A typical joint consists of steel beams connected to a steel haunch welded to an embedded plate placed at the outside face of the hall’s concrete wall. Direct steel-to-steel contact would transmit noise and vibration in the finished building and this needed to be avoided. To create the isolated joint, a neoprene bearing pad was added on top of the steel haunch on which the in- framing steel beam sat via a steel bearing plate atop the neoprene pad. To secure this connection, a pair of threaded studs welded to the haunch bolted down the beam. To avoid direct contact of the stud’s washer and nut to the in-framing beam, a neoprene washer was added between the beam and stud washer. But the problem was not fully re- solved, as the steel-on-steel contact could still occur between the studs and the beam and its bearing plate. To further eliminate noise transfer, a
The concert hall is the largest hall in the Hamel Music Center. The hall applies many creative, smart techniques to maximize the fine art of acoustics. Circles, better known as an acoustical coffer system, line the walls and ceiling to absorb and reflect sound. Two hidden, large (each capable of fitting 14 public transportation buses!) reverberation chambers flank either side of the stage. Curved balconies redirect sound back to the audience.
isolated from the large overall building (including the main lobby and its required support space) via the acoustical isolation joint. The two-inch acoustical joint assembly may be small but its impact is critical to the structure: It essentially separates the concert hall from the rest of the building framing into, and supported by, the 16-inch concrete walls surrounding and serving as part of the hall’s structural system.
neoprene bushing surrounded the weld stud. This resulted in a connec- tion design in which no steel touched and eliminated the possibility of reverberation. (However, these connections were permitted to transfer loads.) The structural design incorporated hundreds of these joints. Beyond this joint assembly, the concert hall’s perimeter concrete walls, soaring to a 70-foot maximum height, easily addressed lateral stability needs. The structure outside of the hall was attached to the hall’s walls via the acoustical isolation joint. This connection eliminated the need for unsightly and costly columns in the structural design. Instead, the column-free areas offer unobstructed views of concert performers. The recital and rehearsal halls utilized double-wall construction. For the recital hall, this consisted of an exterior precast wall panel in con- junction with an interior acoustically isolated concrete masonry unit wall. Similarly, the rehearsal hall’s perimeter used a precast panel but with an acoustically isolated interior drywall system instead. An acoustical coffer system (a series of strategically sized and strate- gically placed concave and partially or fully hollow circles) line the concert hall’s walls. These sizable circles treat sound by absorbing and reflecting it, along with the hidden reverberation chamber areas where sound actually passes through. The coffer system is visible and fits in beautifully with the rest of the hall’s aesthetics. Structural Design Enhances Building Aesthetics The Hamel Music Center’s second floor lobby hangs from the roof structure to create a column-free area at the main lobby and a floating lobby appearance, with a monumental staircase connecting the two levels. The lobby combines ductwork laterally into a curtain-wall sys-
An aerial view of the project: The largest area with circles in the concrete is the concert hall; both sides have large reverberation chambers for acoustic treatment. Adjacent to University Avenue in Madison, Wis., are the recital hall (left) and rehearsal hall (right).
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august 2020
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