Fleet Center Boston, MA
Architect: Ellerbe Becket Inc., Kansas City, MO
Project Location - Accessibility dictated urban location near transportation center. Constraints included existing Boston Garden, future Central Artery, MBTA 5-level parking garage with relocated Green Line and new MBTA commuter rail platform with thousands of passengers each day.
The 3-dimensional physical constraints were further complicated by the fourth dimension--time. Each planned project has a schedule tied to funding, design and construction with interdependent sequences which must be carefully coordinated.
Structural Design - The new facility's structural frame had to satisfy an array of loading conditions posed by the planned activities within, and the every-changing environmental forces of the New England weather. The Arena floor framing must be level and rigid enough for the changeable ice rink and also accommodate removable floor systems which will support wrestling rings or circus elephants. The "bowl" framing must safely support the thousands of fans in their seats whether sitting quietly at a graduation ceremony or swaying rhythmically to a rock bank, without columns obstructing their views.
The roof must support suspended scoreboard, lights, catwalks, show-rigging and, of course, championship banners, while resisting the 2000 tons of snow which could fall on the 3-acre roof.
Each of these tasks must be achieved while maintaining a framing system which will "deliver" the arena loadings to the supporting garage without overstressing the completed construction. The resulting arena's structural design is composed of a lightweight steel frame supporting poured-in-place concrete slabs supported by corrugated metal decking which spans from steel beam to steel beam. The use of steel beams made composite with the deck supported concrete slabs by welding headed studs to their flanges allows the use of shallow members which helps to minimize the floor-to-floor heights in the completed building and thereby preserves the "sight-lines" from the seats to the arena floor.
Large steel trusses are used to span the 300 feet from front to back wall leaving the seating area column-free. Built-up steel plate girders are used to transfer the Arena loads from the Arena radial grid to the underground garage orthogonal grid.
Because of the constrained site, the steel erector assembling the frame constructed all the pieces to the Arena floor along with a truck ramp leading to that level. Then the erector's cranes drove up the ramp to the Arena floor to complete the remainder of the bowl and roof frame. The long span roof trusses were assembled on the floor and lifted into place by two cranes working in unison. Meanwhile the thousands of North Station daily commuters and Boston Garden event-goers continued below unimpeded.
As with most of today's technology, the design and construction of the new Arena structure made use of state-of-the-art computers and software. The building loads were catalogued by the structural engineer's analysis and design programs. A scale model of the Arena was tested in a wind tunnel where a computer simulates 100 years of weather in a few minutes while recording the peak wind and snow forces which should be expected. The steel fabricator uses automated detailing to insure consistent fabrication and fitting together of pieces in the field. And the General Contractor responsible for coordinating all the various trades working at the site uses special scheduling programs to monitor the progress.
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