How do curtain wall systems perform in seismic zones?

Curtain wall systems in seismic zones are engineered to accommodate building movement during earthquakes without catastrophic failure. The key design principle is **flexibility, not rigidity** — the curtain wall must move with the building structure rather than resist it.

**Seismic performance strategies:**

1. **Inter-story drift accommodation:** Buildings sway horizontally during earthquakes, creating relative displacement between floors (inter-story drift). Curtain walls incorporate:

   - **Slip joints in mullions:** Telescoping connections that allow vertical movement

   - **Horizontal movement joints:** Accommodate lateral drift at each floor level

   - **Split mullion design:** Two-piece mullions with sliding interfaces

2. **Glass retention:** Laminated glass is used in seismic zones because the interlayer (PVB or SGP) holds broken glass in place, preventing falling hazards. Glass panels are also sized with adequate edge clearance to allow frame movement without glass-to-metal contact.

3. **Anchorage flexibility:** Anchors are designed to allow rotation and translation while maintaining structural connection. Slotted anchor holes and flexible bracket designs accommodate multi-directional movement.

4. **Performance testing:** Seismic curtain walls undergo cyclic racking tests (e.g., AAMA 501.6) to verify drift capacity and glass retention under simulated earthquake displacement.

FOWALL's seismic performance solutions are engineered for projects in active seismic regions. Their design team calculates expected inter-story drift from structural engineers' data and specifies appropriate movement joints, glass types, and anchorage systems to ensure life-safety performance during seismic events.