Abstract
Vibration measurement method is utilized simply to evaluate bridge's structural performance. Structural properties are mainly influenced by fatigue, material deterioration and earthquakes. These factors cause the changes of frequency characteristic due increasing of lateral displacement and decreasing of stiffness. Therefore, damage identification of a structure can be assessed by grasping its vibrational property. Conventional vibration measurement was generally conducted by using accelerometers. In recent years, a long distance, non-contact, and easily-assembled LDV (Laser Doppler Velocimeter) has been developed. Without requiring on-structure sensor installation and having huge flexibility under variety of measurement environments made LDV measurement technique attractive and to be considered as better than other non-destructive investigation methods. This study targeted in-service bridges by measuring their natural frequencies and displacements using two LDV devices. Measuring numerous spots with two LDV devises enables to achieve high accuracy and reliability to verify the most-scrutinized structural vibration mode shape. Furthermore, the field-measured-based analyzed results were compared with three-dimensional FEM model analyses to evaluate the validity of the analytical model and to grasp the structural vibration characteristics of measured-bridges.
