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Document Type: TechNote Product(s): LEAP CONSPAN Version(s): All Original Author: Bentley Technical Support Group
Document Type: TechNote
Product(s): LEAP CONSPAN
Version(s): All
Original Author: Bentley Technical Support Group
The distribution factor is the Reaction, R, about the Hinge.
Case (A). If Only One Lane is LoadedThe first axle is placed 2 feet from the face of the curb. The reaction is computed by summing moments about one support to find the reaction at the other support by assuming that the supported component is hinged at interior supports.
If P is lane (axle) load, then R × (16) = 0.5 × P × (20) + 0.5 × P × (14) R = 0.5 × P × (34) / (16) R = 0.5 × P × (2.125)
Multiple Presence Factor for single lane loaded = 1.20 R = 0.5 × P × (2.125) × 1.20 R = 1.275 P
Case (B). If Two Lanes Are LoadedIf P is lane (axle) load, then R × (16) = 0.5 × P × (20) + 0.5 × P × (14) + 0.5 × P × (8) + 0.5 × P × (2) R = 0.5 × P × (44) / (16) R = 0.5 × P × (2.75)Multiple Presence Factor for two lanes loaded = 1.00 R = 0.5 × P × (2.75) × 1.00 R = 1.375 P
The distribution factor using Lever Rule is taken as the larger of these two cases, whichin this case, is 1.375.
The distribution factor is the Reaction, R, is independently computed about the Hinge onboth the right and the left sides.
Case (A). If Only One Lane is LoadedThe first wheel line is placed directly over the interior girder of interest to generate the largest reaction. Since the girder spacing is only 16 feet, it cannot accommodate an additional two axles from a second truck on the right hand side. The reaction is computed by summing moments about the right hinge.
If P is lane (axle) load, then R × (16) = 0.5 × P × (10) + 0.5 × P × (16) R = 0.5 × P × (26) / (16) R = 0.5 × P × (1.625)Multiple Presence Factor for single lane loaded = 1.20 R = 0.5 × P × (1.625) × 1.20 R = 0.975 P
Case (B). If Two Lanes are LoadedIn addition to the axles placed to the right of the interior beam, two other wheel lines can be placed to the left of the interior beam being studied. The reaction is computed by summing moments about the hinges independently on the right side and then the left sideas shown below.If P is lane (axle) load, then R × (16) = 0.5 × P × (10) + 0.5 × P × (16) + 0.5 × P × (6) + 0.5 × P × (12) R = 0.5 × P × (44) / (16) R = 0.5 × P × (2.75)Multiple Presence Factor for two lanes loaded = 1.00 R = 0.5 × P × (2.75) × 1.00 R = 1.375 P
Case (C). If Three Lanes are LoadedIn addition to the axles placed for the two-lane loading, two more axles are placed, if theyfit, to the right. The reaction is computed by summing moments about the hinges independently on the right side and then the left side as shown below.
If P is lane (axle) load, then R × (16) = 0.5 × P × (10) + 0.5 × P × (16) + 0.5 × P × (6) + 0.5 × P × (12) +0.5x P × (4) R = 0.5 × P × (48) / (16) R = 0.5 × P × (3.0)Multiple Presence Factor for two lanes loaded = 0.85 R = 0.5 × P × (3.0) × 0.85 R = 1.275 PThe distribution factor using Lever Rule is taken as the largest of these three cases, which in this example is 1.375.
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