Seismic Movements

A common building upgrade to add value to existing commercial real estate is the renewal of the entrance lobby. The lobby facade is replaced to give the building a contemporary or less dated appearance. Under seismic loads the existing building structure undergoes significant inter-story drift. The existing facade generally can’t accommodate the level of deformation that comes with the inter-story drift, while the new facade should. Therefore the interface between existing facade and new facade need design attention from both an engineering and an architectural point of view.

The required structural performance for the new facade system is driven by an allowable limit on the damage to the facade elements resulting from elastic building movements due to seismic activity, and an allowable limit to the damage to the facade elements resulting from in-elastic building movements due to seismic.

Varying movement strategies are discussed for both the new facades and the interfaces to the existing building and provides case studies that demonstrate the applicability of the movement strategies. Standard movement joints can be unsightly and hard to incorporate into the Architecture in an elegant way.

Conclusions are that addressing seismic design criteria for facades from the start of the design process helps to apply an effective mitigation strategy; and that when addressed timely and with rigor the story drift requirements of seismic events do not prevent an elegant facade design that meets both the Architectural design and the budget requirements.