Standard Practice for Determining the Thickness of Glass in Airport Traffic Control Tower Cabs

SCOPE
1.1 This practice covers the determination of the thickness of glass installed in airport traffic control towers (ATCT) to resist a specified design loading with a selected probability of breakage less than or equal to either 1 lite per 1000 or 4 lites per 1000 at the first occurrence of the design wind loading.
1.2 The procedures apply to common outward sloping cab glass designs for which the specified loads do not exceed 10 kPa (210 psf).
1.3 The procedures assume control tower cab glass has an aspect ratio no greater than 2.
1.4 The procedures assume control tower cab glass has an area no less than 1.86 square metres (20 square feet).
1.5 The procedures apply only to annealed monolithic, annealed laminated, or annealed insulating glass having a rectangular or trapezoidal shape.
1.6 The use of the procedures assumes the following:
1.6.1 Annealed monolithic and annealed laminated glass installed in ATCTs shall have continuous lateral support along two parallel edges, along any three edges, or along all four edges;
1.6.2 Insulating glass shall have continuous lateral support along all four edges; and
1.6.3 Supported glass edges are simply supported and free to slip in plane.
1.7 The procedures do not apply to any form of wired, patterned, etched, sandblasted, or glass types with surface treatments that reduce the glass strength.
1.8 The procedures do not apply to any form of heat treated glass, chemically strengthened glass, or any type of glass with surface treatments intended to increase the glass strength.
1.9 The procedures address the determination of thickness and construction type to resist a specified design wind load at a selected probability of breakage. The final glass thickness and construction determined also depends upon a variety of other factors (see ).
1.10 These procedures do not address blast loading on glass.
1.11 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2461 – 05 (Reapproved 2011)
Standard Practice for
Determining the Thickness of Glass in Airport Traffic
Control Tower Cabs
This standard is issued under the fixed designation E2461; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.10 Theseproceduresdonotaddressblastloadingonglass.
1.11 The values stated in SI units are to be regarded as
1.1 This practice covers the determination of the thickness
standard. The values given in parentheses are mathematical
of glass installed in airport traffic control towers (ATCT) to
conversions to inch-pound units that are provided for informa-
resist a specified design loading with a selected probability of
tion only and are not considered standard.
breakage less than or equal to either 1 lite per 1000 or 4 lites
1.12 This standard does not purport to address all of the
per 1000 at the first occurrence of the design wind loading.
safety concerns, if any, associated with its use. It is the
1.2 The procedures apply to common outward sloping cab
responsibility of the user of this standard to establish appro-
glass designs for which the specified loads do not exceed 10
priate safety and health practices and to determine the
kPa (210 psf).
applicability of regulatory limitations prior to use.
1.3 The procedures assume control tower cab glass has an
aspect ratio no greater than 2.
2. Referenced Documents
1.4 The procedures assume control tower cab glass has an
2.1 ASTM Standards:
area no less than 1.86 square metres (20 square feet).
C1036 Specification for Flat Glass
1.5 The procedures apply only to annealed monolithic,
E631 Terminology of Building Constructions
annealed laminated, or annealed insulating glass having a
E1300 Practice for Determining Load Resistance of Glass
rectangular or trapezoidal shape.
in Buildings
1.6 The use of the procedures assumes the following:
2.2 American Society of Civil Engineers Standard:
1.6.1 Annealed monolithic and annealed laminated glass
ASCE 7 Minimum Design Loads for Buildings and Other
installed in ATCTs shall have continuous lateral support along
Structures
two parallel edges, along any three edges, or along all four
edges;
3. Terminology
1.6.2 Insulating glass shall have continuous lateral support
3.1 Definitions:
along all four edges; and
3.1.1 Refer to Terminology E631 for additional terms used
1.6.3 Supported glass edges are simply supported and free
in these procedures.
to slip in plane.
3.2 Definitions of Terms Specific to This Standard:
1.7 The procedures do not apply to any form of wired,
3.2.1 annealed (AN) glass, n—a flat, monolithic, glass lite
patterned, etched, sandblasted, or glass types with surface
of uniform thickness; it is formed by a process whereby the
treatments that reduce the glass strength.
magnitudes of the residual stresses are nearly zero.
