Should San Francisco Get Taller?

Some San Franciscans don’t want a new cluster of skyscrapers. Robert Selna and John King describe the heated controversy that engulfs the city’s plans for its heart. Architects, developers, and people who already live downtown come out in droves, for public meetings. There could be as many as seven (another source says 13) new towers amid the skyline, and some of them could be as high as 800 feet, or about one-third again as tall as the 550-foot limit presently dictates. And then there’s the Transbay tower, a proposed 1,200-foot behemoth. The complete plan is at the San Francisco Planning Department’s website.

One of the goals, say Selna and King, is to make the city center more amenable to mass transit:

The rebuilt transit center is scheduled to open for bus service in 2014. The overall budget for that phase of the project is $1.2 billion, $411 million of which is expected from land sales….The second phase, in theory, brings Caltrans commuter service and a high-speed rail line to the terminal by 2018….Tax revenue from the new buildings would help pay for part of the multibillion-dollar transit hub intended to serve bus passengers from around the Bay Area and rail commuters from the Peninsula and farther south.

Some say even transportation is a minor consideration compared to the projected demand for office space. Howard and Mission are the two streets most affected, though the plan includes an area bounded by Market, Main, Clementina and New Montgomery Streets. Even in a best-case scenario (best, that is, for those who want more skyscrapers) the first breaking of ground could not occur before 2010, and a lot could happen before then.

One argument for a general height increase is a desire to reconfigure the skyline of downtown San Francisco, which some consider monotonous. But developers have still been able to situate tall buildings in other parts of the city, such as the 641-foot One Rincon Hill South Tower (see photo – it’s the shiny one). A good argument could also be made, that how a city looks from the air is the least important thing about it.

Historic preservation has to be considered, along with a reduction in vehicle traffic and an increase in space for pedestrians. As for the height increase, some people simply feel that enough is enough. Discussing an important issue, the shadows that would fall on public parks, an issue which supposedly had already been settled by law back in 1984, Selna and King say:

While studies are still being done on what shadows would occur at different times of the year in different locations, the likely loss of sunlight prompted planners to pull heights down from what some developers had sought – though some new shadows would be unavoidable.

Question: given the current state of modeling software, why does it take so long to figure out where shadows would fall?

SOURCE: ” A NEW SKYLINE ON S.F. HORIZON ” 05/01/08
photo courtesy of fredsharples , used under this Creative Commons license

AGS Case Study: Restoring 215 Fremont Street, San Francisco, California

The venerable L-shaped industrial building had been around since 1927, and had suffered badly in the 1989 Loma Prieta earthquake, and then stood empty for a decade. Its rebirth is described in “Renovated Office Building at 215 Fremont Street, San Francisco California,” one of the case studies detailed in Architectural Graphic Standards, 11th Edition, from the American Institute of Architects, published by WILEY. The piece was written by four of the participants: James Kellogg, AIA, HOK; Lynn Filar, HOK; and Navinchandra R. Amin, SE and Vivian L. K. Wan, PE, both of Middlebrook + Louie.

The team that took on the revival of 215 Fremont faced real challenges. A large part of the project consisted of figuring out just what they were dealing with, hindered by the fact that many of the original drawings were either missing or indecipherable. When the nitty-gritty evaluation phase started, some unpleasant facts turned up. For example:

Since the original construction, the building had experienced differential settlements of up to 5 inches. Core samples and dynamic load tests of the existing floor slabs provided data necessary to evaluate the viability of components of the existing structure…

A large part of the evaluation process consisted of cranking up ETABS and SAP 2000, respected CAD programs that together gave a picture of how nicely the building would work and play with gravity and seismic loading. The prognosis wasn’t good. For starters, an earthquake would turn the ground beneath 215 Fremont into soup. How would they get this thing to stay up? Equally important was the need to satisfy ever-evolving building codes. We’ll let them tell it:

A new structural system needed to be developed for the project that would be sufficiently stiff to alleviate the induced internal forces in the existing floor slabs and punched exterior walls. Additionally, the structural system needed to use the full length and width of the structure to minimize the seismic overturning forces applied to the foundation…

As often happens, necessity gave birth to invention, and an elegant, innovative solution was arrived at.

This retrofit of an early twentieth century building led to the creation of a unique connection between steel braces and concrete columns, as a combination structural system comprised of steel-brace, frame-and-concrete shear walls was developed to meet all critical requirements.

The article explains exactly, and in great detail, how the team did it. And that’s not all. Every bit of 215 Fremont was remade into a paragon of sustainability and a fully compliant respecter of seismic requirements. What had once been basement storage space was now a much-needed parking facility. From bottom to top, from the new pedestrian-friendly retail arcade to the attractive rooftop terraces, the whole edifice was transformed. Impressed, the Structural Engineers Association of California gave the building its coveted Excellence in Structural Engineering Award.

215 Fremont, later also known as the Charles Schwab building and the Emporis building, was a showpiece as its neighborhood morphed into the happening “multimedia gulch.” When the project was finished in early 2001, a major corporation immediately occupied the entire building. The renovators had successfully made a statement: the cultural tone of the whole area had been elevated.

But any project of this kind also raises disturbing questions about the ultimate futility, in the event of catastrophic emergency, of even the strictest building codes.

SOURCE: “Renovated Office Building at 215 Fremont Street, San Francisco California” 2007
Photo courtesy of WILEY by Michael O’Callahan