defining these EPP materials.
The real-time element removal algorithm was
incorporated in the analyses to capture the progression of
damage to the piping and ceiling systems during seismic
excitations. The element removal algorithm enables the
model to redistribute the forces after failure of an element
using the "remove element" command in OpenSees (2013).
This algorithm was set to remove the pipe wire restrainers
after reaching their failure capacity, 1.8kN from USG (2006).
During the response history analyses the program triggered
the "remove element" command when the axial force of a
were assigned to the hangers based on experimental data
(Soroushian et al., 2014b). The hanger rods had a pin
connection to the pipes and were assigned a fixed boundary
at their other end. The wire restrainers were modeled with
"truss" elements with a tension only "Elastic-Perfectly
Plastic (EPP) Gap" material with a modulus of elasticity of
200,000MPa and a tensile strength of 690MPa (Soroushian
et al., 2014b). The rigid seismic braces were modeled with
elastic “Force-Based Beam-Column” elements. The
connections of the seismic braces were assumed to be rigid
at both ends. The mass of the piping system was determined
based on the wet weight of pipes. An additional mass of
0.5lb was considered for each sprinkler head. The mass and
the weight of the system were concentrated at the nodal
points.
All ceiling grids were modeled with elastic “Force-Based
Beam-Column” (OpenSees, 2013) elements with gross
section properties of the main runs and cross tees. The main
runs were assumed to be continuous while inelastic axial,
shear, and bending models, developed as discussed in the
previous section, were used at each end of the cross tees. The
0.6-m x 0.6-m acoustic ceiling tiles were modeled with an
x-shape assembly with five lumped masses placed at the
center and four corners of this assembly. The weight of the
ceiling tiles was obtained from the experiment and was equal
to 3.5kg/m2. The same modeling assumptions used for
piping wire restrainers were used for 12-gauge ceiling
hanger and brace wires. Compression posts were modeled
with elastic “Force-Based Beam-Column” (OpenSees, 2013)
elements with gross section properties of these members.
The connections between each corner of the ceiling panels
and grid intersections were modeled using three
“zeroLengthImpact3D” elements (OpenSees, 2013). Two of
these elements were oriented perpendicularly in a horizontal
direction. These horizontal elements accounted for the
32-mm gap between the ceiling panels and grid boundaries if
the panels are perfectly centered. These elements also
account for impact between panels and grids when a panel’s
displacement reaches 32mm in any direction relative to the
ceiling grids. The vertical element with no initial gap allows
tile uplift relative to the grid plane. In the vertical direction,
additional “zeroLength” elements with “Elastic” uniaxial
material were used between each corner of the ceiling panels
and grid intersections to capture the panel-grid vertical
interaction. A stiffness of 35kg/m was considered for these
elements, which was obtained from the component level
tests at the University of Nevada, Reno. The stiffness value
was increased to 70kg/m for perimeter and corner panels due
to additional resistance from seismic clips and hangers. Grid
members are attached to the perimeters using the inelastic
hinge model presented in previous sections, while they are
free to slide in the floating perimeter side. Also, a horizontal
a) Panels
d1 >1.5 in.
or
d1 >1 in.
d2 > 0.125
in.
b) 0.6m Cross Tee
0.6m
0.6m
Main
Runner
0.6m
Cross Tee
0.6m
0.6m
1.2m
1.2m
c) 1.2m Cross Tee
0.6m
0.6m
1.2m
Cross Tee
0.6m
0.6m
1.2m
1.2m
Intact Joints
Failed Joints
Fig. 5: Remove Element Failure Mechanisms
5
pipe hanger reached five times the recorded axial force plus
1.1kN (NFPA13, 2011). The removal algorithm was set to
remove the solid braces after they reached their design
capacity, 28kN (NFPA13, 2011).
Ceiling grid connections and their perimeter attachments
were removed during the response history analysis when
they reached their failure capacities obtained from the
experiments discussed in previous sections. Ceiling hangers
and wire braces were removed when their axial forces
reached 0.4kN and 1.1kN (ASTM, 2011), respectively.
Ceiling panels were removed when the uplift of at least one
tile corner reached the grid height and the horizontal gap at
the uplifted corner is closed (see Fig. 5a). When the both
ends of a 0.6-m cross tee reach their failure capacity, the
corresponding grid and its supporting panels are then
removed from the model (Fig. 5b). Four panels and two
0.6-m cross tees are removed from the model if similar
failure mechanisms happens for a 1.2-m cross tee (Fig. 5c).