1.8 The procedures do not apply to any form of heat treated
3.2.2 aspect ratio (AR), n—the ratio of the long dimension
glass, chemically strengthened glass, or any type of glass with
to the short dimension for rectangular glass or the ratio of the
surface treatments intended to increase the glass strength.
long dimension to the short dimension of the rectangle that
1.9 The procedures address the determination of thickness
completely encloses trapezoidal glass. In these procedures,AR
and construction type to resist a specified design wind load at
is always equal to or greater than 1.0.
a selected probability of breakage. The final glass thickness
and construction determined also depends upon a variety of
NOTE 1—The rectangle that completely encloses the trapezoid has two
sides parallel to the horizontal edges of the trapezoid and the other two
other factors (see 5.3).
1 2
This practice is under the jurisdiction of ASTM Committee E06 on Perfor- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mance of Buildings and is the direct responsibility of Subcommittee E06.51 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Performance of Windows, Doors, Skylights and Curtain Walls. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2011. Published November 2011. Originally the ASTM website.
approved in 2005. Last previous edition in 2005 as E2421 – 05 (2011). DOI: Available from American Society of Civil Engineers (ASCE), 1801 Alexander
10.1520/E2461-05R11. Bell Dr., Reston, VA 20191, http://www.asce.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2461 – 05 (2011)
sides perpendicular to the horizontal edges of the trapezoid. All dimen- TABLE 2 Thickness Designations, Minimum Glass Thickness,
and Unit Self-Weight
sions shall be measured from edge to edge of glass.
Nominal thickness or Minimum thickness, mm Glass weight
3.2.3 equivalent rectangular area (ERA), n—the product of
designation. mm (in.) (in.) Pa (psf)
the longest horizontal glass dimension and the length of the
2.7 (lami) 2.59 (0.102) 67.0 (1.40)
edge perpendicular to the horizontal dimension in the plane of
3.0 ( ⁄8) 2.92 (0.115) 74.2 (1.55)
the glass.All dimensions shall be measured from edge to edge
4.0 ( ⁄32) 3.78 (0.149) 99.1 (2.07)
5.0 ( ⁄16) 4.57 (0.180) 124 (2.59)
of glass.
6.0 ( ⁄4) 5.56 (0.219) 149 (3.11)
3.2.4 designated thickness for laminated glass (LG), n—the
8.0 ( ⁄16) 7.42 (0.292) 199 (4.15)
designated thickness for LG as Table 1 specifies.
10.0 ( ⁄8) 9.02 (0.355) 248 (5.18)
12.0 ( ⁄2) 11.91 (0.469) 298 (6.22)
3.2.5 designated thickness for monolithic glass, n—the
16.0 ( ⁄8) 15.09 (0.595) 397 (8.29)
designated or nominal thickness commonly used in specifying
19.0 ( ⁄4) 18.26 (0.719) 472 (9.85)
a particular glass product, based on the minimum thicknesses 22.0 ( ⁄8) 21.44 (0.844) 546 (11.4)
25.0 (1)* 24.4 (0.969) 622 (13.0)
presented in Table 2 and Specification C1036.
A
32 (1 – ⁄4) 27.38 (1.22) 795 (16.6)
3.2.6 glass breakage, n—the fracture of any lite or ply in A
38 (1 – ⁄2) 31.6 (1.47) 943 (19.7)
monolithic, laminated, or insulating glass resulting from stress
A
Not a glazing industry standard thickness designation.
that an applied uniform lateral load induces.
3.2.7 insulating glass (IG) unit, n—consists of any combi-
nationoftwoglasslites,asdefinedherein,thatencloseasealed
3.2.10.2 specified design load, n—the magnitude in kPa
space filled with air or other gas.
(psf), type (for example, wind or self-weight) and duration of
3.2.8 laminated glass (LG), n—a flat-lite of uniform thick-
the load. The wind load has a duration of approximately 3
nessthatisfabricatedbybondingtwoormoremonolithicglass
seconds. Glass self-weight (Table 2) has a long duration,
litesorpliesofequalthickness,asdefinedherein,togetherwith
typically equal to the in-service life of the window glass lite.
polyvinyl butyral (PVB) interlayer(s).
Earth facing cab glass is only subjected to wind load and its
3.2.9 lateral, adj—perpendicular to the glass surface.
self-weight.
3.2.10 load, n—a uniformly distributed lateral pressure.
