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CEILING SYSTEMS
ShortSpan Brochure1
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ShortSpan Brochure1
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Armstrong ShortSpan Drywall Grid System was
introduced to the North American commercial
building market early in 2005. Many of its
properties are similar to other framing systems
commonly used today, but the designs and
the installation system depart somewhat from
current industry practice.
Use this data to qualify ShortSpan as acceptable
for use on your project or with your building
code. If you have questions after reviewing this
information, contact Armstrong at 877 276 7876.
This document will provide the following
information:
• Physical Performance Summary
• Mechanical Performance Summary
• Section Properties
• Seismic performance Summary
To assist you in the use of this brochure,
please obtain a copy of the ShortSpan
DGS Technical Guide (CS-3590) from your
Armstrong representative.
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The information contained in this technical paper will provide the user of
the Armstrong ShortSpan DGS (drywall grid system) with a summary of
the performance of the product. The summary contains information on
the physical, mechanical and seismic performance of the system.
The Armstrong ShortSpan DGS consists of the following; 8′, 10′, 12′
and 14′ T-bar; 12′ locking angle mold and 12′ knurled angle molding.
The ShortSpan system is designed for use in drywall ceiling framing
where the spans are less than 14 feet. The individual ShortSpan Tees
are not designed to be used independent of the Locking Angle molding
or optional Knurled Angle molding as instructed in our technical guide.
The ShortSpan DGS is to be used with drywall, up to 5/8″, weighing
up to 2.50 lbs/ft 2. The attached charts reflect the ShortSpan Systems
capacities. Although the Armstrong ShortSpan DGS performance is
comparable to current construction practices for framing short spans,
the building codes do not clearly provide provisions for the use of a
ShortSpan grid framing system for installation of a drywall ceiling.
Therefore, as the manufacturer we are providing additional data
including a summary of the mechanical test data as prescribed by
the recognized ASTM test methods used in the industry today to
document the performance of these systems and to give a
comparison to traditional framing components.
Installation Standards
ASTM C635-04, Standard Specification for the Manufacture,
Performance and Testing of Metal Suspension Systems for
Acoustical Tile and Lay-In Panel Testing
ASTM C645-04 Standard Specification for Nonstructural Steel
Framing Members
ASTM E580-02 Standard Practice for Application of Ceiling
Suspension Systems for Acoustical Tile and Lay-In Panels in
Areas Requiring Moderate Seismic Restraint
ASTM E8-04 Standard Test Method for Tension Testing for
Metallic Materials
ASTM A-653 Standard Specification for Steel Sheet, ZincCoated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed)
by the Hot-Dip Process
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Physical Performance
Summary
Tees installed 16″ or 24″ on center with 5/8″ drywall
Up to 6′ 0″ span
No vertical support required
6′ 1″ to 12′ 0″ span
Mid-span vertical support required
12′ 1″ to 14′ 0″ span
Two vertical supports required at 1/3 points (max. 14′ span)
Tees installed 16″ on center only with 1/2″ drywall
Up to 7′ 0″ span
No vertical support required
7′ 1″ to 14′ 0″ span
Mid-span vertical support required
Maximum Load in Lbs./SF (L/240 per ASTM C 645)
Item
Item
O.C.
