ASTM E2431-06

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Designation:E2431–06
Standard Practice for
Determining the Resistance of Single Glazed Annealed
Architectural Flat Glass to Thermal Loadings
This standard is issued under the fixed designation E2431; 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 2. Referenced Documents
1.1 This practice covers a procedure to determine the 2.1 ASTM Documents:
resistance of annealed architectural flat glass to thermally C162 Terminology of Glass and Glass Products
induced stresses caused by exposure to sun and shadows for a E631 Terminology of Building Constructions
specified probability of breakage (P ). Proper use of this IEEE/ASTMSI-10 UseoftheInternationalSystemofUnits
b
procedure is intended to reduce the possibility of thermal (SI) (the Modernized Metric System)
breakage of annealed glass in buildings. 2.2 Other Documents:
1.2 This practice applies to vertical or sloped glazing in 2005 ASHRAE Handbook Fundamentals
buildings.
3. Terminology
1.3 This practice applies to monolithic and laminated glass
3.1 Definitions:
of rectangular shape and assumes that all glass edges are
simply supported. 3.1.1 Refer to Terminologies and for additional terms used
in this practice
1.4 This practice applies only to annealed flat soda-lime
silica glass with clean cut, seamed, flat ground, or ground and 3.2 Definitions of Terms Specific to This Standard:
3.2.1 edge bite, n—the width of the glass edge (measured
polished edges that are free from damage. The glass may be
clear or tinted as well as coated (not including coatings that perpendicular to the cut edge, in the plane of the glass) that is
protected from direct exposure to solar irradiance by the
reduce emissivity of the glass).
1.5 This practice does not apply to any form of wired, window frame edge conditions expressed in mm (in.) [See
Table 1].
patterned, etched, sandblasted, drilled, notched, or grooved
3.2.2 edge thermal stress factor (TSF ), n—the ratio of
glass or glass with surface and edge treatments, other than
edge
those described in section 1.4, that alter the glass strength. induced thermal stress to the solar load, SL, as the result of the
edge bite condition expressed in MPa/(W/m ).
1.6 This practice does not address uniform loads such as
wind and snow loads, safety requirements, fire, or impact 3.2.3 frame type, n—the manner in which the edges of the
glass are supported in the window frame [See Table 1].
resistance.
1.7 The values stated in SI units are to be regarded as the 3.2.4 glass dimensions, n—the rectangular dimensions of
the glass (not the daylight opening), with the width being the
standard. The values given in parentheses are for information
only. For conversion of quantities in various systems of smaller dimension and the length being the larger dimension
both expressed in mm.
measurements to SI units refer to IEEE/ASTM SI-10.
1.8 This standard does not purport to address all of the 3.2.5 incident solar irradiance (Insolation), (I ), n—amount
s
of solar energy per unit time per unit area normal to glass, to
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- which the glass is exposed expressed in W/m .
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee E06 on Perfor- Standards volume information, refer to the standard’s Document Summary page on
mance of Buildings and is the direct responsibility of Subcommittee E06.51 on the ASTM website.
Performance of Windows, Doors, Skylights, and Curtain Walls. Available from American Society of Heating, Refrigerating, and Air-
Current edition approved Feb. 1, 2006. Published February 2006. DOI: 10.1520/ Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA
E2431-06. 30329.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2431–06
TABLE 1 Frame Types.
Frame Type Sketch
Insulated edge -- This condition should only be used in the analysis if it can
reasonably be assumed that the heat loss from the glass to the glazing
pocket is negligible.
Conventional edge -- This condition should be used in the analysis only when
the glazing pocket is fabricated with thin walled members and the glass is
cushioned with gasket materials as shown.
High heat mass edge -- This condition should be used in the analysis when the
glazing is encapsulated in a material with a high heat mass such as concrete,
heavy metal, and so forth.
3.2.6 probability of breakage (P ), n—the number of lites 3.2.8 solar load (SL), n—the total amount of solar irradi-
b
per 1000 that would be predicted to break when exposed to the ance absorbed by the glass expressed in W/m .
specified thermal loading conditions. 3.2.9 solar load adjustment factor for interior shading
3.2.7 shadow thermal stress factor (TSF ), n—the ratio devices (SLA), n—nondimensional factor that is used to
shadow
of induced thermal stress to the solar load, SL, as the result of account for the increase in thermal stress caused by the
2 2
shadow condition expressed in MPa/(W/m ) (psi/Btu/hr·ft ). reflection of solar irradiance from an interior shading device.