3.2.10.1 design load, n—the magnitude of the 3-second
3.2.10.3 long duration load, n—any load lasting approxi-
duration load used to design glass for ATCT cabs. Equations
mately 30 days or longer.
used herein for computing magnitudes for design loads adjust
3.2.10.4 short duration load, n—any load lasting approxi-
glass self weight to a magnitude consistent with a 3-second
mately 3 seconds, such as, wind load.
duration.
TABLE 1 Thickness Designations for Laminated Glass
Laminated glass Laminated glass construction Laminated glass thickness
designation, t, nominal thickness, mm (in.) designation for use in these
mm (in.) [glass/PVB/glass] procedures mm (in.)
2.7/0.76/2.7 {(lami)/0.030/(lami)}
1 1
6( ⁄4) 6( ⁄4)
1 1
3/0.76/3 {( ⁄8)/0.030/( ⁄8)}
1 1
3/1.52/3 {( ⁄8)/0.060/( ⁄8)}
5 5 5 5
8( ⁄16) 4/0.76/4 {( ⁄32)/0.030/( ⁄32)} 8 ( ⁄16)
3 3 3 3
10 ( ⁄8) 5/0.76/5 {( ⁄16)/0.030/( ⁄16)} 10 ( ⁄8)
7 3 3
11 ( ⁄16) 5/1.52/5 {( ⁄16)/0.060/( ⁄16)}
1 1 1 1
12 ( ⁄2) 6/0.76/6 {( ⁄4)/0.030/( ⁄4)} 12 ( ⁄2)
9 1 1
13 ( ⁄16) 6/1.52/6 {( ⁄4)/0.060/( ⁄4)}
5 5
8/0.76/8 {( ⁄16)/0.030/( ⁄16)}
5 5
16 ( ⁄8) 5 5 16 ( ⁄8)
8/1.52/8 {( ⁄16)/0.060/( ⁄16)}
5 5
8/2.28/8 {( ⁄16)/0.090/( ⁄16)}
3 3
10/0.76/10 {( ⁄8)/0.030/( ⁄8)}
3 3
19 ( ⁄4) 3 3 19 ( ⁄4)
10/1.52/10 {( ⁄8)/0.060/( ⁄8)}
3 3
10/2.28/10 {( ⁄8)/0.090/( ⁄8)}
1 1
12/1.52/12 {( ⁄2)/0.060/( ⁄2)}
25 (1) 25 (1)
1 1
12/2.28/12 {( ⁄2)/0.090/( ⁄2)}
5 5
16/1.52/16 {( ⁄8)/0.060/( ⁄8)}
1 1
32 (1 ⁄4) 32 (1 ⁄4)
5 5
16/2.28/16 {( ⁄8)/0.090/( ⁄8)}
3 3
19/1.52/19 {( ⁄4)/0.060/( ⁄4)}
1 1
38 (1 ⁄2) 38 (1 ⁄2)
3 3
19/2.28/19 {( ⁄4)/0.090/( ⁄4)}
E2461 – 05 (2011)
3.2.11 minimum thickness of monolithic glass, n—the mini- 6. Procedure
mum allowable thickness associated with a nominal or desig-
6.1 Select a probability of breakage, glass type or construc-
nated glass thickness as given in Table 2 and Specification
tion, and glass thickness(es).
C1036.
6.2 Compute the design load for monolithic or single
3.2.12 probability of breakage (P ), n—the theoretical frac-
b
laminated glass according to:
tion of glass lites or plies that would break at the first
L 5 L 1 2L cosu (1)
D W G
occurrence of the resistance load, typically expressed in lites
per thousand.
where:
L = denotes the design load,
D
4. Summary of Practice
L = denotes the wind load,
W
L = denotes the weight of the glass, and
G
4.1 The use of these procedures requires a specified design
u = denotes the acute angle the glass makes with the
load that shall consist of the wind load and the factored lateral
horizontal. For monolithic or single laminated glaz-
component of glass weight. The total design load shall not
ing, the user shall obtain L from Table 2 for the
G
exceed 10 kPa (210 psf).
nominal glass thickness. For insulating glass, L
G
4.2 The procedures specified herein facilitate determination
shall consist of the weights of both glass lites as
of the thickness of an annealed window glass construction
determined from Table 2.
required to resist the specified design loading for the selected
6.3 Monolithic Single Glazing Continuously Supported
probability of breakage.
