SCOPE
Provide new bleachers as designed by Northwest Industries, Inc. consisting of 1 such unit(s), rows high (X) in overall length, with the accessories and features defined below. Net seating capacity of (XXX) (not including aisles, based on 18″ per seat).
UNDERSTRUCTURE
The understructure of each unit shall consist of a series of frames. Standard dimensions are 8″ rise per row, 17″ height of seats above foot plank and 24″ depth of row. Frames shall be aluminum angle, 6061-T6 alloy (or mechanically equivalent). Each frame shall be unit-welded using the metal inert gas method by qualified welders under guidelines established by the American Welding Society. Each frame shall consist of vertical, horizontal and diagonal bracing to support the seat and foot planks as specified herein. Bolted or otherwise mechanical fastening of each frame’s components will not be acceptable. All cross bracing and horizontal bracing is to be aluminum angle 6061-T6 (or mechanically equivalent) and placed in number and location to sustain design loads.
SEAT PLANK
Shall be aluminum,nominally 2′ x 10″ with a wall thickness nominally .076″. All seat plank shall be aluminum alloy 6063-T6 and have clear anodic coating (204R1) applied in accordance with AAS Standard AA-M10C22A31.
FOOT PLANK
Shall be aluminum, non-skid surface nominally 2′ x 10′, footrest shall consist of 2 such planks with a wall thickness nominally .078″. All foot planks shall be of aluminum alloy 6063-T6 and be mill finish.
VERTICAL RISERS
Vertical riser planks shall be provided between seat and foot plank. Plank shall be (2) 1″ x 6″ at top row and 1″ x 6″ on all other rows with a wall thickness nominally .078″. All riser planks shall be of aluminum alloy 6063-T6 and be mill finish. End caps shall be field installed using mechanical fasteners on all vertical risers.
AISLES
Aisles footboards shall be of all-aluminum. Two aisle stiffener angles shall be used to strengthen the aisle step. Aisles shall be 54″ wide located as required by the applicable codes defined above.
AISLE HANDRAILS
Where there is seating on both sides of the aisle, handrails located with the aisle shall be discontinuous with gaps or breaks at intervals not exceeding 5 rows to facilitate access to seating and permit crossing from one side of the aisle to the other. These gaps or breaks shall have a clear width of at least 22 inches and not greater than 36 inches, measured horizontally. Where handrails are provided in the middle of aisle stairs there shall be an intermediate handrail located approximately 12 inches below the main handrail. The handrail shall also have rounded terminations, bends or fittings.
GUARDRAILING
The railing shell consists of upright members of mill finish extruded aluminum angle. Horizontal members shall be of extruded anodized aluminum tube 1-5/8″ O.D. with a wall thickness of not less than .140″ (schedule 40 pipe). Rail pipe shall attach to upright members by means of heavy duty tension bands using 3/8″ diameter carriage bolts, lock washers and nuts with hot dipped galvanized finish and consist of internal splice connectors, elbows and pipe caps mechanically fastened. The guard railing system shall be a chain link system consisting of three side rails and two back rails with a top rail height of 42″ mesh galvanized chain link fabric, tension bars, brace bands, combo rail end caps and wire ties.
ENDCAPS
Endcaps shall be extruded aluminum 6063-T6 alloy, and have a clear anodic coating (240R1) applied in accordance with AAS standards AA-M10C22A31. All endcaps are anodized and shall be field installed. Endcaps shall also be mechanically fastened on the underside of each plank with rivets and have smooth edges for safety.
CLIP SETS
Clip sets shall adequately connect seal and foot planks to the supporting structure so as to transmit all design loads to the understructure members as specified in the design section. All planks shall be connected to the supporting structure using four way adjustable clips, carriage bolts and flange nuts of 5/16″ steel with a hot dipped galvanized finish.
SPLICE CONNECTORS
Internal splices, where required, shall be two per joint aluminum alloy 6061-T6 and shall penetrate the joint a minimum of 8 inches in each direction and be fastened at one end only to allow for contraction and expansion.
ANCHOR BOLTS
Anchor bolts shall be 3/8″ diameter x 2-3/4″ long “wedge type” concrete anchor, with a minimum of 1-5/8″ penetration in concrete foundation as specified below. The anchor bolt load capacity shall met the minimum working load requirements of a tension capacity of 1200lbs. and a shear capacity of 1300lbs. These loads shall be based on testing conducted according to ASTM standard E488 and in compliance with AISI, UL, FM and ICBO.
FOUNDATIONS
The bleacher system uplift anchoring system has been designed with the assumption of the concrete foundation meeting a minimum of 3500 P.S.I. compressive strength which is in full compliance with ACI 318 and 301 (American Concrete Institute, Specifications for Structural Concrete for Buildings). The foundation system shall be designed to meet the following minimum loading requirements:
Bleacher System Frames typically at 6′-0″ o.c.
Bleacher frame base uniform total loading D.L. plus L.L. 700 plf (unfactored)
Bleacher frame base uniform wind uplift loading 250 plf (unfactored)
Siesmic Loading Requirement per local requirements