Dynamic Performance of a Slender Truss Bridge Subjected to Extreme Wind and Traffic Loads Considering 18 Flutter Derivatives

Abstract

The aerodynamic performance of long-span bridges under extreme environmental conditions, such as under strong winds and heavy traffic, is critical for bridge design. Either free vibrational or forced vibrational tests are usually carried out to obtain the flutter derivatives, either traditional eight flutter derivatives from two-degree-of-freedom (2-DOF) model tests or 18 flutter derivatives from 3-DOF model tests, to evaluate structural dynamic performance. In the present study, an experimental facility is developed based upon a digitally controlled 3-DOF forced vibration system to enable the extraction of 18 flutter derivatives of bridge decks through wind-tunnel tests. After validating the proposed forced vibration test facility using typical section types, i.e., a thin-plate section and a truss-girder section, the 18 flutter derivatives for the truss-girder section are extracted and used for bridge dynamic performance assessment considering combined loads from traffic and wind. The case study of a truss bridge shows that ignorance of the additional 10 flutter derivatives can result in a significant overestimation of the bridge lateral responses, especially under high wind speeds. However, ignorance of the additional 10 flutter derivatives on the bridge vertical and torsional responses, as well as on the dynamic responses of the running vehicles, are not significant. Similar observation were also applied to the stress responses at the critical location of the bridge deck.