Significance and Use
This practice is used to determine the LR of specified glass types and constructions exposed to uniform lateral loads.
Use of this practice assumes:
The glass is free of edge damage and is properly glazed,
The glass has not been subjected to abuse,
The surface condition of the glass is typical of glass that has been in service for several years, and is weaker than freshly manufactured glass due to minor abrasions on exposed surfaces,
The glass edge support system is sufficiently stiff to limit the lateral deflections of the supported glass edges to no more than 1/175 of their lengths. The specified design load shall be used for this calculation.
The center of glass deflection will not result in loss of edge support.
Note 1—This practice does not address aesthetic issues caused by glass deflection.
Many other factors shall be considered in glass type and thickness selection. These factors include but are not limited to: thermal stresses, spontaneous breakage of tempered glass, the effects of windborne debris, excessive deflections, behavior of glass fragments after breakage, seismic effects, heat flow, edge bite, noise abatement, potential post-breakage consequences, and so forth. In addition, considerations set forth in building codes along with criteria presented in safety glazing standards and site specific concerns may control the ultimate glass type and thickness selection.
For situations not specifically addressed in this standard, the design professional shall use engineering analysis and judgment to determine the LR of glass in buildings.
Scope
1.1 This practice describes procedures to determine the load resistance (LR) of specified glass types, including combinations of glass types used in a sealed insulating glass (IG) unit, exposed to a uniform lateral load of short or long duration, for a specified probability of breakage.
1.2 This practice applies to vertical and sloped glazing in buildings for which the specified design loads consist of wind load, snow load and self-weight with a total combined magnitude less than or equal to 15 kPa (315 psf). This practice shall not apply to other applications including, but not limited to, balustrades, glass floor panels, aquariums, structural glass members, and glass shelves.
1.3 This practice applies only to monolithic and laminated, glass constructions of rectangular shape with continuous lateral support along one, two, three, or four edges. This practice assumes that (1) the supported glass edges for two, three, and four-sided support conditions are simply supported and free to slip in plane; (2) glass supported on two sides acts as a simply supported beam; and (3) glass supported on one side acts as a cantilever. For insulating glass units, this practice only applies to insulating glass units with four-sided edge support.
1.4 This practice does not apply to any form of wired, patterned, etched, sandblasted, drilled, notched, or grooved glass with surface and edge treatments that alter the glass strength.
1.5 This practice addresses only the determination of the resistance of glass to uniform lateral loads. The final thickness and type of glass selected also depends upon a variety of other factors (see 5.3).
1.6 Charts in this practice provide a means to determine approximate maximum lateral glass deflection. Appendix X1 provides additional procedures to determine maximum lateral deflection for glass simply supported on four sides. Appendix X2 presents a procedure to compute approximate probability of breakage for annealed (AN) monolithic glass lites simply supported on four sides.
1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for mathematical conversions to inch-pound units that are provided for information only and are not considered standard.
1.8 Appendix X3 lists the key variables used in calculating the mandatory type factors in Tables 1-3 and comments on their conservative values.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
TABLE 1 Glass Type Factors (GTF) for a Single Lite of Monolithic or Laminated Glass (LG)
| GTF | ||
|---|---|---|
| Glass Type | Short Duration Load (3 s) | Long Duration Load (30 days) |
| AN | 1.0 | 0.43 |
| HS | 2.0 | 1.3 |
| FT | 4.0 | 3.0 |
TABLE 2 Glass Type Factors (GTF) for Double Glazed Insulating Glass (IG), Short Duration Load
| Lite No. 1 Monolithic Glass or Laminated Glass Type | Lite No. 2 Monolithic Glass or Laminated Glass Type | |||||
|---|---|---|---|---|---|---|
| AN | HS | FT | ||||
| GTF1 | GTF2 | GTF1 | GTF2 | GTF1 | GTF2 | |
| AN | 0.9 | 0.9 | 1.0 | 1.9 | 1.0 | 3.8 |
| HS | 1.9 | 1.0 | 1.8 | 1.8 | 1.9 | 3.8 |
| FT | 3.8 | 1.0 | 3.8 | 1.9 | 3.6 | 3.6 |
TABLE 3 Glass Type Factors (GTF) for Double Glazed Insulating Glass (IG), Long Duration Load (30 day)
| Lite No. 1 Monolithic Glass or Laminated Glass Type | Lite No. 2 Monolithic Glass or Laminated Glass Type | |||||
|---|---|---|---|---|---|---|
| AN | HS | FT | ||||
| GTF1 | GTF2 | GTF1 | GTF2 | GTF1 | GTF2 | |
| AN | 0.39 | 0.39 | 0.43 | 1.25 | 0.43 | 2.85 |
| HS | 1.25 | 0.43 | 1.25 | 1.25 | 1.25 | 2.85 |
| FT | 2.85 | 0.43 | 2.85 | 1.25 | 2.85 | 2.85 |
