ASTM E998-05(2011)
(Test Method)Standard Test Method for Structural Performance of Glass in Windows, Curtain Walls, and Doors Under the Influence of Uniform Static Loads by Nondestructive Method
Standard Test Method for Structural Performance of Glass in Windows, Curtain Walls, and Doors Under the Influence of Uniform Static Loads by Nondestructive Method
SIGNIFICANCE AND USE
This test method is a standard procedure to determine a stress pattern and estimate a probability of breakage of glass tested under uniform static loads.
Loads on glass in windows, curtain walls, and doors may vary greatly in magnitude, direction, and duration. An understanding of wind loads on the building is required for selection of test loads and interpretation of results with respect to expected exposure at a particular site.
The strength of glass varies with many different factors including surface condition, load duration, geometry, relative humidity, and temperature (1, 2, 3, 4).
A thorough understanding of the variations of the strength of glass and the nature of loading is required to interpret results of this test method.
The proper use of this test method requires a knowledge of the principles of pressure, deflection and strain measurement, stress/strain relationships, and statistical estimating techniques.
SCOPE
1.1 This test method is a nondestructive test procedure to establish the nature of stresses induced in glass subjected to uniform static loads. A procedure is provided for using this stress information to estimate the probability of breakage of the glass.
1.2 This test method is applicable to glass of various degrees of temper; for example, annealed, heat-strengthened, fully tempered, laminated, insulating, and combinations thereof.
1.3 This test method describes a process of applying specific test loads to glass. The test may be conducted using the standard test frame specified herein or a test frame of the user's design.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements see Section 6.
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Designation: E998 – 05 (Reapproved 2011)
Standard Test Method for
Structural Performance of Glass in Windows, Curtain Walls,
and Doors Under the Influence of Uniform Static Loads by
Nondestructive Method
This standard is issued under the fixed designation E998; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 coeffıcient of variation—the ratio (decimal fraction) of
the standard deviation of the maximum principal tensile stress
1.1 This test method is a nondestructive test procedure to
(MPTS) at failure to the ABS.
establish the nature of stresses induced in glass subjected to
2.4 equivalent design load—a magnitude of a uniform load
uniform static loads. A procedure is provided for using this
and the load duration selected by the specifying authority to
stressinformationtoestimatetheprobabilityofbreakageofthe
represent design loads.
glass.
2.5 glass specimen—the glass to be tested, for example, a
1.2 This test method is applicable to glass of various
single lite, an insulating glass unit, laminated glass, and so
degrees of temper; for example, annealed, heat-strengthened,
forth (does not include test frame).
fully tempered, laminated, insulating, and combinations
2.6 maximum principal tensile stress (MPTS)—amaximum
thereof.
calculated tensile stress based on strain gage measurements.
1.3 Thistestmethoddescribesaprocessofapplyingspecific
2.7 negative load—aloadthatresultsintheindoorsideofa
test loads to glass. The test may be conducted using the
glass specimen being the high-pressure side.
standardtestframespecifiedhereinoratestframeoftheuser’s
2.8 permanent set of test frame—a load-induced permanent
design.
displacement from an original position of the test frame.
1.4 The values stated in SI units are to be regarded as
2.9 positive load—a load that results in the outdoor side of
standard. The values given in parentheses are mathematical
a glass specimen being the high-pressure side.
conversions to inch-pound units that are provided for informa-
2.10 probability of breakage—the probability that a glass
tion only and are not considered standard.
specimenbreakswhentestedatagivenequivalentdesignload.
1.5 This standard does not purport to address all of the
General industry practice to express probability as lites per
safety problems, if any, associated with its use. It is the
1000 lites.
responsibility of the user of this standard to establish appro-
2.11 residual stress—an initial, state of stress on unloaded,
priate safety and health practices and determine the applica-
unglazedglassresultingfromthemanufacturingprocess(heat-
bility of regulatory limitations prior to use. For specific
strengthening, tempering).
precautionary statements see Section 6.
2.12 specifying authority—the professional or professionals
2. Terminology
responsible for determining and furnishing the information
required to perform this test method as described in Section 9.
2.1 aspect ratio—a ratio of long side to short side of the
glass lite.
