ASTM E1300 12a Example 9: Deflection with a measured thickness, converted from SI
Find the maximum lateral deflection of a vertical 47.24 by 59.06 by 1/4 in plate under 37.59 psf, with a measured thickness of 0.2205 in.
Inputs
- Long dimension, a
- 59.06 in
- Short dimension, b
- 47.24 in
- Nominal thickness
- 0.236 in
- Glass type
- Annealed (AN)
- Load duration
- Short (3 second)
- Design load, p
- 37.59 psf
- Allowable deflection, w_allow
- b/100
- Thickness override
- 0.221 in
- Glass thickness, t
- 0.221 in
- Thickness source
- User entered override
Calculations
- Glass area, A
- 19.38 ft²
- Aspect ratio, AR
- 1.25
- Load times area squared, p·A²
- 14.11 kip·ft²
- Non factored load (NFL)
- 52.33 psf
- Glass type factor (GTF)
- 1.00
- Load resistance (LR)
- 52.33 psf
- Nondimensional load, p̂ = p·(a·b)²/(E·t⁴)
- 82.66
- Modulus of elasticity, E
- 10,400 ksi
- x = ln(ln p̂)
- 1.48
- r0 (X1, R capped at 5)
- −2.69
- r1 (X1, R capped at 5)
- 2.01
- r2 (X1, R capped at 5)
- 0.21
- Center of glass deflection, w
- 0.48 in
- Deflection before rounding (E1300 X1.1.1)
- 0.466 in
- Allowable deflection
- w_allow = b/100 = 47.24/100 = 0.47 in
- Deflection to thickness ratio, w/t
- 2.11
- Load duration in Annex A2 (td)
- 3 s, (td / 3 s)^(7/16) = 1.00
- B (Annex A2, Eq A2.2)
- 0.002
- Pb = 1 − exp(−B)
- 0.002
NFL and deflection are read for the nominal designation 1/4 in; t = 0.221 in is used only by Appendix X1 and the plate solver.
NFL and deflection: E1300 12a Fig A1.6 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 12a Figure A1.6 printed chart; results vary by about 0.0 percent.
Outputs
Strength PASS. Deflection FAIL.
Probability of breakage at the design load: 1.6 per 1000 (1 in 610).
Strength: p = 37.59 psf ≤ LR = 52.33 psf; p/LR = 0.72.
Deflection at CoG: w = 0.48 in > w_allow = 0.47 in (b/100, four edges supported).
CoG: center of glass
GlassLoad.com 0.48 in, printed 0.48 in. The standard printed 12.2 mm. The printed value is from the polynomial of Appendix X1.
Notes
- W3
- Thickness override: t is not the nominal thickness. Check that t is the thickness of the glass you will use.
- 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.
- W14
- This edition has no procedure for Pb, so the value shown uses the failure model of E1300 24 Annex A2. Treat this Pb as approximate.
More examples are on the E1300 12a page and on the examples page. Open the calculator to run your own check.
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