ABSTRACT
Current bridge inspection methods rely largely on visual examination to evaluate bridge condition. Remote bridge monitoring systems (RBMS) using measured structural vibration have been perceived to assist in bridge inspection. However, sensitivity of measured modal properties for RBMS is critical for practical application. A study was conducted at New York State Department of Transportation (NYSDOT) to examine sensitivity of modal parameters in detecting fatigue cracks, including frequencies, mode shapes, and their derivatives. Modal tests were conducted on a 1/6 scale model of a multiple-steel-girder simple-span bridge and on a simply supported fracture-critical steel bridge, including both intact and damaged states. Statistical methods were used in analyzing the results for detecting practically visible damages. Results indicate that modal frequencies in conjunction with mode shapes may be used to identify the existence of bridge damage as small as 6 cm long. However, it is difficult to identify the damage location using these modal parameters.
