Los Angeles Natural History Museum Gets Major Makeover
In 1913 the Natural History Museum of Los Angeles County opened the doors to its now-iconic Beaux Arts main building. One hundred years later, the museum is about to unveil the latest part of a seven-year, $173-million physical transformation—one that preserves the past, fortifies its existing structures and creates new spaces.
The museum's exhibits are dedicated to preserving the past, but the team that designed and constructed the museum's original 1913 facility didn't follow such exacting standards when it came to creating as-built drawings. During the planning phase of the recent seismic upgrade and renovation project, which broke ground in 2006, the team had a mere 24 pages of as-built drawings available for the 1913 structure, says Don Webb, president of Cordell Corp., the project's construction manager.
"A new building project is mainly about planning, but the restoration of a historical facility like this 100-year-old museum is about problem-solving—because so much of what you get into is not only unknown but unknowable," Webb says.
From the start, the potential cost of the "unknowns" made the full scope of the program difficult to gauge. Webb notes that the amount of funds available for later phases of work hinged on keeping the historic restoration's costs under control.
He says the team was careful not to presume that more study, analysis and investigation would yield the best decisions. "Often, just getting started with imperfect information provides the key—both in terms of the quality of decision-making as well as the ability to generate funding," he says. "We knew that if we put together enough of a project and got it started and showed success, then future phases would emerge."
The effort paid off. During the past three years, the public has seen the renovation of the 1913 building and the unveiling of other program elements. In total, the seven-year effort includes 108,000 sq ft of renovated and reinstalled indoor spaces. On the museum's North Campus, construction is under way for the new $13-million glass-walled Otis Booth Pavilion. The pavilion was designed by CO Architects, Los Angeles. Other additions on the North Campus include 3.5 acres of gardens, a new parking structure and a café.
The project team included general contractor MATT Construction, Santa Fe Springs; landscape architect Mia Lehrer + Associates, Los Angeles; Cordell, which has main offices in Los Angeles and Sacramento; and CO Architects. Key subconsultants included structural engineer John A. Martin & Associates, Los Angeles, and MEP engineer IBE Consulting Engineers, Sherman Oaks.
From the start of the program, the team faced considerable challenges in renovating and retrofitting the 1913 building—designed by Frank Hudson and William A.D. Munsell—and the neighboring 1920s building. Jackie Vinkler, a principal with John A. Martin, says, "The 1913 building, which started off the whole project, is a historic structure made of unreinforced masonry, and the intent was to get it back to its glorified days."
To achieve that goal, the team had to devise a way to give the three-level building a seismic upgrade without altering its classic features, including columns, cornices, arches, domes and especially its 58-ft-tall, 75-ft-dia rotunda, which is topped by a spectacular 20-ft-dia stained-glass skylight.
The team also wanted to avoid an expensive relocation of the museum's massive basement collections. The cost of such a move would have equaled 25% of the project's total available budget, says Jorge de la Cal, a CO Architects principal and project director.
He says that most traditional methods of seismically upgrading a building—such as adding shear walls or braced frames to existing walls—"would have affected the space available for the collections and necessitated, at minimum, a relocation of large portions of the collections."
Core Concept
The solution was dry center coring, a technique that Jim Muenzer, MATT Construction project executive, says was previously unheard of for a structure of the museum building's size and historic significance.
Muenzer says, "We found only one company in all of the U.S. that was qualified to do that type of work, so at the time it was an innovative technology that not a lot of people developed, but it turned out very successful." That company was RDC Construction Services Inc., a California-based specialist in center coring.
On the museum project, a drilling rig was placed on top of the 63,695-sq-ft building and 6-in.-dia shafts were drilled down through the walls to the foundations, at 7- to 8-ft intervals. A total of 122 shafts, ranging from 40 to 60 ft deep, were drilled through the 2-ft-thick walls without hitting any windows, beams or decorative marble tile.
CO Architects' de la Cal says, "Although we uncovered some historic drawings, photos and documents from the museum's archives, there were no real working drawings from the original Hudson & Munsell design." He adds, "We had to do a very sensitive investigation to make sure the installation of vertical cores from roof to foundations kept the historic structure intact."
Drew Wesling, MATT project manager, says there also was concern that the rebar might rupture the brick walls, but he notes that the steel drill bit that was used had enough rigidity and precision to cut through them successfully.
Once the holes were drilled, rebar was threaded down into the foundations and the shafts were filled with polymer resin grout. The tops of the rebar were then tied together with a concrete connector bond beam just below the roof level.
To create a stronger diaphragm, the 3-in.-thick concrete roof slabs were shaved and then carbon fiber wrap was laminated to the slabs so loads could be transferred from the diaphragm down to the bond beam, the center cores and into the foundations.
When that process was completed, the team focused on separating the 1913 building from the adjacent 1920s structure, which had been joined at the foundations.
"We had to use a concrete saw to saw the sides, roof and floor lines of the buildings," says Wesling. "And in some cases we couldn't get the saw in, so we had to use rotary hammers to chip away a 4-inch gap and then put in expansion joints along the perimeter walls, roof and doorways between buildings."
After the 1920s building became a stand-alone structure, shear walls were installed on the north-south axis for support and a glass-enclosed elevator was added. The east-west concrete wall was replaced with a series of curtain walls, which improved the lateral system and allowed the architect to bring in more natural light.
In its grand reopening, the museum plans to highlight the new Otis Booth Pavilion, a 62-ft-tall by 64-ft-wide glass box structure, which will house a hanging 63-ft-long whale skeleton.
"The all-glass structure exhibits design and engineering prowess in its structurally glazed curtain wall construction with vertical suspension rods and horizontal knife plates," says de la Cal. "The frameless structure and glass size are determined for minimal visual impact on the exhibition designs."
He also says that the glass on the building's east-west sides will have a ceramic frit pattern to mitigate solar heat gain.
In addition, a radiant slab at ground level will conduct heating and cooling. The pavilion's ceiling and rear wall will become a continuous full-color LED display, which will allow for vibrant light shows.