Number Length Spacing
4′
5′
6′
7′
8′
10′ Span 12′ Span 14′ Span
Span
Span
Span
Span
Span
Lbs./SF Lbs./SF Lbs./SF
Lbs./SF Lbs./SF Lbs./SF Lbs./SF Lbs./SF
S7708
8′
16″
18.38
18.38**
S7708
8′
24″
12.25
12.25**
S7710
10′
16″
9.54
9.54**
S7710
10′
24″
6.36
6.36**
S7712
12′
16″
4.87
4.87**
S7712
12′
24″
3.25
3.25**
S7714
14′
16″
2.80
2.80**
S7714
14′
16″
24.70**
9.53***
S7714
14′
24″
16.50**
6.36***
**Requires mid-span vertical support
*** Requires two vertical supports at 1/3 points
NOTE: 5/8″ drywall weighs 2.4 lbs./SF (tees installed 16″ or 24″ on center)
1/2″ drywall weighs 2.0 lbs/SF (tees installed 16″ on center only)
Load Test per ASTM C 635-04
Part Number
S7708, S7710, S7712, S7714
LAM12 / KAM 12
Mechanical
Performance
Summary
Description
Length
8′, 10′ 12′ 14′ ShortSpan (0.018″)
Drywall Tee
12′ ShortSpan (0.018″) Wall
Molding
Tested 48″, 60″ and 72″ on
Center
24″ on Center
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The following tables contain a summary of test results:
Load Test Average per ASTM C 635
Part Number
Load at L/360 (LBS/LF)
Load at Failure (LBS/LF)
Total Load at Failure
(LBS)
S7708, S7710, S7712, 16.33
S7714 48″ span
(L/240 = 23.2)
62.33
249.32
S7708, S7710, S7712, 8.48
S7714 60″ span
(L/240 = 12.11)
39.66
198.3
S7708, S7710, S7712, 4.33
S7714 72″ span
(L/240 = 6.18)
23.49
140.94
ShortSpan Wall Molding Load Test Average
Part Number
Test Condition
Supported Load (LBS/LF)
LAM 12/ KAM 12
Average of 4 tests
100
Section Properties
Tensile Test Per ASTM E 8-04
Property
Sample
Value
Average Base Metal Thickness
All
0.0186″
Average Yield Strength by Offset Method
All
47,792 psi
Average Yield Point by Graphical Method
All
0.34% in./in.
Young's Modulus (Modulus of Elasticity)
Maximum Average
34, 339, 100 psi 32, 118,
980 psi
Tensile Strength
Average
61,321
Ultimate Load
Average
578.6 lbs
Elongation
Average
35.6%
Reduction of Area
Average
32.0%
Nominal Test Section Dimension
(Thickness x Width Prior to Testing)
Average
0.0188″ x 0.502″
The complete report from Architectural Testing and Section Properties
(Moment of Inertia, Section of Modulus and Yield Strength) are available
upon request from your Armstrong Representative.
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Additionally, full-scale seismic testing was performed utilizing the
University at Buffalo Earthquake Simulation (Shake Table) apparatus.
The full-scale dynamic testing was performed according to a modified
ICC Acceptance Criteria for Seismic Qualification Testing of
Nonstructural Components, AC 156. This criterion was modified to
make it specific for the testing of grid system types, i.e. ShortSpan.
The complete test protocol and test program is contained in Report
No.UBCSEE/SEESL-2005-01, dated March 1, 2005.
Seismic Performance
Summary
Armstrong conducted tests on the ShortSpan system using the seismic
simulation based on the mapped spectral accelerations at short periods
of SS up to 1.75G (from the International Building Code, 2003). Spectra
were generated for horizontal and vertical earthquake shaking.
Three separate configurations were tested. The first consisted of two
16 ft. (4.88 m) long and 5 ft. (1.52 m) high walls running in the northsouth direction constructed of 3-5/8 in. (92 mm) 20 gauge steel studs
spaced at 16 in. (406 mm) on center; a distance of 14 ft. (4.27 m)
was maintained between the two walls. A single layer of 5/8 in.
(16 mm) thick drywall was attached to the exterior surfaces of the
walls using 1-1/4 in. (32 mm) #6 bugle-head drywall screws.
A locking angle molding was screwed directly to the steel studs with
#7 x 7/16 in. (11 mm) sheet metal screws; the molding had perforated
tabs to lock the drywall Tees into the proper spacing and alignment.
Drywall Tees were spaced at 2 ft. (0.61 m) on center. All drywall Tees
ends were screwed to the locking angle molding with #7 x 7/16 in.
(11mm) sheet metal screws. Each Tee had two soft annealed
galvanized number 12 gage steel suspension wire located 6 ft.
