7th International Conference on
Protection of Structures against Hazards
30-31 October 2018, Hanoi, Vietnam

MOTION ANALYSIS OF EARTHQUAKE-RESISTANT AND
NON-RESISTANT CEILINGS UNDER SEISMIC EXCITATION
Kotoku Maeda*, Takuzo Yamashita† and Daigoro Isobe‡*

Graduate School, University of Tsukuba
1-1-1 Tennodai, Tsukuba-shi, Ibaraki 305-8573, Japane-mail: <s1720973@s.tsukuba.ac.jp>

Keywords: Ceiling collapse, gymnasium ceiling, earthquake-resistant measures,
Adaptively shifted integration (ASI) - Gauss technique, motion analysis, finite element
methodAbstract. As buildings with large-scale spaces such as school gymnasiums areused as refuge bases during earthquakes, they are required to be subsequently
usable and to resist aftershocks. However, in the 2011 Great East Japan
Earthquake, cases had been reported in which gymnasiums did not satisfy thisfunction as refuge bases owing to fallen ceilings and lightings. Therefore,
measures to prevent ceilings from falling must be considered; in order to achieve
that, it is necessary, first, to understand the collapse mechanisms of the ceilings.
In this study, the difference in behaviors under seismic excitations is
confirmed via several motion analyses of earthquake-resistant and non-resistantceilings. Two types of numerical models representing the ceilings are constructed.
The non-resistant ceiling is composed of hanging bolts, ceiling joist receivers,
ceiling joists and plaster boards. The components are connected with metal
fittings. For example, hanging bolts and ceiling joist receivers are connected withhangers, and ceiling joist receivers and ceiling joists are connected with clips.
Furthermore, ceiling joists and plaster boards are connected with screws.
Meanwhile, the earthquake-resistant ceiling is supported with additional braces tosuppress the motion. Clearance is provided between the ceiling and the sidewalls. Furthermore, clips used for the earthquake-resistant ceilings have stronger
connections than those used for non-resistant ceilings. For the numerical analysis,
all the members are modeled using linear Timoshenko beam elements, and theadaptively shifted integration (ASI) - Gauss code is applied. The detachment andcollapse of the ceilings are considered by introducing detachment conditions into
the metal fittings that were obtained from preliminary tests.
†

National Research Institute for Earth Science and Disaster Resilience‡ University of Tsukuba

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

Simulation is performed by applying a seismic wave, observed during the 2011
Great East Japan Earthquake, to the ceiling models. According to the numericalresults, the non-resistant ceilings sway greatly and collide with the walls. The
metal fittings detach occasionally during the impact. The ceilings collapse at theparts where numerous metal fittings detach. Meanwhile, none of the metal fittings
detach and the ceilings are safely installed in the case of the earthquake-resistantceilings.
1

INTRODUCTION

As buildings with large-scale spaces such as school gymnasiums are used as refuge bases
during earthquakes, they are required to be subsequently usable, and to resist aftershocks. In the2011 Great East Japan Earthquake, aftershocks of seismic intensity 6 or more occurred multiple
times following the main shock with a maximum seismic intensity of 7. Cases had been reported
in which gymnasiums did not satisfy the function as refuge bases owing to fallen ceilings andlightings (Figure 1)1. Because of numerous damages related to the ceilings, the Building Standard
Law was revised after the 2011 Great East Japan Earthquake2,3.
According to the new Building Standard4, "a ceiling over 6 m high, with a projected area ofmore than 200 m2, and a unit area weight of more than 2 kg/m2, installed in places of daily use" isdefined as "a ceiling that may cause serious harm." Measures to prevent these ceilings fromfalling should be performed. To apply effective earthquake-resistant measures, it is necessary tounderstand the collapse mechanisms of the ceilings. Recently, experiments on the collapse
damage of suspended ceilings were conducted at the E-Defense shaking table facility in 20145.
Experiments with two types of ceilings were conducted. One was a ceiling that was not provided
with measures to prevent a collapse. The other was a ceiling that was subjected to collapse
prevention measures based on building standards. In the experiment where a non-resistantceiling was installed, the collapse mechanism of the ceilings was investigated. In the experimentswith earthquake-resistant ceilings, the seismic resistance behavior of the ceiling was investigated.
Useful knowledge was gained through these experiments. However, detailed investigation undervarious conditions is required to obtain more general findings on the collapse mechanisms ofceilings because the ceilings used in facilities have various kinds of shapes and characteristics.
Meanwhile, it is typically costly to perform large-scale experiments repeatedly under various
conditions.
The purpose of this research is to investigate the motion behaviors of non-resistant ceilingsand earthquake-resistant ceilings under seismic excitation using numerical simulations, where theconditions and parameters can be easily changed, and to obtain the findings to clarify themechanisms of collapse and damage. We used the adaptively shifted integration (ASI) - Gauss
code6,7,8 that can stably perform highly nonlinear analysis including seismic motion, elastoplasticity and fracture.