E2431–06
3.2.10 solar reflectance of shading device (R ), n—decimal 5.4 The proper use of this practice is intended to reduce the
s
fraction of incident solar irradiation reflected from the device risk of thermally induced breakage of annealed window glass
used as an interior shade. in buildings.
3.2.11 solar transmittance (T ), n—the amount of solar
s
6. Procedure
irradiance transmitted by the glass expressed as a fraction that
ranges between 0.00 and 1.00.
6.1 Obtain the following information from the data supplied
3.2.12 thermal stress, n—edge tensile stress (MPa) induced
by the specifier:
in glass by solar irradiance. 6.1.1 theedgebiteconditionthatmostcloselyrepresentsthe
3.2.13 total solar absorptance (A ), n—the amount of solar
project conditions from Table 1,
s
irradiance absorbed by the glass expressed as a fraction that 6.1.2 the total solar transmittance (T ) of the specified glass,
s
ranges between 0.00 and 1.00.
6.1.3 the total solar absorptance (A ) of the specified glass.
s
3.2.14 total thermal stress factor (TSF ), n—the ratio of
tot
A 51.002T 2 R (1)
s s s
total thermal stress induced in the glass by the combination of
where:
edge conditions and shadow conditions to the solar load
R = total solar reflectance
expressed in MPa/(W/m ).
s
6.1.4 the solar reflectance of the shading device (RSD), if
4. Summary of Practice
used.
4.1 The specifying authority shall provide the glass width, 6.1.5 the incident solar irradiance (I ) for this analysis.
s
length, and nominal thickness; solar absorption of the glass 6.1.6 the specified acceptable probability of glass breakage
construction (can be obtained from manufacturer’s data); (P ) for this analysis.
b
incident solar irradiance (can be determined from 2005 6.2 Multiply the incident solar irradiance (I ) by the solar
s
ASHRAE Handbook Fundamentals or other documented absorptance (A ) to determine the solar load (SL).
S
source); the frame type and edge bite; description of exterior 6.3 Determine the edge thermal stress factor (TSF ) from
edge
shading conditions; and interior shading devices. Fig. 1, given the edge bite and edge bite condition.
4.2 The procedure described in this practice shall be used to 6.4 Determine the shadow thermal stress factor (TSF )
shadow
using the common shadow patterns shown in Fig. 2 and the
determine if the glass can resist the calculated thermal stresses
for a specified probability of breakage. factors listed in Table 2.
5. Significance and Use
TABLE 2 Shadow Thermal Stress Factors to be Used with Fig. 2.
5.1 Use of this practice assumes:
Shadow Condition Maximum TSF
shadow
5.1.1 the glass edges shall be free from damage,
kPa/(W/sq m)
5.1.2 the glass shall be properly glazed,
Linear shadow 15.3
5.1.3 the glass shall not have been subjected to abuse, and
Angular shadow 31.9
L-Shaped shadow 20.8
5.1.4 the glass edge support allows in-plane movement of
Corner shadow 23.0
the glass due to thermal expansion and contraction.
5.2 This practice does not address all factors that cause
thermally induced stresses in annealed glass. Factors that are
6.5 Determine the total thermal stress factor (TSF )by
not addressed include: transient thermal stresses, HVAC reg-
total
summing the individual thermal stress factors given in 6.3 and
isters, thermally insulating window coverings, drop ceilings
6.4.
and other heat traps, increased solar irradiance caused by
6.5.1 If the calculated total thermal stress factor exceeds
exteriorreflections,variationsinheattransfercoefficientsother
39.4 kPa/(W/m ) when the angular shadow pattern is assumed,
than those assumed for the steady state analysis described
that is, Fig. 2 b and d, then 39.4 kPa/(W/m ) shall be used for
herein, and stresses induced by thermal sources other than the
the total thermal stress factor.
sun. Factors other than those listed above may also induce
6.5.2 If the calculated total thermal stress factor exceeds
thermal stress.
32.0 kPa/(W/m ) when other shadow patterns, that is, Fig. 2 a
5.3 Many other factors shall be considered in glass selec-
and c, are assumed, then 32.0 kPa/(W/m ) shall be used for the
tion.These factors include, but are not limited to, mechanically
total thermal stress factor.
induced stresses, wind effects, windborne debris impacts,
6.6 To determine the solar load adjustment factor (SLA)
excessive deflections, seismic effects, heat flow, noise abate-
using Fig. 3, enter the vertical axis with the solar reflectance of
ment, potential post-breakage consequences, and so forth. In
the shading device (RSD) and the horizontal axis with total
addition, considerations set forth in building codes along with
solar transmittance of the glass (T ) to determine the solar load
criteria presented in safety glazing standards and site specific
S
adjustment factor (SLA) for interior shading devices. If nec-
concerns may control the ultimate glass type and thickness
essary use interpolation to estimate the solar load adjustment
selection.
factor (SLA). If no shading device is used, the solar load
adjustment factor (SLA) shall be taken to be 1.0.
