Which anchoring systems and backup structure considerations ensure structural integrity of curtain wall during seismic events?

Curtain wall anchorage in seismic zones must be designed to accept dynamic displacements and energy without producing brittle failure modes. Anchors should provide a secure load path while permitting relative movement between façade units and the building structure. Typical solutions include slotted anchor holes with oversized fasteners to allow in-plane movement, sliding anchors that bear vertical loads while allowing lateral drift, and flexible bracket systems designed for anticipated seismic displacement. Detail anchors to transfer seismic shear to the primary structure with redundancy, and ensure that anchor locations align with structural backing plates or reinforced concrete/steel members capable of resisting concentrated loads. Backup structure must include load distribution plates or angles to prevent local crushing of the substrate; embed plates or blockout reinforcement at early construction stages to provide predictable anchor zones. Consideration must also be given to the capacity of the curtain wall to accommodate interstory drift without glass breakage: use flexible gaskets, movement joints, and mullion designs that permit rotation. For high seismicity regions, specify testing to ASCE or local seismic standards and engage a structural engineer early to correlate curtain wall connector demands with building seismic design. Where possible, use sacrificial elements or energy-dissipating connectors that can be replaced post-event rather than requiring full façade replacement. Coordination with the main building structural design ensures the backup structure has sufficient stiffness and capacity, preventing anchor pull-out or progressive façade failures during seismic events.