DYNAMIC CHARACTERIZATION OF A LONG-SPAN BRIDGE - A FINITE-ELEMENT BASED APPROACH

Aging bridges coupled with increasing traffic loads are producing a se vere toll on the nation's infrastructure. This has made it necessary t o take a closer look at the health of existing bridges and develop aut omated damage identification methods if possible. Recent works in the field of structural dynamics have shown that damage detection techniqu es utilizing parameters like mode shapes, modal frequencies and dampin g ratios can be used to identify damage in structural systems. It is, however, important to be able to establish a baseline model for the st ructure first, and then a model updating technique can be utilized to evaluate the condition of the structure from time to time. It is with this goal in mind that the authors have decided to establish the proce ss for obtaining a baseline model for a long span bridge. Based on the actual design drawings of a bridge, finite element (FE) models of the bridge in question are developed using SDRC-IDEAS. Three models of th e bridge are simulated using Normal Mode Dynamics solver in SDRC-IDEAS to obtain the modal parameters of interest, in this case the modal fr equencies and the mode shapes. A modal assurance criteria (MAC) is uti lized to compare the different simulated mode shapes and, finally, the modal frequencies that have been obtained from the FE analysis are co mpared to frequencies that have been obtained from some preliminary fi eld tests. (C) 1997 Elsevier Science Limited.