Vibrations of Curved Spans for Mass Transit

Nondimensional dynamic responses of simple and multiply-supported, horizontally curved beams with moving loads are measured in laboratory-scale experiments. Effects of system parameters involving span stiffness, arc length, frequency, end support constraints, and various transit load speeds and spacings are investigated. For critical combinations of certain parameters, adverse coupling of bending and torsional span responses are observed. For instance, as critical load speeds are approached, measured twist angles and bending strains at midspan approach unboundedness for multiple spans, but are bounded for equivalent simple spans placed end-to-end. Calculations based on Bernoulli-Euler curved beam theory (with negligible warping rigidity) complement these simple span measurements. Experiments also include multiple spans with up to 90? turns, subject to both transit point loads in tandem and sprung vehicles. Results are applicable to dynamic span designs for mass transit systems.