Designing for Multiple Disasters
Earthquakes, hurricanes, floods, oh my! Designers of hospitals and other medical facilities often must accommodate one, sometimes two, of these disasters into their designs. But all three?
No designer had ever faced that hurdle until NBBJ designed a new $190 million hospital in Charleston, South Carolina for the Medical University of South Carolina (MUSC; figure 1). This feat was accomplished under some of the nation's most stringent building codes for making disaster-resistant hospitals. Satisfying those requirements while designing a facility that met the client's aesthetic and operational needs was just NBBJ's first challenge: The design also had to win approval from Charleston's Board of Architectural Review.
An innovative design makes the Medical University of South Carolina's new Ashley River Tower resistant to flooding, hurricanes, and earthquakes
Speed of design and construction was essential, too, because MUSC's existing hospital (still operating) was at near-maximum capacity. The design process began in February 2003. By April 2003 the initial building design in the schematic design phase was completed.
The 641,000-square-foot hospital, which opened in February 2008, is called Ashley River Tower. Located on the MUSC campus, the hospital is the first project in a 20-year master plan designed to rebuild the campus. MUSC wanted a much-needed facility that incorporates the latest technology, provides future flexibility and offers a comfortable, healing environment.
NBBJ's New York and Columbus offices partnered on the project. Designers from the two offices worked closely with MUSC, as well as with the South Carolina-based design firm LS3P and other professionals, to ensure that the design created would meet both the applicable building codes and MUSC's operational goals. For example, a decision had to be made whether to construct a freestanding energy plant or one located in the hospital. The freestanding option was chosen based on several factors, including zoning restrictions on building size, possible need for plant expansion in the future, and the cost and method of connecting a plant to the hospital.
Ashley River Tower has three components: a seven-story tower that contains 156 spacious private rooms; a four-story diagnostic and treatment center housing surgery, imaging, and interventional cardiology; and a conservatory garden that doubles as the hospital's lobby and serves as a center core between the tower and diagnostic and treatment center.
Designing for disaster
Designers of a hospital often must accommodate in their design a building code's disaster-resistant requirements. These can be stringent. Two notable examples are California's seismic requirements and Miami-Dade County (Florida) provisions for hurricanes and flooding. When it comes to designing a disaster-resistant hospital, however, Charleston is in a league of its own. The city is one of the few places in the world where the potential exists for three disasters: Earthquakes, hurricanes, and flooding.
Take earthquakes. One of the largest ever in the Southeastern United States occurred in Charleston in 1886. What makes the city vulnerable to earthquakes are underground faults formed millions of years ago. Compounding Charleston's seismic problems is its soil. The site chosen by MUSC is located above reclaimed marshland covered by fill material; during a seismic event, this type of soil becomes unstable and can't be depended upon to support a substantial structure like Ashley River Tower. In addition, the soil at the hospital's site settles at a rate of approximately a half inch per year.
As for flooding, Charleston is located on a peninsula where the Ashley and Cooper Rivers join and flow to the Atlantic Ocean. Ashley River Tower is only 1,500 feet from the Ashley River, and just six to seven feet above sea level. Consequently it is susceptible to flooding during heavy rains, storm surges, and unusually high tides. In 1989 Hurricane Hugo battered Charleston with 135 mph winds and a five-foot tidal surge.
Around the same time NBBJ began the design process, South Carolina adopted the 2000 edition of the International Building Code, which classifies Charleston as a zone of high seismic activity. The classification puts the city on a par with coastal California's seismic requirements. Additionally, Charleston has stiff requirements for making a hospital hurricane- and flood-resistant. Plus, under the city's building codes, Ashley River Tower must be able to continue operating during a disaster.
Faced with so many tough requirements, MUSC had given serious thought to locating the new hospital off campus. But MUSC ultimately decided it was committed to the local community and to its campus, which opened in 1955.
As a first step in the design process, NBBJ identified each disaster type's requirements, including the wind load and lateral forces characteristic of the project's geographic location. Next, NBBJ collected key data, such as requirements for wind speed resistance, lateral forces resistance during earthquake, and elevation above sea level for flood protection. Using this data, NBBJ developed building design options that accommodated multiple criteria and incorporated design features consistent with the client's budget, operation program, and aesthetic goals.
