Nondestructive evaluation and health monitoring of highway bridges.

摘要

This research seeks the rational organization and integration of nondestructive evaluation (NDE) technologies, the methods of structural identification, and concepts of reliability and fault detection, each according to its merits, within a system devoted to monitoring the state-of-health of an instrumented structure. A global NDE methodology has been developed based upon the structural identification concept, employing truckload testing, modal testing , and instrumented monitoring as its principal experimental tools. The test results are transformed to both strain influence lines and modal flexibility, which have been demonstrated to be a conceptual, quantitative, comprehensive, and damage-sensitive signature. These parameters also provide an accurate condition index, since it may be used to conveniently obtain the stress profiles and deflected shapes of a bridge under any loading pattern. The capacity rating for the instrumented section and/or an estimation of the remaining fatigue life for the instrumented member/connection based upon the relevant AASHTO codes can be obtained immediately following the controlled truckload testing of the bridge.; This methodology has provided several unique deliverables to the aforementioned field of expertise: (1) The application, verification, and assessment of truckload testing, modal impact testing, and long-term monitoring procedures, as well as their necessary sensor types and positioning, for several highway bridges. (2) A reduced set of quantitative models for the estimation and identification of single and multiple span beam response to truckload and impact in both the time and frequency domains. (3) The quantitative evaluation of the most promising damage indices for the detection of induced damage-types on a decommissioned specimen. (4) The quantitative identification of AASHTO condition indices and their requisite assumptions from the acquired field data.; The most important contribution of this research is an objective technique for the accurate field identification of bridge parameters (specifically, strain influence lines and modal flexibility) which not only provide for the timely assessment of structural condition but are also sensitive to typical damage scenarios. These results are achieved without a finite element model, but can also serve to calibrate such a model for greater spatial precision and the investigation of other possible damage scenarios, repair/retrofit schemes, and other structural considerations.