4.3 Input Motion
The five-story building was subjected to several ground
motions over six days of experiments in three base
configurations: 1)triple pendulum isolated (TPB), 2) lead
rubber isolated (LRB-CLB), and 3) fixed-base. Out of 41
total shaking table excitations, 23 were triaxial (included a
vertical component), and the remaining tests were performed
using biaxial horizontal excitation. In this study, the seismic
performance of the ceiling and piping systems subjected to
the simulated Northridge-Rinaldi motion in a fixed-base
structure was selected to calibrate the analytical model. Two
different intensities of motions as: 1) horizontal-only motion
with 35% scale factor (RRS35XY) and 2) 3D motion with
target scale factors of 35% and 88% (RRS35XY-88Z) in
horizontal and vertical directions, respectively. Input
motions were applied to the ceiling and piping systems using
multiple support excitation, which requires input
displacement histories at attachment points. To do so, a
wavelet de-noising method was used to obtain the floor
displacement histories from the available floor acceleration
records. The displacement histories (X and Y) calculated at
the geometric center of the floors were considered to be the
input motions in horizontal directions. However, the input
vertical displacement histories varied from a point close to
the column to a point at the center of the slab (Sorushian et
al., 2014g) by using a curve fitting approach (see Fig. 6a).
Three components of 3D input excitations at the center of
SlabSE are presented in Fig. 6.
4.4 Validation of the Analytical Model
The modeling of suspended ceiling and fire sprinkler
piping systems in OpenSees followed a similar procedure to
those presented in the previous sections. The displacement,
acceleration history, and spectral responses of the analytical
models of ceiling and sprinkler systems were compared with
SlabSE
SlabNE
SlabNW
1
2ft. Cross Tee-Axial
0
-1
2.7
-2
5
1.8
Analytical-Generic
Experimental
10
Force (kN)
Acceleration (g)
2
15
20
Time (sec.)
Roof Floor
25
5th Floor
E-W
0
-25
0
13
-25
0
13
10
20
30
N-S
30
10
20
V
30
-13
0
3
-0.9
0
-1.8
-5
-51
5
10
20
-3
30
0
Time (sec.)
15
-3
0
3
Displacement
(mm)
20
Time(sec)
10
20
30
V
0
10
0.0
51
0
0
-5
0
20
N-S
0
-13
0
5
10
102
Spectral Acc. (g)
Displacement (cm)
E-W
0
Displacement(mm)
25
0.9
10
20
30
Fig. 6: Example of Calculated Displacement Input Motion
from RRS35XY-88Z Excitation
4
2
0
0
0.5
1
1.5
2
Period, T (sec.)
2.5
3
Fig. 7: Comparison of experimental and analytical response
of the piping system under RRS35XY
6
experimental results. In this study, comparison between the
analytical and experimental horizontal responses of piping
and ceiling systems were compared under RRS35XY, which
was limited to the components installed in the fifth floor.
Also, the pattern of failed ceiling panels in braced and
unbraced ceiling panels was investigated during the
RRS35XY-88Z excitation. Figures 7 and 8 show that the
analytical model cannot predict every detail of the response,
but it can predict the trend of the response very well.
by analytical models. However, the pattern and location of
the damaged parts were predicted well by the analytical
models. It should be also noted that the presented analytical
model does have limitations, which are under investigation
by the authors.
4.5 Case Study Example: Unbraced versus Braced
Ceiling System
The use of seismic bracing in ceiling systems has been a
topic of concern for more than a two decades (e.g. ANCO,
1983; Soroushian et al., 2012; Ryu and Reinhorn, 2013;
Rahmanishamsi et al., 2014). While in general seismic
braces are known as an effective solution to reduce ceiling
damage, several factors, such as the size of the ceiling, the
type of braces, shake intensities, and supporting slab
dynamic properties, may result in the opposite performance.
In this study, the seismic performance of braced and
unbraced ceilings were compared under the RRS35XY-88Z
excitation. The analytical model of each type of ceiling was
subjected to both 5th and floor motions. As shown in Fig. 10,
seismic braces did not have a significant effect on the pattern
of fallen ceiling panels. Also, the number of fallen ceiling
panels was less in unbraced ceiling systems compared to
braced ceiling systems in the previously mentioned case
2ft. Cross Tee-Axial
2
Analytical-Generic
Acceleration (g)
Force (kN)
2.7
Experimental
1
1.8
0
0.9
-1
-2
0.0
5
6
7
8
9
10
11
Time (sec.)
