Vertical Lift Bridge Structural Imbalance Testing

Lift bridges are critical for the coexistence of rail and ship traffic in dense urban areas. At points where waterways and rail lines intersect, the entire over-water portion of the bridge rises for ships to pass and then lowers again to allow trains to cross.  An imbalance in this lift bridge caused CONRAIL to call on RRJ for a solution.

RRJ’s test data indicated the bridge was overly span-heavy. The bridge had to be pulled closed because friction exceeded the amount of imbalance. Final adjustments included adding 9,000 pounds to each counterweight to reduce the imbalance level while maintaining a safe, slightly span-heavy state.

How RRJ helped

• Structural imbalance testing
• Measure torsional shear strains
• Correct for undesirable bending and beam shear effects.
• Acquire data recordings of shaft torque
• Calculate the degree of imbalance
• Calculate amount of friction present