Figure 1: Ceiling collapse that occurred during the 2011 Great East Japan Earthquake1

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

2

OUTLINE OF GYMNASIUM CEILING

In gymnasiums, ceilings with steel furrings are generally installed (Figure 2). The ceilings arecomposed of hanging bolts, ceiling joist receivers, ceiling joists and plaster boards. The
components are connected with metal fittings. For example, hanging bolts and ceiling joist
receivers are connected with hangers, and ceiling joist receivers and ceiling joists are connectedwith clips. Furthermore, ceiling joists and plaster boards are connected with screws.
In this study, we focused on two types of ceilings used in the experiments conducted by EDefense. Table 1 shows the specifications of a non-resistant ceiling without specific earthquakeresistant measures and an earthquake-resistant ceiling with several measures to prevent instantdetachments.
The length of all the hanging bolts in the non-resistant ceiling is 1.5 m such that the slope ofthe ceilings is the same as that of the roof of the gymnasium. Besides, the lengths of the hanging
bolts are required to be uniform in the new building standards. Therefore, the earthquakeresistant ceiling is also slanted with the same slope as that of the roof (Figure 3).
Herein, different points between the non-resistant ceiling and the earthquake-resistant ceilingare described. First, the spacing of the hanging bolts of the non-resistant ceiling is 1,000 mm 
1,147 mm, whereas that of the earthquake-resistant ceiling is 1,000 mm  860 mm. Clips thatconnect the ceiling joist receivers and the ceiling joists are also different. The clips used in theearthquake-resistant ceiling are attached between the joists and receivers with screws, and arestronger than the clips used in the non-resistant ceiling, which are simply bended and attached to
the receivers (Figure 4). Furthermore, some braces are additionally installed in the earthquakeresistant ceilings. In addition, there is no clearance in the non-resistant ceilings, but theearthquake-resistant ceilings have a clearance of 60 mm beside the wall.

：Joint metal： Constituent member

Hanging bolt

Ceiling joist joint
HangerCeiling joist
receiver

Ceiling joist
Clip

Plaster board

Screw

Figure 2: Components of conventional type ceiling with steel furrings

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

Table 1: Specifications of non-resistant ceiling and earthquake-resistant ceiling used in theexperiment
Item
Horizontal design load
Area mass
Clearance
Hanger lengthInterval of hangers
Hanging bolt
HangerSingle ceiling joist
Double ceiling joist
Ceiling joist receiver
Clip
Brace
Finishing material

Specification
Earthquake-resistant ceiling
1.1 [G]
13.8 [kg/m2]
60 [mm]
1,500 [mm]1,147 × 1,000 [mm]860 × 1,000 [mm]W3/8 hanging bolt
Earthquake-resistantFree hanger
free hanger
JIS19 type @364 [mm]JIS19 type @303 [mm]JIS19 type @1,820 [mm]JIS19 type @910 [mm]JIS19 type @1,000 [mm]JIS19 type @1,000 [mm]Earthquake-resistant clip
JIS19 one-touch type clip
Wind pressure resistant clip
None
Establishment
Plaster board 9.5 [mm]+rockwool absorber 9 [mm]Non-resistant ceilingNone
13.1 [kg/m2]
None

Roof

CeilingGymnasium
Figure 3: Locations of roof and ceiling in a gymnasium

Ceiling joist
receiverNail opens

Clip

Ceiling joist(a) Clip used in non-resistant ceiling(b) Clip used in earthquake-resistant ceiling

Figure 4: Clips used in the ceilings

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

3

NUMERICAL MODELS AND CONDITIONS

Two types of partial ceiling models (non-resistant ceiling and earthquake-resistant ceiling)
were prepared (Figure 5). The partial ceiling model is 1/9th the size of the ceiling used in theexperiment conducted by E-Defense, and the dimensions are 10 m  6.2 m. Figure 6 is a
simplified drawing showing an outline of the ceiling model. In the analysis, the clearance of the
non-resistant ceiling was set to 1 mm, and the clearance of the earthquake-resistant ceiling was
set to 60 mm as in the experiment. Because the ASI-Gauss code was used for the analysis, all
the ceilings and walls were modeled using linear Timoshenko beam elements. The total numberof elements and the total number of nodes for the non-resistant ceiling are 4,272 and 3,465,
respectively, and those for the earthquake-resistant ceiling are 7,404 and 6,610, respectively.
The detachment conditions shown in Table 2 were introduced to the hangers, clips, screws,
and ceiling joist joints; if the conditions were satisfied, the elements were considered to be

