ASTM E1300 24 Example 6: Triple glazed unit, 1/8, 3/32 and 1/8 in annealed lites
Find the load resistance of a vertical triple glazed window of 39.37 by 59.06 in with 1/8 in, 3/32 in and 1/8 in annealed lites under a 31.33 psf short duration load.
Inputs
- Long dimension, a
- 59.06 in
- Short dimension, b
- 39.37 in
- Construction
- Insulating, triple
- Lite 1
- 1/8 in AN
- Lite 2
- 3/32 in AN
- Lite 3
- 1/8 in AN
- Load share form
- LSF fractions
- Unit type
- Triple glazed
- Glass type
- Annealed (AN)
- Load duration
- Short (3 second)
- Design load, p
- 31.33 psf
- Allowable deflection, w_allow
- b/100
Insulating glass
- Construction
- Insulating glass, triple glazed unit of monolithic lites
- Lite 1
- 1/8 in, annealed (AN)
- Lite 1 thickness used
- 0.115 in (Table 4 minimum)
- Lite 2
- 3/32 in, annealed (AN)
- Lite 2 thickness used
- 0.085 in (Table 4 minimum)
- Lite 3
- 1/8 in, annealed (AN)
- Lite 3 thickness used
- 0.115 in (Table 4 minimum)
Calculations
- Support
- Four sides, triple glazed insulating glass
- Long dimension, a
- 59.06 in
- Short dimension, b
- 39.37 in
- Non factored load (NFL)
- 27.78 psf
- Glass type factor (GTF)
- 0.81
- Load resistance (LR)
- 54.11 psf
- Lite 1: 1/8 in, annealed (AN)
- Non factored load (NFL)
- 27.78 psf, E1300 chart
- Glass type factor (GTF)
- 0.81
- Load share LSF
- 0.416, equation
- Load resistance of the lite (LR)
- 54.11 psf, governs the unit
- Share of the design load (p·LSF)
- 13.03 psf
- Load times area squared at the share, (p·LSF)·A²
- 3.40 kip·ft²
- Deflection of the lite, w
- 0.48 in, Appendix X1, rounded from 0.475 in (E1300 X1.1.1)
- p̂, x = ln(ln p̂) (at the share of the load)
- 269.26, 1.72
- Modulus of elasticity, E
- 10,400 ksi
- r0, r1, r2 (X1, R capped at 5)
- −3.02, 2.27, 0.18
- Lite 2: 3/32 in, annealed (AN)
- Non factored load (NFL)
- 17.96 psf, E1300 chart
- Glass type factor (GTF)
- 0.81
- Load share LSF
- 0.168, equation
- Load resistance of the lite (LR)
- 86.45 psf
- Share of the design load (p·LSF)
- 5.27 psf
- Load times area squared at the share, (p·LSF)·A²
- 1.37 kip·ft²
- Deflection of the lite, w
- 0.40 in, Appendix X1, rounded from 0.409 in (E1300 X1.1.1)
- p̂, x = ln(ln p̂) (at the share of the load)
- 364.00, 1.77
- Modulus of elasticity, E
- 10,400 ksi
- r0, r1, r2 (X1, R capped at 5)
- −3.02, 2.27, 0.18
- Lite 3: 1/8 in, annealed (AN)
- Non factored load (NFL)
- 27.78 psf, E1300 chart
- Glass type factor (GTF)
- 0.81
- Load share LSF
- 0.416, equation
- Load resistance of the lite (LR)
- 54.11 psf
- Share of the design load (p·LSF)
- 13.03 psf
- Load times area squared at the share, (p·LSF)·A²
- 3.40 kip·ft²
- Deflection of the lite, w
- 0.48 in, Appendix X1, rounded from 0.475 in (E1300 X1.1.1)
- p̂, x = ln(ln p̂) (at the share of the load)
- 269.26, 1.72
- Modulus of elasticity, E
- 10,400 ksi
- r0, r1, r2 (X1, R capped at 5)
- −3.02, 2.27, 0.18
- E1300 procedure
- E1300 24 7.2.14, triple glazed insulating glass, four sides
- Glass type factors
- E1300 24 Table 7, AN, short duration
- Load share source
- E1300 24 7.2.14.3, t cubed of each lite over the sum
- Thickness cubed of each lite
- 0.002 in³, 0.00061 in³, 0.002 in³
- Aspect ratio, AR
- 1.50
- Load times area squared, whole unit, p·A²
- 8.17 kip·ft²
- Governing lite
- Lite 1, load resistance 54.11 psf
- Largest lite deflection, w (Lite 1)
- 0.48 in
- Deflection before rounding (E1300 X1.1.1)
- 0.475 in
- Allowable deflection
- w_allow = b/100 = 39.37/100 = 0.39 in
- Deflection to thickness ratio, w/t
- 4.13
Load share, LSF fractions: E1300 load share equation, E1300 24 7.2.14.3. This is the E1300 value.
