Modal Identification of a Pedestrian Bridge by Output-Only Analysis

摘要

Modal parameters (natural frequencies, mode shapes and damping ratios) describe the dynamic properties ofrnmechanical systems. Classical modal analysis, based on Frequency Response Function, require measurement ofrnboth input force and response. Normally, it is very difficult to measure the excitation on large structures (bridges,rntall buildings, offshore platforms, etc.). However, reasonable estimates of modal parameters can be extractedrnfrom ambient vibration or output-only response (wind, traffic, humans, etc.).rnThe dynamic behaviour of a curved pedestrian bridge in the Cartuja Campus of the Universidad de Sevilla (Spain)rnhas been investigated by full-scale testing and numerical models. Nine vibration modes have been identified inrnthe frequency range of 0-30 Hz, by the following algorithms: Enhanced Frequency Domain Decompositionrn(EFDD) and Stochastic Subspace Identification (SSI).rnModal parameters estimated from ambient response are compared with those obtained from a three-dimensionalrnfinite element model. Both sets of results show very good agreement.