Restoration - Project of the Year

B&O Railroad Museum Roundhouse
Baltimore, Md.

Restoring the historic B&O Railroad Museum roundhouse in Baltimore, Md., would have been difficult under any circumstances, but the structural damage caused by a sudden roof collapse presented Century Engineering and the entire restoration team with an unprecedented challenge.

Half of the roundhouse's low roof - approximately 19,000 sq. ft. - collapsed after the President's Day snowstorm in February 2003. Thousands of pounds of snow, slate shingles and wood and iron roofing members were piled on top of the historic rolling stock, locomotives and other museum exhibits.

The domed upper roof and half of the low roof remained intact, but their stability was questionable. The brackets supporting the girder trusses broke, which left the columns intact but unbraced at the low roof level. Falling debris damaged several I-beams and some of the X-bracing between the columns.

The collapsing structure snapped a 3-in.-diameter natural gas line and a 6-in.-diameter sprinkler main. Water filled a turntable pit below and flooded the museum. Additional water from melting snow and heavy rain that followed the storm added to the flooding problem, which compromised the bearings of the turntable's pivot mechanism and saturated its decking and timber framing.

Severed electrical conduits suspended from the roof exposed the flooded museum to electrical current.

"It was like starting over after a bomb had gone off," said one judge. "There were huge construction issues with this project that made it a real challenge for the team."

Engineers faced a number of obstacles, both immediate and long-term. Unlike a typical project, this one started with immediate and urgent concerns of public safety, building stability and protection of museum artifacts. Working closely with the owner and contractor, Century Engineering, which has an office in Towson, Md., quickly evaluated the remaining structure and produced designs for the multiple types of building stabilization needed. The contractor, Whiting-Turner Contracting of Baltimore, Md., was able to start work within a couple days of the collapse.

Once efforts began to stabilize the structure and remove debris, engineers' focus shifted to the design of the replacement roof. The task was complicated by the century-old museum's National Landmark status. The building's aesthetics would have to remain unchanged, while substantial structural upgrades would be required to stabilize the building and prevent future failures.

The original design elements that contributed to the collapse were eliminated, while historic design elements no longer in use today were mimicked.

While the domed upper roof was still intact, questions remained about its condition. Once the design for the low roof was complete and construction had started, engineers inspected and evaluated the upper roof. When it was evident that it was in poor shape, many courses of action were considered, including reinforcing members and building a secondary roof above the existing roof.

The museum decided to replace the roof, which presented the unique challenge of phasing the work with the ongoing reconstruction of the lower roof. Careful sequencing of work by the contractor resulted in a safe and efficient process and allowed the museum to reopen in just 20 months.

The museum's landmark status complicated the design of the roof structure. The roof would have to look the same as the original roof built in 1884, but with considerably more capacity.

Further complicating matters, no engineering drawings existed for the building, and the large amount of debris at the site prohibited the use of manlifts that would have given designers a closer look at the roof. Before the debris was cleared, engineers examined the remaining structure with binoculars, closely measuring and examining collapsed members.

Consultations with museum staff, architects and Maryland Historical Society members resulted in a roof that is difficult to distinguish from the original but with substantially more capacity.

Preengineered wood replaces sawn lumber, A992 steel is used instead of wrought iron, and revised web spacing on the main frame members contribute to the new design.

The unconventional jobsite tested contractors as well. Because a number of museum exhibits could not be removed from the roundhouse during the demolition and construction process, they had to be protected. Many locomotives and other rolling stock were wrapped with ultraviolet-resisting fabric and enclosed in plywood boxes with scaffolding-supporting plywood floors.

The limited capacity turntable in the center of the roundhouse would not support the weight of most construction machinery, so contractors had to stage manlifts, forklifts and other equipment on a 20-ft. circular strip between the roundhouse's columns and the turntable.

To reconstruct the upper roof, which was located immediately above the turntable, crews had to remove the turntable's deck, exposing two large steel girders with timber outriggers at approximately 30 in. on center. Since the framing was not strong enough to support scaffolding that would in turn support the dome roof, crews crafted a complicated system of scaffolding that was meticulously threaded around the turntable framing.

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