Beason, W.L., and Lingnell,A.W., “AThermal Stress Evaluation Procedure
6.7 Determine the calculated thermal stress, s ,by
calculated
for Monolithic Annealed Glass,” Use of Glass in Buildings, ASTM STP 1434,V.
multiplyingthetotalthermalstressfactor(TSF )bythesolar
Block, Ed., American Society for Testing and Materials, West Conshohocken, PA, total
2003. load (SL) and by the solar load adjustment factor (SLA).
E2431–06
FIG. 1 Edge Thermal Stress Factor Chart.
6.8 Determinetheperimeteroftheglasslitebyaddingtwice 7.1.4 Glass type,
the width to twice the height.
7.1.5 Glass dimensions,
6.9 Determine the allowable thermal stress, s , from
7.1.6 Edge bite,
allowable
Fig.4usingtheglassperimeterandthespecifiedacceptableP .
7.1.7 Frame type,
b
6.10 If s > s ,P for the glass exceeds the
calculated allowable b 7.1.8 Solar absorptance (A ),
s
specified probability of breakage for the thermal design con-
7.1.9 Solar transmittance (T ),
s
ditions. If P for the glass exceeds the specified probability of
b
7.1.10 Total Solar Reflectance of Shade Device (RSD),
breakage, the user shall consider using strengthened glass,
7.1.11 Incident solar irradiance (I ),
s
modifying the controllable design conditions, or having a more
7.1.12 Acceptable probability of breakage (P ),
b
comprehensive thermal stress analysis performed.
7.1.13 Allowable thermal stress (s ), and
allowable
7.1.14 Calculated thermal stress (s ).
7. Report calculated
7.1.15 Conclusion
7.1 The report shall consist of the design example work-
sheet presented in Fig. 5 or, as a minimum, shall include:
8. Keywords
7.1.1 Project name,
7.1.2 Date, 8.1 annealed glass; thermal stress; thermal breakage; glass;
7.1.3 Project location, flat glass; soda-lime silica glass; thermal load
E2431–06
FIG. 2 Shadow Conditions.
E2431–06
FIG. 3 Solar Load Adjustment Factor, SLA.
FIG. 4 Probability of Breakage (POB) Chart.
E2431–06
DESIGN WORKSHEET FOR THERMAL STRESS EVALUATION
PROJECT: NAME: ______________________DATE:__________________
LOCATION: _______________________________________
Glass Type: _______________________
Glass Dimensions: width _________mm length ____________mm thickness____________mm
Perimeter _____________________m
Edge Bite: ______________________________mm
Frame Type: ___________________________
Solar Absorptance (A __________________
s)
Solar Transmittance (T )________________
s
Solar Reflectance of Shade Device (R )__________________
s
Incident solar irradiance (I )___________________W/m
s
Acceptable Probability of Breakage (P ) _____________
b
Compute Solar Load (SL)
SL = I 3 A = _______ W/m
s s
Determine Edge Thermal Stress Factor: Use Figure 1
TSF = ______________kPa/( W/m )
edge
Shadow Thermal Stress Factor (TSF )__________ kPa/(W/m ) (Use Figure 2 and Table 2)
shadow
Determine Total Thermal Stress Factor (TSF )
total
TSF = TSF + TSF , but no greater than 39.4 kPa/(W/m ) for angular shadows or 32.0
total edge shadow
kPa/(W/m ) for all other shadows.
TSF = ________________ kPa/(W/m )
total
Solar Load Adjustment Factor (SLA)_____________(Use Figure 3)
Determine the Calculated thermal stress,s
calculated
s =(TSF 3 SL 3 SLA)/1000 = ______________MPa
calculated total
Determine allowable thermal stress, s , from Figure 4
allowable
s =_______________MPa
allowable
Conclusion:
If s < s OK
calculated allowable
If s < s NG
calculated allowable
FIG. 5 Design Worksheet for Thermal Stress Evaluation.
E2431–06
APPENDIX
(Nonmandatory Information)
X1. EXAMPLES OF THE USE OF THIS STANDARD PRACTICE
X1.1 This appendix presents two examples of the use of X1.2.9 The allowable thermal stress, s , correspond-
allowable
this standard practice. The first example is typical of a ing to a glas
...