Abstract Summary
In this work, the dynamic response of six portal frame bridges are experimentally evaluated through full-scale controlled dynamic testing. The study aims to (i) experimentally identify the modal characteristics of portal frame railway bridges with different span lengths and subsoil conditions, (ii) provide high-quality experimental data that can be used for system identification and experimental validation of numerical models; and (iii) study the influence of Soil-Structure Interaction (SSI) on the fundamental modal parameters and resonant response of bridges. In the case of short span bridges, the measured modal properties identify the substantial contribution of the surrounding soil on the global damping of the system and highlight the importance of the SSI on the dynamic response. On the contrary, the identified fundamental damping ratios of the long span bridges are in the range of the recommended design values and seems not to be influenced by the SSI effects. The results show that there is a need to review the recommended modal damping ratios for this type of bridges in the code provisions and design manuals.
