Identification of flutter derivatives from full-scale ambient vibration measurements of the Clifton Suspension Bridge

Abstract

Abstract. The estimated response of large-scale engineering structures to severe wind loads is prone to modelling uncertainties that can only ultimately be assessed by full-scale testing. To this end ambient vibration data from full-scale monitoring of the historic Clifton Suspension Bridge has been analysed using a combination of a frequency domain system identification method and a more elaborate stochastic identification technique. There is evidence of incipient coupling action between the first vertical and torsional modes in strong winds, providing unique full-scale data and making this an interesting case study. Flutter derivative estimation, which has rarely previously been attempted on full-scale data, was performed to provide deeper insight into the bridge aerodynamic behaviour, identifying trends towards flutter at higher wind speeds. It is shown that, as for other early suspension bridges with bluff crosssections, single-degree-of-freedom flutter could potentially occur at wind speeds somewhat below requirements for modern designs. The analysis also demonstrates the viability of system identification techniques for extracting valuable results from full-scale data.

Effects of oscillation amplitude on motion-induced forces for 5:1 rectangular cylinders

“…This is similar to the findings for thin rectangular cylinders (Noda et al, 2003), where the A 2 * is strongly affected by torsional amplitude. Similar trends can also be verified by extracted flutter derivatives in full-scale for a real instabilityprone bluff bridge (Nikitas et al, 2011). Fig.…”

Performance of Optical Structural Vibration Monitoring Systems in Experimental Modal Analysis

“…Beyond the 4th mode, all image-based MCS yield little accuracy in terms of damping and generalised mass reconstruction. The identified damping levels are representative of those measured on bridges, chimneys, and steel masts and towers [24,[47][48][49][50][51].…”

Rapid deployment of a WSN on the Clifton Suspension Bridge, UK

“…The system could also be evaluated against previous monitoring systems. The size and structure of the bridge also makes it convenient for study: small enough that the complete bridge can be monitored and understood, but large enough and flexible enough to exhibit some interesting dynamic behaviour (Macdonald, 2008;Nikitas et al, 2011). The CSB's function as a toll bridge means that existing traffic monitoring infrastructure might provide information about vehicles.…”

“…Webb et al, 2015). This iconic structure is the subject of ongoing research such as the vibration response caused by pedestrians and wind loading (Macdonald, 2008;Nikitas et al, 2011). However, the structural response has not previously been correlated with vehicular use (e.g.…”