Sloped Glazing, Skylights & Overhead
Deflection limits, impact-resistant glazing, bullet-resistant glass, skylights, sloped glazing, and overhead safety requirements.
- Explain glass deflection limits and structural design considerations
- Describe impact-resistant and bullet-resistant glazing types
- Identify sloped and overhead glazing safety requirements
- State the laminated glass requirement for overhead applications
- Explain skylight installation and weatherproofing requirements
Leçon 1
Glass Deflection Limits & Structural Design
What Is Glass Deflection?
Deflection is the amount a glass panel bends under wind load or other forces. Excessive deflection can cause seal failure in IGUs, gasket displacement, and occupant discomfort (visible glass movement). Building codes and glass manufacturers specify maximum deflection limits.
Deflection Limits
The standard deflection limit is L/175, where L is the unsupported span length. For a 70-inch span: 70/175 = 0.4 inches maximum deflection.
For insulating glass units, deflection must also be limited to prevent:
- Seal fatigue leading to premature failure
- Glass-to-glass contact at the center of the unit
- Visible distortion that is unacceptable to occupants
Factors Affecting Glass Strength
| Factor | Effect on Strength |
|---|---|
| Thickness | Thicker = stronger (by cube of thickness) |
| Edge quality | Better edges = less stress concentration |
| Glass type | Tempered > Heat-strengthened > Annealed |
| Support | 4-side > 3-side > 2-side |
| Aspect ratio | Square is stronger than narrow rectangle |
Maximum deflection is typically L/175 of the unsupported span. IGU deflection must prevent seal fatigue and glass-to-glass contact. Glass strength depends on thickness, edge quality, glass type, and support conditions.