UD direction
UD direction
Ridge direction

Span direction

Span direction(a) Non-resistant ceiling(b) Earthquake-resistant ceiling
Figure 5: Numerical models of suspended ceilings

Hanging bolt
Ceiling joist receiver
Ceiling joist
Plaster board
Clip

25 [mm]Screw
Ceiling joist joint
25 [mm]2 [mm]
Figure 6: Outline of suspended ceiling model5

Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

fractured according to the flow of the numerical code6,7,8. A loading condition was set for thedetachment condition of the hangers; they were detached when a tensile force of 2.8 kN acted in
the axial direction of the hanger element. Different detachment conditions were set for those clips
used in the non-resistant ceiling and the earthquake-resistant ceiling. For the non-resistant ceiling,
three types of detachment conditions for the clips were set as shown in the table. For example, afront cover single clip was detached when a tensile force in the axial direction of the element
exceeds 0.35 kN. For the earthquake-resistant ceiling, two types of detachment conditions for theclips were set. For example, an earthquake-resistant clip was detached when a tensile force inthe axial direction of the element exceeds 2.50 kN. For the hangers and screws, the same
conditions are set for the non-resistant and earthquake-resistant ceilings. To prevent the
detachment of ceiling joist joints caused by instantaneous impact, the axial strain, generated
under a static tensile axial force of 0.29 kN, was set as a detachment condition in addition to theloading condition. The ceiling joist joints were detached when two conditions shown in the table
are satisfied.
The K-NET Sendai wave 200% (Figure 7) was applied to all nodes at the upper end of thehanger bolt. The time increment of the analysis was 0.001 s, and the time duration of the analysis
was 75 s.
Table 2: Detachment conditions for the joint components
Non-resistant ceiling

Earthquake-resistant ceiling

5

Tensile axial force≧2.80 kN

Hanger9

Tensile axial force≧0.40 kN and axial displacement≧3 mm
or

Screw
10

Shear force≧0.30 kN and shear displacement≧18 mm
Single(front cover)：Earthquake-resistant clip：

Clip

5

tensile axial force≧0.35 kN

tensile axial force≧2.50 kN

Single(back cover)：Wind pressure resistant clip ：5tensile axial force≧0.70 kN

tensile axial force≧2.0 kN

Double：5tensile axial force≧0.80 kN

Tensile axial force≧0.29 kN and axial strain≧4.93

Ceiling joist joint

10

2000

2000

Acceleration [gal]

加速度[gal]1000

加速度[gal]Acceleration [gal]1,506 gal

0

-1000

-2000

-844 gal
0

20

40

1000

0

-1000

-2000

60

0

20

40

時間[s]
Time [s]時間[s]Time [s](a) Ridge direction(b) Span direction

Figure 7: Input wave (K-NET Sendai wave 200%) (continued)

660

Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

加速度[gal]Acceleration [gal]

2000

1000

0

-394 gal
-1000

-2000

0

20

40

60

時間[s]
Time [s](c) UD direction
Figure 7: Input wave (K-NET Sendai wave 200%)
4

MOTION ANALYSIS OF GYMNASIUM CEILING UNDER SEISMIC EXCITATION

Figure 8 shows the snapshots of the non-resistant and earthquake-resistant ceilings at 25 s
and 70 s. At the first peak of the K-NET Sendai wave, numerous clips and ceiling joist joints
became detached and the ceilings started falling in the case of the non-resistant ceiling. And at
the second peak of the K-NET Sendai wave, the ceilings fell in a wide range. Meanwhile, theearthquake-resistant ceiling did not fall at all. Next, Figure 9 shows the locations of the detachedNon-resistant ceiling

Earthquake-resistant ceiling

UD direction
Ridge direction
Span direction(a) 25 s(b) 70 s
Figure 8: Collapse sequence of ceilings

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobeclip elements at 25 s and 70 s. In the non-resistant ceiling, both single clips and double clips aredetached in large quantities at the peak of the K-NET Sendai wave. Further, by comparing thelocation of the detached clip elements and the collapsed area of the non-resistant ceiling, asshown in Figure 10, we can confirm that the ceilings have fallen at the location where numerous
clips have detached. Figure 11 shows the response acceleration at the evaluation points shownin the figure. The response accelerations of the earthquake-resistant ceiling are suppressed in all
three directions owing to the earthquake resistance measures. We can assume that the nonresistant ceiling shakes greatly and collides with the wall such that the impact forces are
frequently delivered to the clips, and eventually cause the collapse of the ceilings. Meanwhile, thedetachment of clips did not occur in the earthquake-resistant ceiling, as shown in Figure 9. Hence,the earthquake-resistant ceiling did not fall. Further, the earthquake-resistant ceiling nevercollided with the wall because of the clearance and braces.

