In February 2003, a snowstorm sent the roof of Baltimore's B&O Railroad Museum Roundhouse crashing down, causing $30 million in damage. A stunned museum staff found the historic locomotives, exhibits, and rolling stock covered in heaps of snow, shingles, wood, and iron roof-framing members. Worse still, a sprinkler main was snapped in the collapse, completely flooding the exhibitions commemorating the "Birthplace of American Railroading," where the Baltimore & Ohio railroad was founded in 1827.
Baltimore-based firms Century Engineering, SMG Architects, and Whiting-Turner Contracting Company quickly got to work to replicate the historical roof and reinforce the building structure, while protecting the historic cargo contained in the oldest, most comprehensive railroad collection in the nation.
Because there were no extant drawings of the original 22-sided polygon roof structure and building, the Building Team had to examine and measure the recovered collapsed members and study the portion of the framing that had not been damaged to gather enough evidence to determine how the roof was originally constructed.
Due to the requirement for long wooden planks—in some cases 40 feet in length—conventional sawn timbers were deemed inadequate to support the new roof. Instead, glue-laminated wood products with a rough-sawn finish were chosen. Since it was impossible to replicate the original oddly formed, T-shaped truss girders , structural steel angles
A view of the interior looking up through the lantern.Photos: Century Engineering
conforming to ASTM A-36 were used.
The stability of the building was of great concern. Windows had to be removed in order to prevent the accumulation of wind loads e`ntering through the large opening in the roof. In order to restore lateral stability, 7,000 linear feet of half-inch-diameter steel cable were used to create a network of X-bracing between the interior columns.
As construction was about to begin, the crew discovered that it could not remove the remains of the lower roof all at once without compromising the building's stability. They had to sequence demolition in such a way as to maintain at least 85% of the lower roof diaphragm at all times while removing a mile of the temporary X-bracing cables.
The 60-foot turntable, originally built on the concrete slab-on-grade floor to transport rolling stock within the museum, had also been dam
The restored roundhouse, whose 22-sided roof was destroyed in a snowstorm. Photos: Century Engineering
aged, which made it impossible to move the 100-ton locomotives during construction. The team surrounded the stock with scaffold towers wrapped in ultraviolet-resistant mesh, which kept the stock ventilated but protected from sunlight.
The Building Team also determined that the rolling turntable could not support the weight of construction equipment. Whiting-Turner crews had to operate forklifts within a 20-foot circular ring of floor sandwiched between the turntable and the building columns.
The project was delivered on a design-build basis for under $10 million. "They figured out how to replicate the original roof structure with no engineering drawings, using new materials, and under difficult conditions,"said judge Bill Bast, SVP with structural engineer Thornton-Tomasetti.