To confirm that the new hospital would withstand both hurricane-force winds and a major earthquake, NBBJ designed a 20' × 15' mock-up portion of the aluminum frame and glass curtainwall (figure 2). The mock-up was put under rigorous testing by a Florida laboratory, including testing for hurricane winds in excess of 130 mph and for major earthquake conditions; this testing included window and curtainwall frame racking to confirm that the glass remains in place when the forces simulating the disaster are applied. NBBJ's design for the exterior specified materials that make the glass from ground level to 30 feet resistant to large missile impacts, and from 30 to 60 feet to withstand small flying debris in a hurricane. The exterior glass throughout the building consisted of two separate layers, with the outer layer consisting of laminated glass sandwiched with a plastic interlayer. The design held the glass in the frame despite breaking or shattering of the outer layer.
Mock-ups of the expansive steel and glass structure were developed and rigorously tested to ensure Ashley River Tower could withstand hurricane-force winds and flying debris
During a seismic event, buildings can sway several inches. To allow for this, NBBJ provided for seismic joints between the hospital tower and the diagnostic and treatment center. These joints allow the building to move as far as 16 inches—eight inches inward or outward. Because of the seismic joints, gaps run through the floors, roofs, and walls of the hospital. The gaps, depending on location, are covered either with sliding metal plates or rubber.
The curtainwall framing of the sail, a special feature of the exterior (see below), is also a unitized system, allowing the large glass panels of the exterior to move somewhat independent of one another.
To keep the hospital operating during a disaster, NBBJ needed to protect critical air and energy supplies. This was accomplished by designing coiled pipes and wires where these services cross the seismic joints. Like flexible straws used for cold drinks, these pipes and wires move easily back and forth during a seismic event. The firm worked closely with a special seismic consultant and structural engineer, and the mechanical equipment contractors employed special consultants to engineer and supply the materials to anchor and brace equipment to prevent damaging movement during a typical earthquake.
To protect the hospital against flooding, NBBJ used high-strength steel and concrete stilts that put the first floor 10 feet above ground level (figure 3). Above that first floor, NBBJ located generators, pumps, and other critical equipment that code says must be protected from flood waters. At this level, NBBJ also designed the hospital's vehicular and pedestrian entrance, reached by a ramped drive and stepped walkways.
The facility's first level is elevated to assure medical services are not disrupted in the event of heavy flooding
The ground level is reserved primarily for parking. No life safety equipment is housed at that level. But some features, such as elevator lobbies and storage rooms, had to be located there, and many are protected by special flood gates and doors. Built-in basement pumps can pump out floodwater once it begins receding.
NBBJ's disaster-resistant design also included a 90,000-gallon water tank, located in the lowest (garage) level of the hospital and occupying a 30' × 38' × 10' reinforced concrete vault, with a fire pump sitting above it on the hospital's first floor. This water is available for the fire protection system if Charleston's water supply is temporarily interrupted.
Ironically, one of NBBJ's biggest challenges didn't involve disasters, but rather obtaining design approval from Charleston's conservative and historic-focused Board of Architectural Review. To win board approval for a design of a modern hospital for the 21st century, NBBJ created a link to the city's past by including classic features such as brick masonry facades, punched window openings and a limestone colonnade. To reflect Charleston's nautical heritage, NBBJ designed the south face of the patient tower to mimic a billowing sail.
Designing a disaster-resistant hospital under tough code requirements isn't easy when multiple disaster types are involved. Close collaboration with the client throughout the entire design process is essential. So is integrating into the process from the outset the expertise of engineers and other professionals in several disciplines, particularly to enhance everyone's understanding of the technical code requirements for making a facility disaster-resistant three times over. These steps won't prevent a disaster, but they reassure both the designer and the client that the facility, as designed, will not only meet the functionality required and expected by the community if a disaster occurs, but also will continue to deliver the postdisaster relief urgently needed by the client. HD
For more information, visit http://www.nbbj.com.