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LATTICE GIRDE;tr

.IJ--ACIAMERICAN COMMERCIA

INCORPORATED


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Lattice GirdersUsed in conjunction with shotcrete supportAmerican Commercial Inc. has been a leader in thedevelopment and manufacturing of undergroundsupport systems for over 80 years. AmericanCommercial Inc. has the rights to produce and marketthe Pantex Lattice Girders. Pantex Stahl AG is theoriginator of the "Pantex" lattice girder and is theleadingsupplier of these girders for the NATMsystemsin Europe.Lattice girders serve some of the same basic functionsin tunneling as steel arch supports. They are part ofthe temporary lining which initially supports theexcavationand, in some cases, are part of the finishedlining. Usedwith the New Austrian Tunneling Method(NATM)of shotcrete application, lattice girder systemsoffer a very economical alternative to other supportmethods for a wide variety of ground conditions.

OrmeStreet Phase III - Bradshaw Construction

ApplicationsThe use of lattice girders should be considered forprojects where shotcrete will be used for temporary orpermanent support. These include mining through softground, mixed face and rock tunnels, in which widthsor heights may vary. Lattice girders are applied equallywell to circular and horseshoe shaped excavations,whether driven full face or heading and bench.Easier to handleLattice girders are light and easy to install safely byhand. The use of lattice girders in conjunction withshotcrete reduces material handled in the tunnel.Crew sizes can be reduced because the supports,which are much lighter than conventional steel arches,can be handled easily without special equipment.Shotcrete applicationThe main advantage of the Lattice Girder is its ability inworking with shotcrete. It provides a more efficientbond with the shotcrete strength. Because of the opennature of the lattice beam's construction, shotcretepasses through it readily, reducing the possibility ofunconsolidated shotcrete areas behind the beam. Theshotcrete can be applied evenly producing a superior,integral lining.

Advantages For The Use of Lattice GirdersLattice girders provide the following advantages:. Immediate roof support over the excavated section.. Act as a template assuring a minimum thicknesswhen applying shotcrete..Become part of the reinforcement in the shotcretelining.

. Provide support for spilling, if needed, over the nextexcavation area.

. Work equally well with machine mining or drill andshoot tunneling - no need for major investment inspecial equipment.

. Are practical supports for a wide range of groundconditions.

. Can be erected within a few minutes by a small crewwithout special handling equipment.


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antex Lattice Girders I 3-Barsi th spaced diagonals, three bars are assembled to form a girder. The single bar can beocated against the ground or towards the inside of the tunnel, fitting a specified designeometry. The spaced stiffening elements reduce the local buckling length of the bars,sure a high normal and bending moment resistance, and secure a transfer of lateral forcesthe lining before the shotcrete has reached its design strength.-Bar Lattice Girder Properties

antex Lattice Girders I 4-Barsth spaced diagonals, four bars are assembled to form a girder. Fabrication of the girdero the design geometry is possible. The spaced stiffening elements reduce the localckling length of the bars and assure a high normal and bending moment resistance andsecure transfer of lateral forces in the lining before the shotcrete has reached its design

-Bar Lattice Girder Properties

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C.P. BAR WEIGH H B e H1 Ix Sx Iy Sy JOINTPLATE FOOTPLATESIZE SIZE LENGTHUNITW SIZE UNITWTYPE S, S, S, (Ibslft) (in) (in) (in) (in) (in') (in') (in') (in') (in) (in) (Ibs) (in) (Ibs)

6 8 C> 6.72 3.70 3.94 2.01 3.441 1.716 2.324 1.180 49/16 3.2 3I8x5x5 2.7e,.,50 6 10 c.q 8.26 3.94 1.88 4.676 2.226 2.395 1.216 49/16 3.26 8 6.95 4.50 2.42 5.544 2.295 5.064 1.846 r- 55/16 3.5C> .j:>.70 6 10 e,., 8.59 4.77 5.50 2.20 2.75 7.375 2.886 5.135 1.867 >< 51/2 3.7 3/8x6x6 3.8c.q (J.)8 11 11.93 5.16 2.69 12.108 4.465 8.226 2.991 >< 53/4 3.96 8 7.07 5.50 2.94 8.937 3.036 8.950 2.526 (J.) 69/16 4.4C> ex;95 6 10 8.70 5.77 7.09 2.59 3.75 11.741 3.751 9.028 2.548 >< 63/4 4.6 3/8x7x8 6.08 11 12.05 6.16 3.18 18.883 5.854 14.840 4.188 71/16 4.86 8 7.94 6.25 3.37 12.182 3.636 13.906 3.21 711/16 8.0C>

15.849 4.416 13.985 r- 713/16 8.1 /8x8x91/215 6 10 9.58 6.52 8.66 2.91 4.50 3.229 CJ1 8.18 11 12.92 6.91 3.63 25.208 6.953 23.342 5.390 >< 81/8 8.4(J.)6 8 7.76 6.87 3.67 15.015 4.088 13.906 3.211 >< 81/8 8.4C> i\3 85/16 8.6 /8x8x9 1/230 6 10 :'" 9.39 7.14 8.66 3.15 5.12 19.379 4.929 13.977 3.229 8.1'i >


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GENERAL REQUIREMENTS1. All lattice girders shall consist of three or four primary retaining bars connected by stiffening elements of the manufacdesign. The lattice girderwill bedesigned to allow shotcrete to penetrate into and behind the girder with a minimum of shoshadows. The stiffening elements will be made of one single formed smooth bar. The connection between stiffening eleand the retaining bars will be by gas metal arc welding.

2. The lattice girders will have moment properties about the neutral axis as shown. A minimum of 5% of the moment ofshall be provided by the stiffening elements. This percentage will be calculated as an average along a repeatable lengthgirder.3. The maximum centerline spacing of stiffening elements shall be less than three times the height of the girder to astability over buckling with a tolerance of plus or minus 1".4. The connection elements at the end of the girder may be made with structural plates, angles or tubular couplers. Thplates must be able to transfer the load to the soil or rock in the invert. The connecting elements must be able to transffull load capacity of the girder.FABRICATION:

1. Lattice girder segments shall be composed of a low alloy steel used for concrete reinforcement and intended for sapplicationswhere bending and welding are of importance.2. Minimum physical properties of steel:TensileStrength minimum 80 ksiYield Strengthminimum 70 ksiUltimate Elongation minimum 10%3. The connection elements at the end of the girder shall be constructed of structural angle or plate meeting the minpropertiesofA36. Bolts and nuts shall meet the requirements of A325 unless otherwise noted.4. Welding process to meet the requirementsset forth byAWS for gas metal arc welding (GMAW). All welders must be cein accordancewithAWS D1.1. All welds will run parallel to the retaining bars with a minimum length of 1".

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AMERICAN COMMERCIAL=a~"""='=J:J"T""E:D

Corporate Office and Bristol Plant. 200 Bob Morrison Boulevard. Bristol, VA 24201-3810Tel (540) 466-2743. Fax (540) 669-0940

Louisville Operation and Plant. 1032 East Chestnut Street. Louisville, KY 40204-1019Tel (502) 473-1010. Fax (502) 473-0707www.americancommercial.com

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