ASTM E1300 24 Example 2: Non factored load of a 50 by 60 in, 1/4 in annealed plate
Find the non factored load (NFL) of a 50 by 60 by 1/4 in monolithic annealed glass plate, in inch pound units.
Inputs
- Long dimension, a
- 60.00 in
- Short dimension, b
- 50.00 in
- Nominal thickness
- 0.236 in
- Glass type
- Annealed (AN)
- Load duration
- Short (3 second)
- Design load, p
- 30.00 psf
- Allowable deflection, w_allow
- b/100
- Glass thickness, t
- 0.219 in
- Thickness source
- Table 4 minimum
Calculations
- Glass area, A
- 20.83 ft²
- Aspect ratio, AR
- 1.20
- Load times area squared, p·A²
- 13.02 kip·ft²
- Non factored load (NFL)
- 50.11 psf
- Glass type factor (GTF)
- 1.00
- Load resistance (LR)
- 50.11 psf
- Nondimensional load, p̂ = p·(a·b)²/(E·t⁴)
- 78.53
- Modulus of elasticity, E
- 10,400 ksi
- x = ln(ln p̂)
- 1.47
- r0 (X1, R capped at 5)
- −2.61
- r1 (X1, R capped at 5)
- 1.94
- r2 (X1, R capped at 5)
- 0.23
- Center of glass deflection, w
- 0.44 in
- Deflection before rounding (E1300 X1.1.1)
- 0.441 in
- Allowable deflection
- w_allow = b/100 = 50.00/100 = 0.50 in
- Deflection to thickness ratio, w/t
- 2.02
- Load duration in Annex A2 (td)
- 3 s, (td / 3 s)^(7/16) = 1.00
- B (Annex A2, Eq A2.2)
- 0.00072
- Pb = 1 − exp(−B)
- 0.00072
NFL and deflection: E1300 24 Fig A1.7 chart.
Contours: NFL in psf, labelled on the chart. 1/4 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.
Redrawn by GlassLoad.com based on the ASTM E1300 24 Figure A1.7 printed chart; results vary by about 0.2 percent.
Outputs
Strength PASS. Deflection PASS.
Probability of breakage at the design load: 0.72 per 1000 (1 in 1,400).
Strength: p = 30.00 psf ≤ LR = 50.11 psf; p/LR = 0.60.
Deflection at CoG: w = 0.44 in ≤ w_allow = 0.50 in (b/100, four edges supported).
CoG: center of glass
GlassLoad.com 50.1 psf, printed 50.2 psf. The example gives no design load. GlassLoad.com used 30 psf. The NFL does not depend on it. The printed 50.2 psf is 2.4 kPa multiplied by 20.9.
Notes
- W7
- Deflection w is read from the E1300 deflection chart and is approximate. 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.
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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