USA - In mid-July 2003, Mice Creative awarded Total Structures the contract to fabricate the elliptical acoustic canopy which is flown under the new Hollywood Bowl structure in Los Angeles, California. The Bowl dates back to the late 1920s and several attempts have been made over the years to improve the acoustics so that members of the orchestra could hear each other. The last incarnation included the installation of 11 fibreglass spheres of various sizes under the direction of renowned architect, Frank Gehry.

The Design Architects for the new facility was Hodgetts + Fung Design Associates, with Gruen Associates acting as project architect for the main client and owner, Los Angeles County. The project, essentially comprised demolishing the existing Bowl and rebuilding from the ground up - the buildings on either side of the main roof structure to house new dressing rooms and production areas. The old bowl structure could fit inside the new Bowl with some 20ft to spare!

The new Bowl incorporates a radical acoustical approach developed by Chris Jaffe of Jaffe Holden Acoustics, Inc. Large panels hinge on the bottom chord of the cross-stage trusses and deflect the sound back down to the stage in a controlled way. The new acoustic canopy measures some 78ft by 68ft and is supported at a 10° angle below the main roof structure by inclined tubular steel struts. The principal components of the canopy are an elliptical perimeter ladder truss with integral catwalk, four cross-stage triangular trusses which support acoustic panels and three lighting battens.

The perimeter truss has curved 6" x 6" square aluminium chords with 3" x 3" diagonals and 6" x 3" vertical members, onto which ribbed plates are bolted to form the supports for a continuous open grid aluminium catwalk. These ribs are formed from aluminium plate that was water jet cut to the correct profile, and provide support for the curved fibre glass panels which cover the underside of the ellipse.

The side sections of the perimeter truss weigh about 3000 pounds and can be lowered to stage level (and removed on large custom-built carts) to allow conventional lighting grids to be rigged from the points provided on the steel arch trusses of the main roof structure. In contrast, the front and rear sections are permanently fixed to the main roof structure with large tubular steel struts.

Four large triangular trusses span across stage between elements of the perimeter truss and carry the main hinged acoustic panels. These panels are fabricated with aluminium ribs which support matte Makrolon panels on one side. They are a similar cross section to an aircraft wing and can be deployed at various angles using remote controlled linear actuators.

Three lighting battens are also provided. These are essentially large ladder trusses that span between sections of the perimeter truss. Again, the chords are 4" x 4" square aluminium with 2" diagonals with the galvanized steel lighting bar being supported from the bottom chord. The battens can also be raised above the perimeter ring truss and stored high into the main roof structure.

Theatre consultant for the project was Fischer Dachs Associates. The rigging and control system were designed and installed by Proskenion Design, LLC and LA Propoint, Inc. Total Structures worked closely throughout the design phase with Hopper Elmore and Associates who were the Engineer of Record for the canopy.

The project was completed in early June 2004 and was handed over to the client in time for the first show on 19 June and the Opening Night on 25 June. The new Hollywood Bowl is scheduled to be used for a number of high profile shows over the summer season including performances by the Los Angeles Philharmonic and other classical concerts as well as presentations of jazz, world music and special events such as Simon and Garfunkel, Eric Clapton, Sting, Rod Stewart, The Who and Norah Jones.

(Lee Baldock)


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