ASTM E1300 16 Example 6: Triple glazed unit, 1/8, 3/32 and 1/8 in annealed lites

Inputs

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 16 6.2.14, triple glazed insulating glass, four sides

Glass type factors

E1300 16 Table 7, AN, short duration

Load share source

E1300 16 6.15.3, 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 16 6.2.14.3. This is the E1300 value.

Lite 1 non factored load (NFL): E1300 chart, E1300 16 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 16 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 16 Fig A1.4. This is the E1300 value.

Lite 3 deflection: E1300 Appendix X1. E1300 gives no deflection method for insulating glass.

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 16 6.3.3, 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.