3. Summary of Test Method
2.2 average breaking stress (ABS)—the average maximum
3.1 This test method consists of:
principal tensile stress (MPTS) at failure, representative of the
3.1.1 Glazing the test specimen into a test frame that is
glass under test.TheABS is dependent on a number of factors
mounted on or against a test chamber.
including geometry, time history of load, surface condition,
3.1.2 Supplyingorexhaustingairfromthechamberatarate
and so forth. Glasses with residual surface stresses, such as
required to maintain a test-pressure difference across the test
heat-strengthened or fully tempered, must have their residual
specimen.
stresses added to the state of stress at the specified load. As
3.1.3 Measuring and observing deflections, deformations,
defined for use in the standard, theABS is for annealed glass.
specimen strains, and the nature of any failures.
3.1.4 Recording the results in an orderly manner.
This test method is under the jurisdiction of ASTM Committee E06 on
3.2 Methods of loading to nondestructive levels are pro-
Performance of Buildings and is the direct responsibility of Subcommittee E06.51
on Performance of Windows, Doors, Skylights and Curtain Walls. vided.
Current edition approved Oct. 1, 2011. Published October 2011. Originally
3.3 Test data are used to predict glass structural perfor-
approved in 1984. Last previous edition approved in 2005 as E998–05. DOI:
mance characteristics.
10.1520/E0998-05R11.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E998 – 05 (2011)
4. Significance and Use 5.2.7 Temperature Measuring Apparatus, to measure the
ambient temperature within an accuracy of 60.6°C (1°F).
4.1 This test method is a standard procedure to determine a
5.2.8 Relative Humidity Measuring Apparatus, to measure
stress pattern and estimate a probability of breakage of glass
the relative humidity within an accuracy of 62%.
tested under uniform static loads.
4.2 Loads on glass in windows, curtain walls, and doors
6. Safety Precautions
may vary greatly in magnitude, direction, and duration. An
6.1 Proper precautions to protect observers in the event of
understanding of wind loads on the building is required for
glass specimen failure shall be observed.At the pressures used
selection of test loads and interpretation of results with respect
in this test method, considerable energy and hazard are
to expected exposure at a particular site.
involved. In cases of breakage, the hazard to personnel is less
4.3 The strength of glass varies with many different factors
with an exhaust system, as the specimen will tend to blow into
including surface condition, load duration, geometry, relative
2 rather than out of the test chamber. No personnel shall be
humidity, and temperature (1, 2, 3, 4).
permitted in such chambers during tests. All reasonable pre-
4.4 A thorough understanding of the variations of the
cautions shall be exercised during conduct of the test.
strength of glass and the nature of loading is required to
interpret results of this test method.
7. Sampling and Glass Specimens
4.5 Theproperuseofthistestmethodrequiresaknowledge
7.1 Surfacecondition,cutting,fabrication,andpackagingof
of the principles of pressure, deflection and strain measure-
the glass specimens to be tested shall be representative of the
ment,stress/strainrelationships,andstatisticalestimatingtech-
glass whose strength is to be evaluated.
niques.
7.2 All glass specimens shall be visually inspected for edge
or surface irregularities prior to testing, and all questionable
5. Apparatus
glass specimens shall not be tested. All questionable glass
5.1 The description of apparatus is general in nature. Any
specimens shall be reported to the specifying authority.
equipment capable of performing the test procedure within the
7.3 Glass specimens shall be handled carefully at all times
allowable tolerances shall be permitted.
because the strength of glass is influenced by its surface and
5.2 Major Components:
edge conditions.
5.2.1 Test Frame,inwhichglassspecimensaremountedfor
testing. The test frame shall provide either standardized sup-
8. Calibration
port conditions or specified support conditions. Specifications
8.1 Pressure-measuring systems, deflection-measuring de-
of standardized support conditions are presented inAnnexA1.
vices,andstraingagesshallberoutinelychecked.Ifcalibration
5.2.2 Test Chamber, sealed, with an opening in which or
is required, the manufacturer’s recommendations or good
against which the test frame shall be installed. At least one
engineering practice shall be followed.
static pressure tap shall be provided to measure the test
chamber pressure and shall be so located that the reading is
9. Required Information
minimally affected by the velocity of the air supply to or from
9.1 The specifying authority shall provide the magnitude of
the test chamber or any other air movement. The air supply
the equivalent design load (positive or negative) and the
opening into the test chamber shall be arranged so that the air
allowable probability of breakage for the glass specimens.
does not impinge directly on the glass specimen with any
9.2 The specifying authority shall state whether the glass
significant velocity. A means of access into the test chamber
specimens shall be glazed in a standard test frame or in a test
shall be permitted to facilitate adjustments and observations
framedesignedtosimulateaspecificglazingsystem.Ifthetest
after the specimen has been installed.
frame is to simulate a specific glazing system, complete
5.2.3 Air System, a controllable blower, compressed air
glazing details and support conditions shall be provided by the
supply, exhaust system, reversible blower or other device
specifying authority.
designed to apply the equivalent design load to the glass
specimen with required control.
