Count on Saflex® to Carry the Load
Architectural glazing products are employed in a myriad of situations that require structural design. Windows, spandrel units, skylights, doors, storefronts, atriums, greenhouses, passageways, side lites, and many other uses of glazing each has its own requirements for design. These requirements may involve combinations of loads (wind, snow, dead, live), as well as additional conditions involving earthquakes, human impact, human loads, and hail. Saflex® interlayer for laminated glass helps create solutions for a variety of glazing performance needs while maintaining aesthetic design goals.
Designing for Breakage
If glass breakage presents a hazard or liability to persons below the envelope of a building that has been compromised, laminated glass offers a solution. If breakage occurs, laminated glass made with Saflex interlayer can remain in the window opening because of its inherent retention characteristics after breakage has occurred.
Research shows that laminated glass units are as strong as monolithic glass lites of the same nominal thickness unless adverse environmental conditions exist. Laminate strength may be decreased versus monolithic glass when subjected to certain long-term loads such as snow loads or high heat for extended periods of time. Selection of the proper laminated glass thickness to carry the design load requires following the principles outlined in ASTM E1300.
Laminated architectural glass made with Saflex protective interlayer can meet structural codes and building standards in a variety of applications and designs including:
Overhead Glazing
The three model building codes define "overhead glazing" as glass that is positioned over space that may be occupied by humans. The model codes, in effect, prescribe laminated glass for overhead glazing that is either a single lite or the lower lite in an insulating glass unit. However, other products are allowed provided post breakage controls are in effect (e.g., mesh under tempered lites). Overhead glazing should not be exposed to the weight of a person and should be designed to discourage people from walking on glass surfaces. If necessary, the ability of a lite in an overhead glazing unit to withstand human loads can be checked using the equation for a concentrated load, based on a floor design.
Glass Floors
Laminated glass floors are popular today. Calculations for floor loads can be found in model building codes. When designing glass floors (walking surface of floors, landings, stairwells and similar locations), it is generally recommended that the following criteria be used:
- Laminated glass should have a minimum of three plies and should be capable of supporting the total design load with any one ply broken
- Surface damage caused by people or by objects placed on glass can significantly reduce the strength of glass (subjecting it to breakage under subsequent loads) and should therefore be considered in the design
- Glass floors may be subject to conditions that make them slippery or targets of high-pressure or high-impact loads
Insulated Glass Units (IG)
Insulating glass contains a sealed air space that results in "load sharing" between lites. The lites will share the load equally if the lites in an IG unit are the same type (AN, HS, FT*), are equal in thickness and are relatively thin. If the glass is not symmetrical, then load sharing will not be equal and needs to be calculated to determine the strength of the unit. Insulating units can utilize laminated lites in one or both glass positions. In most applications, when laminated glass is used as only one lite of an insulating system, the laminate should be placed toward the interior of the building. For optimum protection of occupants and from injuries resulting from falling glass, consider use of a double laminated insulating unit.
*AN = Annealed glass, HS = Heat-strengthened glass, FT = Fully Tempered glass.
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