Balancing of Movable Bridges by the Strain Gauge Technique

Case Study No. 4poute 1&9 Vertical Lift B ridse Over the Passaic RiverThe Passaic River Route 1&9 vertical lift bridge carries two (2)lanes of traffic in both the east and westbound directions acrossthe Passiac River in Newark, New Jersey. Each end of the span isindependently operated by separate machinery controlled by thebridge operator. There is a pinion-bull gear-sheave assembly overwhich wire ropes run attached at one end to the span and the otherend to the counterweight.A 2000 pound generator was left on the bridge during the testprogram. This condition was not noted until the completion of thetest program. The generator load produce 0.07% of dead load errorin the northwest cable group. This effect was accounted for duringthe final balance calculations.The frictional forces were found to be substantially high on theeast tower, several times higher than the balance goal.The desired 1% span heavy condition was achieved when consideringeach end as a unit. Further attempts to improve the individualcorners would be questionable considering that the frictionalforces are substantially greater than balance goal.