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(overlap) on each anchor bar. Both sides of each anchor bar will be welded to the frame. Rock bolts shall <br />protrude through holes drilled in the grate frame. Torch-cut holes will not be accepted. Rock bolts will be <br />tightened securely and the nuts tack welded. The grate material will then be positioned onto the secured <br />frame and welded at every other bearing bar, one side, around the entire perimeter of the grate. Painting is <br />not required. <br />If a hinging and locking mechanism is required, the hatch and hatch frame will be welded into the center area <br />of the grate. The locking door shall be constructed as shown on Standard Drawing Number 6. The grating <br />material shall be the same as the surrounding grating. <br />All voids along the edges of the grating larger than one inch (1 ")must be filled with bolt protection plates where <br />anchor bars or bolts are exposed from above, or pieces of welded grating or angle to fill the void. <br />Following installation of the grating, the CONTRACTOR shall weld a 3" inside diameter 4" long steel pipe to <br />the grating, the brass cap, provided by the owner, shall be grouted flush to'/a" below the top of the pipe using <br />non-shrink grout such as Pour Rock, Kwik-Crete, Epoxy Bond, or Moly Parabond. <br />8.3.3. Beams <br />Steel beams will be used to reduce all grating spans to a maximum as shown below. For shaft spans of <br />twelve feet (12'), or less, W4 x 13 steel beams will be used. For shaft spans between twelve feet (12') and <br />twenty feet (20'), W6X20 steel beams shall be used. <br />Table 10.1 <br />~7 <br />Bearing Bar Size Bearing Bar Spacing Cross Bar Spacing Maximum Grating <br />1-1/4" x 1/8" 1-3/16" 4„ San feet <br />3 <br />5 <br />1-1/4" x 1/8" 15/16" 2" . <br />4 <br />0 <br />1-1/4" x 3/16" 1-3/16" 4" . <br />4 <br />0 <br />1-1/4" x 3/16" 15/16" 2" . <br />4 <br />5 <br />1-1/2" x 1/8" 1-3/16" 4" . <br />4 <br />5 <br />1-1/2" x 1/8" 15/16" 2" . <br />5 <br />0 <br />1-1/2" x 3/16" 1-3/16" 4" . <br />5 <br />0 <br />1-12/" x 3/16" 15/16" 2" . <br />5 <br />5 <br />1-3/4" x 3/16" 1-3/16" 4" . <br />5 <br />5 <br />1-3/4" x 3/16" 15/16" 2" . <br />6 <br />0 <br />2" x 3/16" 1-3/16" 4" . <br />6 <br />0 <br />2" x 3/16" 15/16" 2" . <br />6 <br />5 <br />2 1/4" x 3/16" 1-3/16" 4" . <br />6 <br />5 <br />2 1/4" x 3/16' 15/16" 2° . <br />6 <br />5 <br />2 1/2" x 3/16" 1-3/16" 4" . <br />6 <br />5 <br />2 1/2" x 3/16" 15/16" 2" . <br />7.0 <br />Steel beams will be embedded and covered in concrete for the entire length of the beam that rests on the <br />footing surface, except for the top portion where grating will be placed. The steel beams must extend to the <br />edges of the grating. Grating may be set on steel beams immediately following the embedment of beam ends <br />in concrete. Where grating crosses a support beam, every other bearing bar shall be welded for a length of <br />~ one inch to the support beam. Paint, if any, will be wire brushed or ground off beams prior to welding. <br />8.3.4. Installation Within Historical Structures <br />Gratings constructed within wooden headframe structures will require modifications to conform to the existing <br />~ support columns. Custom fitting and welding operations while the grate is in the structure will be allowed if the <br />adjacent wood is adequately protected from sparks or flames, and only when an approved fire extinguisher is <br />~ at the site. Additional connector plates, stiffeners or other steel reinforcing elements may be required to <br />Colorado Division of Minerals and Geology GENERAL BID SPECIFICATIONS <br />~ 2004 ~ Page 41 <br />