ASTM E1300 09a Example 3: Double glazed unit, 1/4 in tempered over 5/16 in laminated

Inputs

Calculations

Support

Four sides, double glazed insulating glass

Long dimension, a

74.80 in

Short dimension, b

59.84 in

Non factored load (NFL)

52.22 psf

Glass type factor (GTF)

1.90

Load resistance (LR)

140.90 psf

Lite 1: 1/4 in, fully tempered (FT)

Non factored load (NFL)

36.81 psf, E1300 chart

Glass type factor (GTF)

2.85

Load share LS

1.63, Table 5

Load resistance of the lite (LR)

171.01 psf

Share of the design load (p·LSF)

76.88 psf

Load times area squared at the share, (p·LSF)·A²

74.29 kip·ft²

Load resistance of the lite, short duration load

471.42 psf (GTF 3.80, Load share LS 3.37)

Load resistance of the lite, long duration load

171.01 psf (GTF 2.85, Load share LS 1.63)

Deflection of the lite, w

1.134 in, Appendix X2

p̂, x = ln(ln p̂) (at the share of the load)

448.05, 1.81

Modulus of elasticity, E

10,400 ksi

r0, r1, r2 (X2, R capped at 5)

−2.69, 2.01, 0.21

Lite 2: laminated, designation 5/16 in, heat strengthened (HS)

Laminated glass chart

E1300 09a 6.11 to 6.14, Fig A1.29

Non factored load (NFL)

52.22 psf, E1300 chart

Glass type factor (GTF)

1.90

Load share LS

1.42, Table 5

Load resistance of the lite (LR)

140.90 psf, governs the unit

Share of the design load (p·LSF)

88.25 psf

Load times area squared at the share, (p·LSF)·A²

85.28 kip·ft²

Load resistance of the lite, short duration load

140.90 psf (GTF 1.90, Load share LS 1.42)

Load resistance of the lite, long duration load

169.07 psf (GTF 1.25, Load share LS 2.59)

Deflection of the lite, w

0.918 in, Appendix X2

p̂, x = ln(ln p̂) (at the share of the load)

162.15, 1.63

Modulus of elasticity, E

10,400 ksi

r0, r1, r2 (X2, R capped at 5)

−2.69, 2.01, 0.21

E1300 procedure

E1300 09a 6.10, double glazed insulating glass, four sides

Glass type factors

E1300 09a Table 2, Lite 1 FT with Lite 2 HS; E1300 09a Table 3, Lite 1 FT with Lite 2 HS

Load share source

E1300 09a Table 5, printed values (LS multipliers)

Long duration load share source

E1300 09a Table 6 (monolithic lite with laminated lite), printed values

Thickness cubed of each lite

0.010 in³, 0.025 in³

Aspect ratio, AR

1.25

Load times area squared, whole unit, p·A²

121.09 kip·ft²

Governing lite

Lite 2, load resistance 140.90 psf

Largest lite deflection, w (Lite 1)

1.13 in

Allowable deflection

w_allow = b/100 = 59.84/100 = 0.60 in

Deflection to thickness ratio, w/t

5.18

Load share, LS multipliers: E1300 Table 5, E1300 09a Table 5. This is the E1300 value.

Lite 1 non factored load (NFL): E1300 chart, E1300 09a Fig A1.6. 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 A1.29. This is the E1300 value.

Lite 2 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 = 125.31 psf ≤ LR = 140.90 psf; p/LR = 0.89.

Deflection at CoG: w = 1.13 in > w_allow = 0.60 in (b/100, four edges supported).

CoG: center of glass

GlassLoad.com 140.9 psf, printed 141 psf. The standard printed 6.75 kPa. The printed example is a horizontal skylight and subtracts the glass weight. GlassLoad.com calculated the unit as vertical glass, so the glass weight is not subtracted. The printed value is the one before the glass weight.

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.

W25

Appendix X1 is evaluated at the thickness t, the Table 4 minimum of the designation and at the share of p that lite carries, which treats the plies as one lite and ignores the interlayer under a long duration load, so w can be understated. 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.

W18

A laminated lite of two plies with an interlayer is read as its thickness designation by E1300 3.2.4.2. For a long duration load, E1300 6.11 to 6.14 gives the unit the lowest of four values, so check that the designation matches your laminate.

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.