Lite 1 non factored load (NFL): E1300 chart, E1300 24 Fig A1.4. This is the E1300 value.
Lite 1 deflection: E1300 Appendix X1. E1300 gives no deflection method for insulating glass.
Lite 2 non factored load (NFL): E1300 chart, E1300 24 Fig A1.2. This is the E1300 value.
Lite 2 deflection: E1300 Appendix X1. E1300 gives no deflection method for insulating glass.
Lite 3 non factored load (NFL): E1300 chart, E1300 24 Fig A1.4. This is the E1300 value.
Lite 3 deflection: E1300 Appendix X1. E1300 gives no deflection method for insulating glass.
Contours: NFL in psf, labelled on the chart. 1/8 in glass, four sides simply supported, 3 second load.
Glass sizes where the NFL is above 315 psf, result outside the scope of ASTM E1300.
Curves: center of glass deflection w for aspect ratio (AR) 1 to 5; highlighted: this aspect ratio.
Contours: NFL in psf, labelled on the chart. 3/32 in glass, four sides simply supported, 3 second load.
Glass sizes where the NFL is above 315 psf, result outside the scope of ASTM E1300.
Curves: center of glass deflection w for aspect ratio (AR) 1 to 5; highlighted: this aspect ratio.
Point at the share of the load on this lite, (p·LSF)·A².
Redrawn by GlassLoad.com based on the ASTM E1300 24 Figure A1.4 printed chart; results vary by about 0.7 percent.
Redrawn by GlassLoad.com based on the ASTM E1300 24 Figure A1.2 printed chart; results vary by about 0.9 percent.
Lite 3 is the same as Lite 1.
Outputs
Strength PASS. Deflection FAIL.
Probability of breakage at the design load: not available for insulating glass.
Strength: p = 31.33 psf ≤ LR = 54.11 psf; p/LR = 0.58.
Deflection at CoG: w = 0.48 in > w_allow = 0.39 in (b/100, four edges supported).
CoG: center of glass
GlassLoad.com 54.1 psf, printed 54.5 psf. The standard printed 2.61 kPa.
Notes
- W7
- E1300 gives no deflection method for IG, so w of each lite is approximate, from Appendix X1 at the share of p that lite carries. Where deflection governs, verify it by an independent method.
- W10
- w is greater than t, so it is rounded to the nearest 0.04 in as E1300 requires. Where the rounding affects the outcome, verify the unrounded w independently.
- W6
- No Pb is reported for IG, because E1300 gives Pb of IG only in the analytical procedure of E1300 24 7.3.3, which GlassLoad.com does not run. Where Pb is required, calculate it by that procedure.
- W27
- Load sharing uses the load share factors LS, which are approximate, and pressure changes in the air space from temperature and altitude are not included. If the unit is at high altitude or sees large temperature changes, check the air space pressure separately.
- W29
- E1300 recommends a combined air space width of at most 1.00 in for a triple unit. The air spaces are not given, so this is not checked and you should check the combined width yourself.
More examples are on the E1300 24 page and on the examples page. Open the calculator to run your own check.
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