100 Van Ness Avenue: A Unique Tower Crane SupportNov 12 2013 · 0 comments · NISHKIAN MENNINGER, Residential ·0
San Francisco, CA – The existing 29 story office building in the San Francisco Civic Center neighborhood is currently undergoing significant renovation as the occupancy changes from office space to residential use. 100 Van Ness Avenue, constructed in 1972, stands at 415 feet tall and used to be clad with precast concrete panels. NREA Development Services, Emerald Fund, with Solomon Cordwell Buenz Architects, Nishkian Menninger, and Plant Construction have developed plans to convert this office building into a total of 399 residential and retail units, totaling over 400,000 square feet of livable space. The precast concrete panels are being replaced with a modern glass façade, and the entire interior has been removed to be rebuilt with high-end finishes. While demolition and construction is already underway, a normally overlooked but critical element of this renovation required careful planning and design.
In new construction, a tower crane may be placed in the site, atop a large, deep foundation. However, at existing buildings, site conditions do not always allow for placement of these large foundations. The existing site at the corner of Van Ness Avenue and Fell Street left little room for a conventional tower crane foundation. A main street to the south, a historical building to the east, a mid-rise to the north, and Van Ness Avenue (Highway 101) to the west, all blocked the placement for a standard tower crane foundation.
After much deliberation, plans were drawn up to cantilever the tower crane up above Fell Street and the sidewalk. By raising the crane above the required height limit for trucks and pedestrians, the tower crane could be used at any time of day, without blocking traffic or pedestrian access.
The tower crane support looks simple in its overall design, but in reality, significant detailing was required for construction. Four steel columns rise up from the basement, through the ground floor and sidewalk on Fell Street in order to support the two large cantilevering steel beams. Steel tube bracing was added at each level and between the two support beams to add lateral/seismic stability.
For constructability reasons, the existing columns and the new crane columns needed to be offset from one another. This offset allowed for the columns to rise up through a floor without removing any existing beams. Special detailing was required in order to bridge the gap between the new and old columns at the first garage level. The design allows the crane support column loads to be transferred to the existing columns at this garage level, reducing the amount of additional steel for the crane support.
With the crane in place, the work has progressed quickly; almost all of the concrete panels have been removed. Soon the new glass façade will start going up and the new residential partition walls and finishes will be installed. The conversion of this old office tower would not have been possible without the tower crane and its unique cantilever support.
To view series of pictures from the de-construction process at 100 Van Ness, visit Tumblr at http://100vanness.tumblr.com/