10. Procedure
5.2.4 Pressure Measuring Apparatus, to record continu-
10.1 Measure and record ambient temperature and the
ously the test chamber pressure within an accuracy of 62%.
relative humidity.
5.2.5 Deflection-Measuring System, for measuring deflec-
10.2 Installstraingagestothelowpressuresideoftheglass
tions within an accuracy of 60.25 mm (0.01 in.).
specimen according to procedures in Annex A2.
5.2.5.1 The deflection indicator shall be mounted so that
10.3 Install glass specimens in the test frame in accordance
deflection of the test chamber or test frame is not included in
with recommendations in Annex A1 for standard support
thedeflectiongagereading.Provisionsshallbemadetoensure
conditions or as specified for a specific glazing system by the
that readings can be made from a safe location.
manufacturer.
5.2.6 Strain Gage Measurements—Appendix X1 describes
10.4 Record reference strain reading at no-load conditions.
apparatus and techniques required for proper strain measure-
10.5 Load specimen to low level pressure, 20% of design
ments on glass.
load for 1 min. Release load. Allow 3 to 5-min gage and
restoration time.
10.6 Applyone-halfofthespecifieddesignloadtotheglass
The boldface numbers in parentheses refer to the references listed at the end of
this test method. specimen. Take initial set of pressure, deflection, and strain
E998 – 05 (2011)
readings at one-half of design load. Reduce the test pressure to performance of the glass. For new glass, the ABS shall be
0, and vent the test chamber for a period of 3 to 5 min before obtained from the appropriate glass manufacturer for the glass
pressure-measuring apparatus is adjusted to zero. in question. For glass that has been in service, or treated by
10.6.1 If air leakage around the test specimen is excessive, others (weathered, altered, damaged, scratched, or mechani-
tapeshallbepermittedtobeusedtocoveranycracksandjoints callyaltered)engineeringjudgementshallbeusedtodetermine
through which the leakage is occurring. Tape shall not be used theABS.Theareaoftheglassliteandthedurationofimposed
when there is a probability that it may significantly restrict load affect theABS. The magnitude of the load duration effect
differential movement between the glass and test frame. can be roughly approximated by using Eq X1.1 in Appendix
10.7 Apply load to the glass specimen in increments of X1.
20%ofspecifieddesignload,recordingstraingagereadingsat 12.3 Probability of Breakage—Once glass ABS is estab-
each increment. Maintain the load at each increment of design
lished (ProcedureA), the normal probability distribution func-
load until all strain gage readings are taken. For each incre- tion is used to predict probability of breakage. The probability
ment, the load should not be applied for a period under 1 min
of breakage for glass is calculated as follows:
orlongerthan5mininduration.Continuousload-timerecords
Area 5 Pr~Z$ z ! (1)
o
shall be kept for the duration of the loading.
X 2 ABS
10.8 If the specimen breaks prior to reaching the specified
Z 5
o
CV 3 ABS
design load, check for permanent set of the test frame and
chamber damage before testing another specimen.
where:
X = maximumglasstensionstressresultingfromspeci-
11. Report
fied or test wind load, MPa (psi),
11.1 The report shall include the following information:
ABS = glass ABS, MPa (psi),
11.1.1 Date of the test, the date of the report, the ambient CV = coefficient of variation, 0.22 for annealed glass,
temperature, and the relative humidity. and
Z = standard normal variable (see Table X1.2).
11.1.2 Identification of the glass specimens (manufacturer,
o
source of supply, dimensions, both nominal and measured,
Using the standard normal distribution table, the area to the
manufacturer’s designation, materials, and other pertinent rightofthe Z indicatestheprobabilityofbreakageatthatlevel
o
information).
(see Table X1.2).
