Study of Time-Domain Techniques for Modal Parameter Identification of a Long Suspension Bridge with Dense Sensor Arrays

摘要

While numerous studies have been published concerning the application of a variety of system identification techniques inconjunction with vibration measurements from civil infrastructure systems, there is a paucity of publications addressing the influence ofalgorithm-specific control parameters that impact the correct and efficient application of the selected identification scheme. Furthermore,as dense sensor arrays become widely accessible in civil infrastructure applications, voluminous amounts of multichannel data streams arebecoming available for processing, thus imposing new demands on identification procedures regarding high-dimensionality (in both thespatial as well as the temporal domains) requirements that may render some methods inapplicable if careful attention is not paid topractical implementation issues. This paper provides a comprehensive study of three time-domain identification algorithms applied inconjunction with the Natural Excitation Technique in order to extract the modal parameters of a newly constructed long-span bridge thatwas monitored, in its virgin state, over a relatively long period of time with a state-of-the-art dense sensor array. The three methods usedare: the eigensystem realization algorithm (ERA), the ERA with data correlations, and the least squares algorithm. One of the criticalissues in the mentioned algorithm's, is selection of the reference degree-of-freedom (DOF). Previous experiences have shown that onecannot rely on a single reference DOF for identification of all modes. Consequently, the aforementioned identification formulations weremodified to include multiple reference DOF, simultaneously, or one at a time. An autonomous algorithm was presented to distinguish thegenuine structural modes from spurious noise or computational modes. Based on some parameter studies, some useful guidelines for theselection of critical user-selectable parameters are presented.