Location: California
Architectural Consultant | 2005
Client: Confidential
Cost: Confidential
Size: 100,000+ S.F.
With a multi-million dollar project at a standstill, the client came to us in need of a creative solution.
The client, who owns a large property in California with an old 100,000+ S.F. warehouse, had employed a well-known international architecture firm to create designs for converting the warehouse into a modern convention center. The City—hoping for increased tax revenues and beautification of the site—had agreed to grant a significant zoning variance if the client could break ground by a certain date.
Trying to promote sustainable practices such as adaptive reuse, the City also agreed to allow the building to retain its “grandfathered” rights—and to require only partial compliance with current building codes—if the client reused the building instead of building a new one. These are no significant concessions, and with millions of dollars of cost-saving implications our client was eager to take advantage of the opportunity.
But there was one problem which threatened the feasibility of the entire project and brought designs to a halt: the columns. Without removing the forest of closely-spaced columns in the original warehouse, it was impossible to create a 40,000 S.F. open auditorium—the central feature of the convention center. Our job was to find a way.
NOTE: Due to the confidential nature of the project and the interests of our client, we are unable to mention particular project details or show official architectural drawings and photos. Thank you for understanding.
Our primary task was to find a feasible, affordable solution for removing the 25 columns interrupting the auditorium space. We were also asked to consider affordable seismic retrofit solutions which would accommodate the architectural design of the new convention center.
Callifornia is well known for earthquakes, and for years has been anticipating a big one. Though the warehouse had survived small earthquakes for half a century without damage, building codes require significant safety upgrades when converting a building from a warehouse (with few people in it), to an assembly space (with thousands of people in it).
We were also asked to conduct market research to determine the profitability of a convention center versus other alternatives for the site’s redevelopment, such as converting the warehouse to housing or indoor parking.
Our market analysis yielded surprisingly positive results, so we focused our attention on removing columns.
There were several stipulations that added to the challenge. For one, the client requested that we not alter or damage the roof, which had recently been replaced. This limited our options.
Also, we quickly learned that all of the existing steel in the warehouse was coated with lead-based paint, meaning that before any new connections or welds could be made the steel would have to be sand-blasted: a slow and expensive process. With the client’s structural engineer showing a need for 140 tons of new steel to seismically retrofit the building—with 12,000 joints/connections—we were eager to find another alternative. Since some of the exterior walls contained asbestos, sand-blasting the steel there was not even an option since it stirred up the asbestos.
Furthermore, because of the change of use, increased occupancy, and additions to building codes over the half-century since the warehouse was built, major improvements to fire safety were necessary. For starters, all of the columns would need to be encased in concrete, which gave us even more incentive to remove the columns in order to save money and labor.
A major breakthrough came when we realized—by analyzing the original structural drawings with the help of mid-20th-century ASTM steel manuals—that the columns in the warehouse were five times larger than they needed to be to hold up the roof.
It turns out that the entire building has no diagonal bracing in its walls, or any shear walls for that matter. The closely spaced oversized columns—like a field of toothpicks—were the only thing holding up the building against lateral forces like wind and earthquakes. This meant that by resolving the lateral forces via other means, we could potentially remove some of the columns—provided we found another way to support the roof.Though we had canceled out ideas to support the roof from above with cable-stayed masts or suspension due to cost and damage to the roof, we found an opportunity to suspend the entire roof from the inside—without puncturing the roof. Because the warehouse was built with alternating ceiling heights (i.e., high bays and low bays), we discovered that we could suspend thin cables from the highest point of the columns in the high-bays and achieve enough of a slope to efficiently support all of the roof trusses within the auditorium from the perimeter—with only one row of (5) columns remaining in the auditorium space.
By adding concrete shear walls around the auditorium space and diagonal bracing in the exterior walls, we resolved all the lateral loads so that the columns were freed from all but gravity (roof) loads. Since we also had a solution for supporting the roof with cables, this meant that all but 5 of the 25 columns could be removed.
The two-step solution dealt with all three challenges: seismic retrofit, column removal, and fire safety. And it provided the best of both worlds: a concrete core for rigidity and fire resistance, and a tensile roof support system for flexibility. People used to believe that the best way to design a building for earthquakes was to make it stiff and unbreakable. It’s similar to how auto manufacturers used to think that heavy/indestructible metal cars protected human lives, until they realized that the best thing was for the car to be lighter and to crumble/absorb the impact that would otherwise be transferred to the passengers. Structural engineers and architects now realize that it’s better to design for flexibility: to allow a building to move with the earthquake instead of trying to resist it. A building needs rigidity to resist wind, but flexibility to resist earthquakes.
By creating the concrete shear wall around the entire auditorium, we also effectively divided the 100,000+ S.F. building into two smaller buildings as far as fire codes are concerned. This meant that the building now qualified for Type III construction (for smaller buildings, which are considered lower risk) instead of Type II (for large buildings and skyscrapers)—a significant cost savings.
During the course of our involvement we had regular meetings with the owner, the structural engineer (who was working only on seismic retrofit, not column removal), the contractor, and the project manager. However, as an independent consultant, we prepared all of our own designs and were responsible for conducting all necessary research, calculations, and computer modeling.
We would like to thank structural expert Goetz Schierle, PhD, FAIA, for his frequent advice and second opinions. Dr. Schierle teaches seismic design to architects at AIA conventions and has helped write the seismic design portion of modern international building codes.
This project presented quite a challenge, and we were involved in research, design, and development for four months.
Unfortunately, the project was canceled suddenly during our involvement due to serious funding shortages. It was later resumed under new management, with a diminished scope which did not necessitate column removal. Construction was completed in 2008 and the building is currently in use.