Along all Four Edges:
4.3 ThisstandardprocedureusesmethodsinPracticeE1300
6.3.1 Determine the ERA.
to determine the approximate lateral deflection of the geomet-
6.3.2 Determine the AR.
riccenterofthewindowglassconstruction.AnnexA2provides
6.3.3 Determine the required glass thickness from Fig.A1.1
deflection charts for laminated glass thicknesses larger than
(P = 0.001) or Fig.A1.2 P = 0.004) for the design load, ERA,
those contained in Practice E1300. B B
and AR.
6.3.4 Determine the approximate maximum center of glass
5. Significance and Use
deflection using procedures from Practice E1300.
5.1 This standard procedure facilitates determination of the
6.4 Single Laminated Glazing Continuously Supported
thickness of a glass construction required to resist a specified
Along all Four Edges:
design load with a selected probability of breakage.
6.4.1 Determine the ERA.
5.2 This standard procedure addresses the following glass
6.4.2 Determine the AR.
constructions: annealed monolithic, annealed laminated, and
6.4.3 Determine the required glass thickness from Fig.A1.3
insulating glass fabricated with annealed monolithic or an-
(P =0.001)orFig.A1.4(P =0.004)forthedesignload,ERA,
B B
nealed laminated glass, or both.
and AR.
5.3 Use of these procedures assume:
6.4.4 Determine the approximate maximum center of glass
5.3.1 The glass is free of edge damage and is properly
deflection using procedures from Practice E1300.
glazed,
6.5 Monolithic Single Glazing Simply Supported Continu-
5.3.2 The glass has not been subjected to abuse,
ously Along Two Opposite Sides or any Three Sides:
5.3.3 The surface condition of the glass is typical of glass
6.5.1 Determine the Unsupported Glass Length.
that has been in service for several years, and is significantly
6.5.2 Determine the required glass thickness from Fig.A1.5
weaker than freshly manufactured glass due to minor abrasions
(P =0.001)orFig.A1.6(P =0.004)forthedesignload,ERA,
B B
on exposed surfaces,
and AR.
5.3.4 The glass edge support system is sufficiently stiff to
6.5.3 Determine the approximate maximum center of glass
limit the lateral deflections of the supported glass edges to less
deflection using procedures from Practice E1300.
than 1/175 of their lengths. The specified design load shall be
6.6 Single Laminated Glazing Simply Supported Continu-
used for this calculation, and
ously Along Two Opposite Sides or any Three Sides:
5.3.5 The center of glass deflection shall not result in loss of
6.6.1 Determine the unsupported glass length.
edge support. Typically maintaining center of glass deflection
6.6.2 Determine the required glass thickness from Fig.A1.7
at or below the magnitude of three times the nominal glass
(P =0.001)orFig.A1.8(P =0.004)forthedesignload,ERA,
thickness assures that no loss of edge support will occur. B B
and AR.
5.4 Many other factors affect the selection of glass type and
6.6.3 Determine the approximate maximum center of glass
thickness. These factors include but are not limited to: thermal
deflection using procedures from Practice E1300.
stresses, the effects of windborne debris, excessive deflections,
6.7 Insulating Glass (IG) with Monolithic Glass Lites of
behavior of glass fragments after breakage, seismic effects,
Equal (Symmetric) Glass Type and Thickness.
heat flow, edge bite, noise abatement, potential post-breakage
6.7.1 Compute the design load for IG as L 5 5~L 1
consequences, and so forth. In addition, considerations set
DIG W
2L cosu!/9 in which all terms are previously defined. The
forth in federal, state, and local building codes along with
G
weighoftheglass,L ,consistsoftheweightofbothglasslites.
criteria presented in safety glazing standards and site specific
G
6.7.2 Determine the ERA.
concerns may control the ultimate glass type and thickness
selection. 6.7.3 Determine the AR.
E2461 – 05 (2011)
6.7.4 Determine the required glass thickness for a single lite glass type(s) and thickness(es), weight of the glass, glass type
in the IG unit from Fig. A1.1 (P = 0.001) or Fig. A1.2 (P = factor(s), approximate lateral deflection; and
B B
0.004) for the design load, ERA, and AR. 7.1.3 A statement that the procedure followed was in
6.7.5 Determine the approximate maximum center of glass accordance with this practice or a full description of any
deflectio
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