Lattice Girders - 3 Bar / 4 Bar

1. All lattice girders shall consist of three or four primary retaining bars connected by stiffening elements of the manufacturer's design. The lattice girder will be designed to allow shotcrete to penetrate into and behind the girder with a minimum of shotcrete shadows. 2. DSI Underground offers various alternate stiffening element systems:

• Traditional spiders
• Romtech^™ sinoidal waves
• Box systems for four-bar designs

Specific details of the above can be provided upon request. All connections between stiffening elements and the retaining bars will be by gas metal arc welding. 3. The lattice girders will have moment properties about the neutral axis as shown. A minimum of 5% of the moment of inertia shall be provided by the stiffening elements. This percentage will be calculated as an average along a repeatable length of the girder. 4. The maximum centerline spacing of stiffening elements shall be less than three times the height of the girder to assure stability over buckling with a tolerance of plus or minus 1 inch. 5. The connection elements at the end of the girder may be made with structural plates, angles or tunular couplers. The footplates must be able to transfer the load to the soil or rock in the invert. The connecting elements must be able to transfer the full load capacity of the girder.