Dynamic load allowance of long-span modular steel bridges: Fid-Bau Portal

Dynamic load allowance of long-span modular steel bridges

Chordà-Monsonís, J. / Moliner, E. / Galvín, P. / Martínez-Rodrigo, M.D. / Zacchei, E. / Tadeu, A. / Ferraz, I. / Romero, A.

Abstract

Abstract Modular steel bridges are structures whose construction is based on regular prefabricated truss units. This presents several advantages, such as rapid and easy deployment, high adaptability to the terrain and reduced construction costs. However, they generally face operational restrictions for span lengths greater than $60 m$ . Recent technological innovations search to overcome these limitations and develop modular structures with larger spans. Hence, the main objective of this work is to evaluate the dynamic effects on long-span modular steel bridges. The present contribution provides a study on two modular bridge typologies, considering different span lengths from 120 to $140 m$ . A 3D coupled vehicle–bridge model is used to analyse the vehicle–bridge interaction and the dynamic load allowance of the structures. The vehicle is represented as a multibody truck system and the bridges are modelled with the finite element method. Several types of randomly-generated road irregularities are considered on the bridge deck. The effect of each type of irregularity is evaluated on the dynamic load allowance of the bridges. The results obtained reveal the notable influence of road irregularities that involve abrupt vertical displacements that excite the vehicle mode shapes. In addition, it is observed that dynamic load allowance indices tend to decrease with longer spans and higher speeds, except when a resonance is produced.

Highlights • Dynamic load allowance of truss bridges considering very long spans (120–140 m). • The dynamic effects on two bridge typologies are studied. • Higher dynamic amplification due to road defects exciting the bouncing of the vehicle. • Velocity of the vehicle tends to decrease dynamic load allowance except at resonance. • Inconsistencies detected in dynamic load allowance definitions in some design codes.