Span direction

Single Clip (front cover)Single Clip (back cover)

Ridge direction

Double Clip(a) Non-resistant ceiling (25s)(b) Non-resistant ceiling (70s)(c) Earthquake-resistant ceiling (70s)
Figure 9: Location of detached clip elements

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

Collapsed area(a) Non-resistant ceiling (70s)(a) Non-resistant ceiling (25s)

80

20

40

10

Acceleration [gal]Acceleration [gal]Figure 10: Collapsed area of non-resistant ceilings

0

-40

-80

0

20

40

0

-10

-20

60

0

20

Time [s](a) Ridge direction

60

Time [s](b) Span direction

200

Acceleration [gal]40Non-resistant ceilings
Earthquake-resistant ceilings

1000

Evaluation point
Non-resistant ceiling
-100

-200

0

20

40

60

Time [s]Evaluation point
Earthquake-resistant ceiling(c) UD direction

Figure 11: Response acceleration

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Kotoku Maeda, Takuzo Yamashita and Daigoro Isobe

5

CONCLUSIONSIn this study, two types of partial ceiling models (non-resistant ceiling and earthquake-resistantceiling) were prepared. Some analyses were performed using the ASI-Gauss code and by
applying a seismic wave, observed during the 2011 Great East Japan Earthquake, to the ceilingmodels.
It was observed from the numerical results that the non-resistant ceilings swayed greatly andcollided with the walls. The metal fittings detached occasionally during the impact. The ceilings
collapsed at the parts where numerous metal fittings detached. Meanwhile, none of the metal
fittings detached and the ceilings were safely installed in the case of the earthquake-resistantceilings. The earthquake-resistant ceilings never collided with the walls, owing to two primaryreasons: suppression of motion by the additional braces and the large clearance between theceiling and wall.
By comparing the numerical results of the non-resistant ceiling and earthquake-resistantceiling under a seismic excitation, the effects of the earthquake-resistant measures were
noticeably observed. However, we will continue to obtain safe but more efficient earthquake
resistance measures, as the current earthquake countermeasures exhibit problems such as highcosts and long construction periods.
REFERENCES[1]

National Institute for Land and Infrastructure Management: Report on Field Surveys andSubsequent Investigations of Building Damage Following the 2011 Off the Pacific Coast of
Tohoku Earthquake, 2012. 3 (in Japanese).

[2]

National Institute for Land and Infrastructure Management: Decree on Revision of BuildingStandards Law, No.217, 2013 (in Japanese).

[3]

National Institute for Land and Infrastructure Management: On Specific Ceiling and Its
Structurally Safe Measures, Notice by NILIM, No. 771, 2013 (in Japanese).

[4]

National Institute for Land and Infrastructure Management: On Technical Standards of Ceiling
Collapse Countermeasures in Buildings, 2013. 9 (in Japanese).

[5]T. Sasaki et al.: Collapse Mechanism of Wide-area Suspended Ceiling System Based on EDefense Full-scale Shake Table Experiments, Shake Table Experiments on Non-seismic
Suspended Ceiling and Seismically Designed Suspended Ceiling, 2015. 2 (in Japanese).

[6]

K.M. Lynn and D. Isobe: Finite Element Code for Impact Collapse Problems of Framed
Structures, International Journal for Numerical Methods in Engineering, Vol.69, No.12, pp. 25382563, 2007.

[7] D. Isobe: Progressive Collapse Analysis of Structures: Numerical Codes and Applications,Elsevier, eBook ISBN: 9780128130421, Paperback ISBN: 9780128129753, 2017.
[8] D. Isobe, T. Fujiwara, T. Yamashita, H. Tagawa and T. Sasaki: Collapse Simulation of Wide-Area
Suspended Ceiling System Using Finite Element Method, Journal of Structural and Construction
Engineering, AIJ, Vol. 82, No. 741, pp.1727-1736, 2017 (in Japanese).
[9]

H. Chinzei et al.: Pull Out Experiment and Collapse Mechanism of Tapping Screw Connection
Study on Mechanical Characteristic of Tapping Screw: Connection in Non-structural Components
Part 1, Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, B-1,
pp. 891-892, 2015. 9 (in Japanese).

[10] T. Sugiyama et al.: Shear Tests of Screwed Joint between Ceiling Joist and Plaster Board ofConventional Type Ceiling Part 1: Test Plan and Results of Element Tests, Summaries ofTechnical Papers of Annual Meeting, Architectural Institute of Japan, B-1, pp. 871-872, 2010. 7(in Japanese).

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