11.1.3 Detailed drawings of the glass specimen, test frame,
NOTE 1—Glasses with residual surface stresses, such as heat-
test chamber, a complete description of pressure-measuring
strengthened or fully tempered, shall have their residual stresses added to
apparatus, all other instrumentation, and a statement that the
the state of stress at the specified load. For example, the state of stress of
test was conducted using a standard test frame or a test frame
a heat-strengthened glass surface is 35 MPa (5000 psi) at design load, if
of the user’s design. the glass has a residual compressive stress on the surface of 24 MPa
(−3500 psi), the resulting tensile stress component is 10 MPa (1500 psi)
11.1.4 Records of pressure differences exerted across each
at design load.
glass specimen during the test with each specimen being
NOTE 2—Load/stress relationships for large deflections in glass may be
properly identified.
adequately defined by finite-element computer techniques. The values
11.1.5 Probability of breakage (Z ) as calculated in Section
o
obtained by this technique will be useful for defining probability of
12 (Analysis).
breakage estimates at various load/glass stress combinations.
11.1.6 Identification or description of any applicable speci-
fication.
13. Precision and Bias
11.1.7 A statement that the tests were conducted in accor-
13.1 No statement is made about either the precision or the
dance with this test method, or a full description of any
bias of this test method for measuring the structural perfor-
deviations.
mance of glass since the result merely states whether the
probability of breakage of the glass specimens is significantly
12. Analysis
greater than the specified probability of breakage or not.
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E998–05 Designation: E998 – 05 (Reapproved 2011)
Standard Test Method for
Structural Performance of Glass in Windows, Curtain Walls,
and Doors Under the Influence of Uniform Static Loads by
Nondestructive Method
This standard is issued under the fixed designation E998; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method is a nondestructive test procedure to establish the nature of stresses induced in glass subjected to uniform
static loads. A procedure is provided for using this stress information to estimate the probability of breakage of the glass.
1.2 This test method is applicable to glass of various degrees of temper; for example, annealed, heat-strengthened, fully
tempered, laminated, insulating, and combinations thereof.
1.3 This test method describes a process of applying specific test loads to glass. The test may be conducted using the standard
test frame specified herein or a test frame of the user’s design.
1.4The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions
to inch-pound units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For specific precautionary statements see Section 6.
2. Terminology
2.1 aspect ratio—a ratio of long side to short side of the glass lite.
2.2 average breaking stress (ABS)—theaveragemaximumprincipaltensilestress(MPTS)atfailure,representativeoftheglass
under test.TheABS is dependent on a number of factors including geometry, time history of load, surface condition, and so forth.
Glasses with residual surface stresses, such as heat-strengthened or fully tempered, must have their residual stresses added to the
state of stress at the specified load. As defined for use in the standard, the ABS is for annealed glass.
2.3 coeffıcient of variation—the ratio (decimal fraction) of the standard deviation of the maximum principal tensile stress
(MPTS) at failure to the ABS.
2.4 equivalent design load—a magnitude of a uniform load and the load duration selected by the specifying authority to
represent design loads.
2.5 glass specimen—theglasstobetested,forexample,asinglelite,aninsulatingglassunit,laminatedglass,andsoforth(does
not include test frame).
2.6 maximum principal tensile stress (MPTS)— a maximum calculated tensile stress based on strain gage measurements.
2.7 negative load—a load that results in the indoor side of a glass specimen being the high-pressure side.
2.8 permanent set of test frame—a load-induced permanent displacement from an original position of the test frame.
2.9 positive load—a load that results in the outdoor side of a glass specimen being the high-pressure side.
2.10 probability of breakage—the probability that a glass specimen breaks when tested at a given equivalent design load.
General industry practice to express probability as lites per 1000 lites.
2.11 residual stress—an initial, state of stress on unloaded, unglazed glass resulting from the manufacturing process
(heat-strengthening, tempering).
2.12 specifying authority—theprofessionalorprofessionalsresponsiblefordeterminingandfurnishingtheinformationrequired
to perform this test method as described in Section 9.
3. Summary of Test Method
3.1 This test method consists of:
ThistestmethodisunderthejurisdictionofASTMCommitteeE06onPerformanceofBuildingsandisthedirectresponsibilityofSubcommitteeE06.51onPerformance
of Windows, Doors, Skylights and Curtain Walls.
Current edition approved Oct. 1, 2005.2011. Published November 2005.October 2011. Originally approved in 1984. Last previous edition approved in 19992005 as
E998–84(1999).E998–05. DOI: 10.1520/E0998-05R11.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E998 – 05 (2011)
3.1.1 Glazing the test specimen into a test frame that is mounted on or against a test chamber.
3.1.2 Supplying or exhausting air from the chamber at a rate required to maintain a test-pressure difference across the test
specimen.
