Riding it out
Like a Lexus,” is how engineers have described how the Hoag Hospital Sue & Bill Gross Women's Pavilion would perform when faced with a major seismic shock. It is the first structure of its type in California to use a moment-frame steel structure sitting atop tested and tuned base isolators to ride out earthquakes of up to 6.9 on the Richter scale—and this with the hospital located only 2 km away from a major earthquake fault. The moment frame, which uses 25- to 30-foot spans instead of traditional steel cross-bracing, opens up the structure to many new design possibilities, enabling it to offer the most modern of patient amenities. Recently architect Randy Regier of the Newport Beach, California, architectural firm TAYLOR and structural engineer Ed Gharibans of TMAD TAYLOR & GAINES explained the design, the all-inclusive planning process and the structural result in an interview with HEALTHCARE DESIGN Editor-in-Chief Richard L. Peck.
Randy Regier: The original building was built in 1952 as a one-story structure, and a patient tower was built in the 1970s. The Sue and Bill Gross Women's Pavilion was the most substantial in a series of additional development projects that have occurred over the decades. Our firm has been master planning the campus for more than 15 years and, besides having to design and construct new components, we had to comply with California's seismic upgrade requirements, as well. This resulted in a building that offers many innovations, from its basic structure to its interior design and layout.
Ed Gharibans: A basic building is a fixed structure atop a foundation. If the ground moves sideways, forces are transmitted to the building that bend connections back and forth until they break, as might happen with a spoon being bent back and forth. Base isolators are 20"-high rubber/steel plate “sandwiches” sitting on top of the foundation that filter out about 80% of this energy from the foundation/building connection. The building, like a ship sitting on waves, can move back and forth by as much as 30".
Regier: Movement of the isolators can be compared to the fanning out of a deck of cards—that's the basic movement involved.
Gharibans: The building moves with the isolator, with a moat around the building allowing for as much as 30" travel in any direction. As for the framing, conventional brace-framing creates rigidity with its columns and diagonal members. The moment frame is more open and flexible, giving a much smoother “ride” for the building in an earthquake. Elements of this moment frame/base isolator structure were tested for two years by the state to ensure seismic protection up to 6.9 on the Richter scale.
Regier: Without the cross-bracing diagonals and shear walls, the moment frame opens up the design so that you can provide patient rooms with full-width exposure to natural light and beautiful ocean views; wide, flexible corridors terminating at large windows; and increased natural light altogether.
Gharibans: Adding stability during a seismic event is the balanced design of the building, with a distance between center-of-mass and center-of-rigidity of less than 28" east-west and 5" north-south on a typical floor plan of 235′ × 150′. This counteracts building twist and rotation so that, even if the building may not look symmetrical, it behaves symmetrically in a seismic event. It's great to work with an architectural firm that listens to and understands engineering physics like this.
Regier: The steel moment frame and inboard toilets allow each room to have a large exterior window. There are also a convertible day bed, table and chair for families and visitors, and a nurse work area with hand-washing station. All the rooms are private—a standard at Hoag for many years—and are mirrored, rather than same-handed. This minimizes cost by not having to duplicate plumbing risers that occur with same-handed rooms.
The four-pod NICU is designed to admit plenty of natural light while still offering quiet and privacy.
Regier: The hospital features a hotel-like check-in as a central point in a series of “hubs” or gathering points that allow visitors to stop and orient themselves as they move along. A primary hub is at the outdoor compass rose, orienting visitors walking from the parking area to the building entrance. Other hubs are plazas, strategically placed benches, even a rockscape. Effective interior wayfinding is achieved by virtue of the open views allowed by the structure. Additionally, in keeping with the nautical theme of much of the interior design, nursing stations are marked by teak “lanterns,” providing visitors with an identifiable beacon.
Regier: The exterior features excellent sculptures by California sculptor Tom Van Sant, one of which is a 65'-long, cast-in-place concrete intaglio showing sandpipers, shorebirds, and wave forms. Also, marking the parking structure is a sculptural wall featuring dolphins. All of this complements the shorefront location of this facility.
Regier: To allow for long-term ease of maintenance and infection control cleaning, we established specific zones for the MEP systems. Using the corridor as the basis, we divided the building into quadrants so that if parts of the building need to be shut down, they only need to shut down specific quadrants at a time for maintenance, not the entire building. We built in easy access to HVAC control valves, gas piping, and plumbing—even ductwork—so that systems can be turned on and off and cleaned without undue difficulty.
Regier: It's so important to have a working team—the owner, the architect, the engineers, the contractor and all the subs—who truly put the project ahead of themselves and their personal interests, and work to come to common solutions. Because of this, we were able to come in two months ahead of schedule and under budget.
The other lesson is that if I were to do this again, I would plan for commissioning during the project, rather than at the end, so that all systems engineers would have a feeling of ownership throughout. We were always able to work things out, but commissioning systems along the way would have expedited the process.
Gharibans: I would echo Randy's comment that teamwork in a project this large and unique is crucial. The result is a project that is one of a kind. HD