Feb04

Historic San Diego Building Gets a High-Tech Makeover

Built in 1914, the registered-historic Hotel Churchill was constructed as the City of San Diego prepared to host a large influx of tourists from around the world for the Panama-California Exposition of 1915. Over the subsequent century of use by a variety of different owners it was even converted into a medieval-themed hotel. The aging building got a chance at new life when it was acquired by the San Diego Housing Commission with the intent to renovate it to provide sorely needed affordable housing to the downtown San Diego community.

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Hotel Churchill Circa 1930 Hotel Churchill 2014

When KPFF was brought onboard to support the extensive renovation and rehabilitation design proposed by Studio E Architects the first order of business was a comprehensive evaluation of the building’s structural deficiencies. The 7-story building, a combination of concrete shearwalls and unreinforced masonry infilled concrete frames, had problems common for a building of this vintage: a weak/soft story at the tall 1st floor through which none of the concrete shearwalls from above extended, and under-reinforced, non-ductile concrete columns also at that level. KPFF’s recommendation to the project team was that a voluntary seismic upgrade be performed to reduce the possibility of 1st story collapse in a large earthquake despite no code-mandated retrofit having been triggered.

KPFF looked at a variety of conventional retrofit schemes including new concrete shearwalls or braced frames but these schemes were going to be very expensive and invasive, would ultimately compromise the architectural programming and historic aesthetic of the building, and the inclusion of these systems at the 1st floor could have the unintended consequence of dramatically increasing the building’s overall stiffness and therefore attract much higher seismic forces at the upper levels of the building. This unique combination of conditions was perfectly suited for a retrofit using fluid-viscous dampers. Fluid-viscous dampers essentially act in the same fashion as hydraulic shock absorbers on a car’s suspension system, dissipating seismic energy in the building by forcing fluid/oil through small orifices in the damper’s cylinder. 

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Typical Dampers

These dampers in combination with new steel infill moment frames at the 1st floor provide a means to control seismic displacements in the 1st floor concrete columns without increasing seismic accelerations in the floors above or creating excessively high seismic shear and overturning on the new shearwalls and foundations that were installed in the basement of the building. The damper retrofit was performed in combination with Fiber-Reinforced Polymer strengthening of existing 2nd and 1st floor diaphragms and confinement wrap of unconfined columns. Being the first damper retrofit of an historic building in San Diego KPFF worked closely with the City of San Diego’s Department of Development Services and the third-party peer review panel to ensure a comprehensive review of the analysis and design in a very expeditious fashion, with the entire peer review process completely in just 3 months’ time.

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   Damper Installation

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   FRP Installation

The project is currently about 80% complete in construction, scheduled to be finished in May 2016.

                                                                                                                       

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