Seismic Strengthening of a 19th Century Banking Temple

Abstract eng:
Abandoned by its namesake and left to the pigeons in the 1980s, the Hibernia Bank Building (circa 1892) was used briefly by the San Francisco Police Department as a substation in one of its most colorful neighborhoods: the Tenderloin. The police left in the year 2000 and the “banking temple” was left to sit vacant for another decade. Things seem to be improving for this San Francisco City Landmark, not only is the neighborhood (now coined “mid-Market”) slated for improvements, but the new owners of the building have just completed an ambitious renovation including seismic strengthening. WJE’s retrofit concept was designed in deference to the structural mechanism of rocking that allowed the unreinforced masonry building to survive the ground shaking associated with the 1906 earthquake relatively unscathed, although the building was later ravaged by the great fire. Although concrete shear walls were added as part of the retrofit, they are placed discretely and surgically in the structure, located away from historic finishes which have survived remarkably intact despite decades of neglect. Other unique components of the retrofit include: 1) center coring of the massive granite and masonry piers to promote rocking and reduce cracking and walking, 2) installation of corrugated sheet steel shear walls as a backup lateral system for a portion of the building, 3) fiber reinforced polymer strengthening of the concrete roof diaphragm and 4) pretensioned shear-friction load transfer mechanisms. This paper will discuss technical aspects of the retrofit scheme including computer modeling and use of provisions in the California Historic Building Code, but also will demonstrate how treating seismic safety and historic preservation with equal priority can enhance project outcomes.

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