A propped wall solution preserves an Art Deco gem's historic façade while retaining maximum leasable space within.
With its terra cotta and serpentine stone façade, the I. Magnin Building, constructed in 1930, is one of Oakland’s most prominent Art Deco landmarks. The building sat vacant for a few years after the store closed in 1995, but soon a booming commercial office market sparked interest in retrofitting and updating the four-story, steel-frame building for office space.
To preserve the historic façade and retain the maximum leasable space, Tipping Mar designed a propped wall solution that combines friction damping with the best aspects of steel braces and concrete flexural walls. Tall, slender concrete walls are "propped" near the top with multi-story diagonal steel braces. For small, occasional earthquakes, the propped walls remain rigid to protect the historic façade. During a large and rare earthquake, the slotted bolted friction connections of the steel props can slip, absorbing seismic energy through friction. Energy is also dissipated through flexural yielding at the base of the walls.
The resulting high-performance lateral bracing system is more cost-effective and less architecturally intrusive than either steel-braced frames or concrete shear walls acting alone. The propped walls integrate well with the original structure, where the new walls act as rigid spines to eliminate the soft-story failure potential of the existing frames. This “mode shaping” effect heals the frame’s weakness to realize greater strength and stiffness. Employing this system also allowed the owner to retain the maximum amount of open floor space.