Resonance and cancellation phenomena in two-span continuous beams and its application to railway bridges

• The objective of this study is to evaluate the vibratory response of two-span continuous beams subjected tomoving loads and, in particular, to investigate the maximum resonance and cancellation of resonance phenomena.The main practical interest is the evaluation of the maximum acceleration response in railway bridges,which is one of the most demanding Serviceability Limit States for traffic safety according to current regulations.Two-span continuous bridges, in their simplest version (i.e. uniform identical spans), present antisymmetric andsymmetric modes with closely spaced natural frequencies, leading to a more involved dynamic behaviour thanthat of simply-supported bridges. First, the free vibration response of a Bernoulli-Euler two-span beam after thepassage of a single load at constant speed is formulated analytically, and non-dimensional speeds leading tocancellation or maximum response in free vibration are obtained for each mode. Then, these conditions areequated to resonant speeds induced by equidistant load series, and span length-to-characteristic distance ratioscausing cancelled out resonances, or remarkably prominent ones, are obtained. Based on the previous derivations,a methodology for detecting which could be the most aggressive trains for a particular structure based onpure geometrical considerations is discussed. Finally, the applicability of the theoretical derivations is shownthrough the numerical analysis of two real bridges belonging to the Swedish railway network.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Infrastrukturteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Infrastructure Engineering (hsv//eng)

Nyckelord

Railway bridges; Two-span continuous beams; Resonance; Cancellation; Moving loads

Bro- och stålbyggnad

Structural Engineering and Bridges

Publikations- och innehållstyp

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