12
13
14
15
Displacement (mm)
-0.91.3
-1.8
-5
-3
0
3
Displacement (mm)
0
-1.3
5
5
10
15
20
Time (sec.)
Spectral Acc. (g)
4
3
2
5th Floor
5th Floor
Braced
Ceiling
Unbraced
Ceiling
1
0
0
0.5
1
Period, T (sec.)
1.5
2
Fig. 8: Comparison of Experimental and Analytical
Response of the Ceiling System under RRS35XY
As shown in Fig. 9, in both braced and unbraced ceiling
systems, the number of failed ceiling panels is overestimated
Experimental
Analytical
Unbraced
Ceiling
Unbraced
Ceiling
Roof Floor
Roof Floor
Braced
Ceiling
Unbraced
Ceiling
In-place ceiling panels
Experimental
Analytical
Braced
Ceiling
Braced
Ceiling
Fallen ceiling panels
Fig. 10: Comparison of Analytical Pattern of Fallen Ceiling
Panels in Braced and Unbraced Ceiling Systems under
RRS35XY-88Z
study.
5. SUMMARY AND CONCLUSION
In-place ceiling panels
A series of monotonic and reverse cyclic tests were
conducted on different ceiling components, including grid
connections, perimeter attachments, and supporting elements.
Several nonlinear models were developed for the ceiling
components using the experimental data. The previously
developed nonlinear hinge models were used for the fire
Misaligned ceiling panels
Fallen ceiling panels
Fig. 9: Comparison of Experimental and Analytical Pattern
of Fallen Ceiling Panels under RRS35XY-88Z
7
sprinkler pipe joints. These ceiling and piping component
models were then incorporated in an OpenSees model of a
ceiling-sprinkler assembly that was tested at the E-Defense
shake table facility in 2011. In this paper, the pattern of
failed ceiling panels in braced and unbraced ceiling systems
developed from the analytical simulation was compared with
the experimental observation. While the pattern and location
of the damaged parts were predicted well by the analytical
models, the number of failed ceiling panels is overestimated
by analytical models. The analytical model presented here
does have limitations, which are under investigation by the
authors.
Echevarria, A., Zaghi, A. E., Soroushian, S., and Maragakis,
M. (2012). “Seismic Fragility of Suspended Ceiling
Systems”,
15th
World
Conference
on
Earthquake
Engineering (15WCEE), Lisbon, Portugal.
FEMA E-74 (Federal Emergency Management Agency),
(2011). “Reducing the Risks of Nonstructural Earthquake
Damage: A Practical Guide”, Redwood City, CA.
Gilani, A. SJ., Takhirov, S., and Tedesco, L., (2013).
“Seismic Evaluation of Suspended Ceiling Systems Using
Static and Dynamic Procedures”, ASCE/SEI Structures
Congress, Pittsburg, PA.
NFPA13 (2011). “Standard for the Installation of Sprinkler
Acknowledgements
This material is based upon work supported by the
National Science Foundation under Grant No. 0721399. This
Grand Challenge (GC) project to study the seismic response
of nonstructural systems is under the direction of M.
Maragakis from the University of Nevada, Reno and Co-PIs:
T. Hutchinson (UCSD), A. Filiatrault (UB), S. French (G.
Tech), and B. Reitherman (CUREE). 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, has been crucial for the completion of this research.
Systems.” National Fire Protection Association, 2010
Edition, Quincy, MA.
Open System for Earthquake Engineering Simulation
(OpenSees)
website,
http://www.opensees.berkeley.edu
(2013):
.
PEER,
Berkeley:
University of California
Rahmanishamsi, E., Soroushian, S., Maragakis, M., (2014)
“Seismic Response of Ceiling/Piping/Partition Systems in
NEESR-GC
System-level
Experiments”,
ASCE/SEI
Structures Congress, Boston, MA.
Ryan, K. L., Coria, C. B., Dao, N.D. (2013). “Large scale
earthquake simulation of a hybrid lead rubber isolation
system designed with consideration of nuclear seismicity”,
CCEER Report No. 13-09. Center for Civil Engineering
Research, University of Nevada, Reno.
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9
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