3.1.3 Measuring and observing deflections, deformations, specimen strains, and the nature of any failures.
3.1.4 Recording the results in an orderly manner.
3.2 Methods of loading to nondestructive levels are provided.
3.3 Test data are used to predict glass structural performance characteristics.
4. Significance and Use
4.1 This test method is a standard procedure to determine a stress pattern and estimate a probability of breakage of glass tested
under uniform static loads.
4.2 Loads on glass in windows, curtain walls, and doors may vary greatly in magnitude, direction, and duration. An
understanding of wind loads on the building is required for selection of test loads and interpretation of results with respect to
expected exposure at a particular site.
4.3 The strength of glass varies with many different factors including surface condition, load duration, geometry, relative
humidity, and temperature (1, 2, 3, 4).
4.4 Athorough understanding of the variations of the strength of glass and the nature of loading is required to interpret results
of this test method.
4.5 The proper use of this test method requires a knowledge of the principles of pressure, deflection and strain measurement,
stress/strain relationships, and statistical estimating techniques.
5. Apparatus
5.1 The description of apparatus is general in nature. Any equipment capable of performing the test procedure within the
allowable tolerances shall be permitted.
5.2 Major Components:
5.2.1 Test Frame, in which glass specimens are mounted for testing. The test frame shall provide either standardized support
conditions or specified support conditions. Specifications of standardized support conditions are presented in Annex A1.
5.2.2 Test Chamber, sealed, with an opening in which or against which the test frame shall be installed. At least one static
pressure tap shall be provided to measure the test chamber pressure and shall be so located that the reading is minimally affected
by the velocity of the air supply to or from the test chamber or any other air movement. The air supply opening into the test
chamber shall be arranged so that the air does not impinge directly on the glass specimen with any significant velocity.Ameans
of access into the test chamber shall be permitted to facilitate adjustments and observations after the specimen has been installed.
5.2.3 Air System, a controllable blower, compressed air supply, exhaust system, reversible blower or other device designed to
apply the equivalent design load to the glass specimen with required control.
5.2.4 Pressure Measuring Apparatus, to record continuously the test chamber pressure within an accuracy of 62%.
5.2.5 Deflection-Measuring System, for measuring deflections within an accuracy of 60.25 mm (0.01 in.).
5.2.5.1 The deflection indicator shall be mounted so that deflection of the test chamber or test frame is not included in the
deflection gage reading. Provisions shall be made to ensure that readings can be made from a safe location.
5.2.6 Strain Gage Measurements—Appendix X1 describes apparatus and techniques required for proper strain measurements
on glass.
5.2.7 Temperature Measuring Apparatus, to measure the ambient temperature within an accuracy of 60.6°C (1°F).
5.2.8 Relative Humidity Measuring Apparatus, to measure the relative humidity within an accuracy of 62%.
6. Safety Precautions
6.1 Proper precautions to protect observers in the event of glass specimen failure shall be observed. At the pressures used in
thistestmethod,considerableenergyandhazardareinvolved.Incasesofbreakage,thehazardtopersonnelislesswithanexhaust
system,asthespecimenwilltendtoblowintoratherthanoutofthetestchamber.Nopersonnelshallbepermittedinsuchchambers
during tests. All reasonable precautions shall be exercised during conduct of the test.
7. Sampling and Glass Specimens
7.1 Surfacecondition,cutting,fabrication,andpackagingoftheglassspecimenstobetestedshallberepresentativeoftheglass
whose strength is to be evaluated.
7.2 All glass specimens shall be visually inspected for edge or surface irregularities prior to testing, and all questionable glass
specimens shall not be tested. All questionable glass specimens shall be reported to the specifying authority.
7.3 Glass specimens shall be handled carefully at all times because the strength of glass is influenced by its surface and edge
conditions.
The boldface numbers in parentheses refer to the references listed at the end of this test method.
E998 – 05 (2011)
8. Calibration
8.1 Pressure-measuring systems, deflection-measuring devices, and strain gages shall be routinely checked. If calibration is
required, the manufacturer’s recommendations or good engineering practice shall be followed.
9. Required Information
9.1 The specifying authority shall provide the magnitude of the equivalent design load (positive or negative) and the allowable
probability of breakage for the glass specimens.