(1.83 m) and 6-1/3 ft. (1.93 m) from the west and east wall of the test
frame, respectively.
Stabilizer bars were installed to maintain the 2 ft. (0.61 m) spacing
between the drywall Tees. Type X 5/8 in. (16mm) thick drywall panels
were screwed to the Tees using 1-1/4 in. (32 mm) #6 bugle-head
drywall screws spaced at 12 in. (305 mm) on center. The drywall was
not screwed to the locking angle molding or to the drywall Tees within
4 in. (102 mm) of any wall.
For the second configuration, the screws anchoring the Tees to the
locking angle molding were removed and the ceiling was tested again.
The third configuration consisted of two simulated corridors both
running in the north-south direction of the test frame. One corridor
consisted of two 16 ft. (4.88 m) long and 5 ft. (1.52 m) high walls
running in the north-south direction constructed from 3-5/8 in.
(92 mm) 20 gauge steel studs spaced at 16 in. (406 mm) on center.
The walls were located 6 ft. (1.83 m) apart from each other. A single
layer of 5/8 in. (16 mm) drywall was attached to the exterior surfaces
of the corridor by using 1-1/4 in. (32 mm) #6 bugle-head drywall
screws. The locking angle was screwed directly to the steel studs with
#7 x 7/16 in. (11 mm) sheet metal screws, and had perforated tabs to
lock the drywall Tees into the proper spacing and alignment.
The drywall Tees were spaced at 2 ft. (0.61 m) on center installed
between the two walls of the west corridor. The drywall Tees were
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screwed to the locking angle molding. No suspension wires were
used in the system. Type X 5/8 in. (16 mm) drywall panels were
screwed to the Tees using 1-1/4 in. (32 mm) #6 bugle-head drywall
screws spaced at 12 in. (305 mm) on center.
The second corridor consisted of two 16 ft. (4.88 m) long and 5 ft.
(1.52 m) high walls running in the north-south direction constructed
from 2-1/2 in. (64 mm) 25 gauge steel studs spaced at 16 in. on center.
The two walls were located 6 ft. (1.83 m) apart from each other. A single
layer of 5/8 in. (16 mm) drywall was attached to the interior surfaces of
the corridor by using 1-1/4 in. (32 mm) #6 bugle-head drywall screws.
The locking angle molding was screwed to the wall by anchoring
through the 5/8 in. (16 mm) thick drywall using 1-1/4 in. (32 mm) #6
bugle-head drywall screws.
The drywall Tees were spaced at 2 ft. (0.61 m) on center. The drywall
Tees were not screwed to the locking angle molding and no suspension
wires were used. Type X 5/8 in. (16 mm) drywall panels were screwed
to the Tees using 1-1/4 in. (32 mm) #6 bugle-head drywall screws
spaced at 12 in. (305 mm) on center.
All corridor walls were laterally braced to the structure above. Support
walls were tied directly to the structure.
For the ShortSpan grid system, two performance limit states were
defined as: 1.) no damage to the suspension system and 2.) no
damage to or loss of any drywall panel or component. Qualification
levels were determined as the level of shaking at which the limit state
was not reached. The results for each test configuration was that
there was “no damage to the drywall or any suspension system
component.” For these evaluations testing was done to a maximum
shaking intensity of 1.75g.
Seismic Conclusion
Testing
Series
Ceiling
system ID
Qualification level (g)
System
description
Limit state 1
Limit state 2
8a
Test of a ShortSpan (14 ft.) drywall grid
system
1.75
1.75
L9
8b
ShortSpan (14 ft.) drywall grid system of
8a retested after removing the screws
anchoring the Tees to the locking angle
molding.
1.75
1.75
M9
9
Tests of two ShortSpan (6 ft.) drywall grid
systems.
1.75
1.75
K8
For the official seismic test report, please contact your Armstrong
Representative.
CEILING SYSTEMS
1 877 ARMSTRONG (276 7876)
armstrong.com/ceilings
CS-3681-605
© 2005 AWI Licensing Co.
Printed in the United States of America