Vibrations of simple beam-like modelled bridge under harmonic moving loads

This paper concerns the study of a simple beam-like modelled bridge traversed by a concentrated moving load that varies during the transit time. The aim is to determine useful and propaedeutical results in order to study the effects of combined loads transmitted both by a single axle (constant component + harmonic components) and by multiple axle subsystems equally spaced. In particular, we reconsider the case of constant load, refining the results available in the literature, and propose some new aspects that are essential for the final analysis. We analyze the concept of critical speed and we argue that in the present context it does not have great significance. We also consider how the phase and frequency of the harmonic load affects the calculation of the deflection of the bridge.