Glass Lite Wind Load, Deflection Limit, and Weight

LOAD is arithmetic -- pressure times area -- and it is what the framing, the anchors, and the structure behind them have to carry. DEFLECTION governs the glazing pocket and the sealant, because a lite that deflects past its bite comes out of the frame whether or not it broke, and the limit is set on the SHORT span, which is where the curvature is. WEIGHT decides handling: a large insulating unit is a two-crew-and-a-vacuum-lifter problem long before it is a structural one, and the suction-cup lifter count is its own calculation here. The fourth line is the honest one. Heat-strengthened glass carries roughly twice the load of annealed at the same thickness and fully tempered roughly four times, so dividing the design pressure by the type factor gives the EQUIVALENT ANNEALED PRESSURE that a load-resistance chart is entered with. That chart is ASTM E1300, it is a copyrighted compilation, and this calculation does not reproduce it -- it gets a reader to the door of the chart with the right number in hand. A 5 by 8 ft lite of quarter-inch glass at 30 psf puts 1,200 lb into the perimeter framing, allows about a third of an inch of center deflection at L/175, and weighs 131 lb as a single lite or about 275 lb as an insulating unit. Then the type factor: at 30 psf design, annealed is charted at 30 psf, heat-strengthened at an equivalent 15, and fully tempered at 7.5, which is usually the difference between a thickness that is available and one that is not. THIS DOES NOT SELECT GLASS THICKNESS. It does not compute design wind pressure, which is an ASCE 7 calculation with its own exposure, height, and component-and-cladding factors, and it does not address glazing bite, setting blocks, edge condition, thermal stress breakage, safety glazing, or laminated interlayer behavior. ASTM E1300, the glass fabricator, the structural engineer, and the AHJ govern.

area = width x height; total design load = area x design pressure; aspect ratio = long / short; allowable deflection = short span x 12 / limit divisor; equivalent annealed pressure = design pressure / glass type factor; lite weight = area x 13.1 x thickness; assembly = lites x that, plus the spacer and sealant allowance.

The ASTM E1300 glass-type strength factors (annealed 1.0, heat-strengthened about 2, fully tempered about 4) and the equivalent-annealed-pressure convention for entering a load-resistance chart, cited by number and linked, with NO E1300 table reproduced. The customary L/175 deflection limit for glass, taken on the short span. Nominal soda-lime float glass weight of about 13.1 lb per sq ft per inch of thickness. This does not select glass thickness; ASTM E1300, the fabricator, the structural engineer, and the AHJ govern.

Load, aspect ratio, deflection, and weight are arithmetic on the user's own dimensions; the type factors are stated values, and the load-resistance charts they feed are cited rather than reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: width_ft, height_ft, design_pressure_psf, glass_type, deflection_divisor, thickness_in, lites, spacer_allowance_psf, area_sqft, total_load_lb, aspect_ratio, allowable_deflection_in, equivalent_annealed_psf, lite_weight_lb, assembly_weight_lb

• Does not select thickness thickness comes from the ASTM E1300 load-resistance charts, which are cited and not reproducedASTM E1300
• Deflection on the short span the L/175 limit is taken on the short dimension, where the curvature isglazing practice
• Design pressure is an input the ASCE 7 component-and-cladding pressure, with internal pressure and debris provisions, is computed elsewhereASCE 7