ASTM E1300 09a 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)

27.95 psf

Glass type factor (GTF)

0.81

Load resistance (LR)

54.44 psf

Lite 1: 1/8 in, annealed (AN)

Non factored load (NFL)

27.95 psf, E1300 chart

Glass type factor (GTF)

0.81

Load share LS

2.40, equation

Load resistance of the lite (LR)

54.44 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

0.475 in, Appendix X2

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 (X2, R capped at 5)

−3.02, 2.27, 0.18

Lite 2: 3/32 in, annealed (AN)

Non factored load (NFL)

18.12 psf, E1300 chart

Glass type factor (GTF)

0.81

Load share LS

5.94, equation

Load resistance of the lite (LR)

87.18 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

0.409 in, Appendix X2

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 (X2, R capped at 5)

−3.02, 2.27, 0.18

Lite 3: 1/8 in, annealed (AN)

Non factored load (NFL)

27.95 psf, E1300 chart

Glass type factor (GTF)

0.81

Load share LS

2.40, equation

Load resistance of the lite (LR)

54.44 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

0.475 in, Appendix X2

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 (X2, R capped at 5)

−3.02, 2.27, 0.18

E1300 procedure

E1300 09a 6.15, triple glazed insulating glass, four sides

Glass type factors

E1300 09a Table 7, AN, short duration

Load share source

E1300 09a 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 54.44 psf

Largest lite deflection, w (Lite 1)

0.48 in

Allowable deflection

w_allow = b/100 = 39.37/100 = 0.39 in

Deflection to thickness ratio, w/t

4.13

Load share, LS multipliers: E1300 load share equation, E1300 09a 6.15.3. This is the E1300 value.

Lite 1 non factored load (NFL): E1300 chart, E1300 09a Fig A1.3. This is the E1300 value.

Lite 1 deflection: E1300 Appendix X2. E1300 gives no deflection method for insulating glass.

Lite 2 non factored load (NFL): E1300 chart, E1300 09a Fig A1.1. This is the E1300 value.

Lite 2 deflection: E1300 Appendix X2. E1300 gives no deflection method for insulating glass.

Lite 3 non factored load (NFL): E1300 chart, E1300 09a Fig A1.3. This is the E1300 value.

Lite 3 deflection: E1300 Appendix X2. 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 = 54.44 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 54.4 psf, printed 44.5 psf. The standard printed 2.13 kPa. The printed example reads the NFL of the 1/8 in lite as 23.0 psf and of the 3/32 in lite as 14.6 psf from the charts. The calculated values are 28.0 and 18.4 psf, which later editions print.

Notes

W7

E1300 gives no deflection method for IG, so w of each lite is approximate, from Appendix X2 at the share of p that lite carries. Where deflection governs, verify it by an independent method.

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.