9.2 The specifying authority shall state whether the glass specimens shall be glazed in a standard test frame or in a test frame
designed to simulate a specific glazing system. If the test frame is to simulate a specific glazing system, complete glazing details
and support conditions shall be provided by the specifying authority.
10. Procedure
10.1 Measure and record ambient temperature and the relative humidity.
10.2 Install strain gages to the low pressure side of the glass specimen according to procedures in Annex A2.
10.3 InstallglassspecimensinthetestframeinaccordancewithrecommendationsinAnnexA1forstandardsupportconditions
or as specified for a specific glazing system by the manufacturer.
10.4 Record reference strain reading at no-load conditions.
10.5 Load specimen to low level pressure, 20% of design load for 1 min. Release load.Allow 3 to 5-min gage and restoration
time.
10.6 Applyone-halfofthespecifieddesignloadtotheglassspecimen.Takeinitialsetofpressure,deflection,andstrainreadings
at one-half of design load. Reduce the test pressure to 0, and vent the test chamber for a period of 3 to 5 min before
pressure-measuring apparatus is adjusted to zero.
10.6.1 If air leakage around the test specimen is excessive, tape shall be permitted to be used to cover any cracks and joints
through which the leakage is occurring. Tape shall not be used when there is a probability that it may significantly restrict
differential movement between the glass and test frame.
10.7 Apply load to the glass specimen in increments of 20% of specified design load, recording strain gage readings at each
increment.Maintaintheloadateachincrementofdesignloaduntilallstraingagereadingsaretaken.Foreachincrement,theload
should not be applied for a period under 1 min or longer than 5 min in duration. Continuous load-time records shall be kept for
the duration of the loading.
10.8 If the specimen breaks prior to reaching the specified design load, check for permanent set of the test frame and chamber
damage before testing another specimen.
11. Report
11.1 The report shall include the following information:
11.1.1 Date of the test, the date of the report, the ambient temperature, and the relative humidity.
11.1.2 Identification of the glass specimens (manufacturer, source of supply, dimensions, both nominal and measured,
manufacturer’s designation, materials, and other pertinent information).
11.1.3 Detailed drawings of the glass specimen, test frame, test chamber, a complete description of pressure-measuring
apparatus, all other instrumentation, and a statement that the test was conducted using a standard test frame or a test frame of the
user’s design.
11.1.4 Records of pressure differences exerted across each glass specimen during the test with each specimen being properly
identified.
11.1.5 Probability of breakage (Z ) as calculated in Section 12 (Analysis).
o
11.1.6 Identification or description of any applicable specification.
11.1.7 A statement that the tests were conducted in accordance with this test method, or a full description of any deviations.
12. Analysis
12.1 An analysis of the structural performance of the glass specimen(s) shall be made.
12.2 Procedure A:
12.2.1 Calculate maximum principal stress from strain gage data (see Appendix X1).
12.2.2 Average Breaking Strength of Glass (ABS)—The ABSisanecessaryvalueforuseinanalyzingthestructuralperformance
of the glass. For new glass, the ABS shall be obtained from the appropriate glass manufacturer for the glass in question. For glass
that has been in service, or treated by others (weathered, altered, damaged, scratched, or mechanically altered) engineering
judgement shall be used to determine the ABS. The area of the glass lite and the duration of imposed load affect the ABS. The
magnitude of the load duration effect can be roughly approximated by using Eq X1.1 in Appendix X1.
12.3 Probability of Breakage—Onceglass ABSisestablished(ProcedureA),thenormalprobabilitydistributionfunctionisused
to predict probability of breakage. The probability of breakage for glass is calculated as follows:
Area 5 Pr~Z$ z ! (1)
o
E998 – 05 (2011)
X 2 ABS
Z 5
o
CV 3 ABS
where:
X = maximum glass tension stress resulting from specified or test wind load, MPa (psi),
ABS = glass ABS, MPa (psi),
CV = coefficient of variation, 0.22 for annealed glass, and
Z = standard normal variable (see Table X1.2).
o
Using the standard normal distribution table, the area to the right of the Z indicates the probability of breakage at that level
o
(see Table X1.2).
NOTE 1—Glasseswithresidualsurfacestresses,suchasheat-strengthenedorfullytempered,shallhavetheirresidualstressesaddedtothestateofstress
at the specified load. For example, the state of stress of a heat-strengthened glass surface is 35 MPa (5000 ps
...
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