Bridge Health Monitoring for a Beam Bridge using Damage Model and Slope Sensors

The use of Bridge Health Monitoring systems has the potential to provide greater confidence in the integrity of a bridge. As a result, the life of a bridge can be maximized by reducing whole life costs and providing additional safety measures. Structural damage detection and integrity assessment is one of the fundamental objectives for Bridge Health Monitoring. In such an application, early stage damage detection is desirable by examining changes in its measured responses, especially bridge deflection. Until now, it is believed that such a parameter is the most reliable indicator to overcome difficulties in bridge measurement with workable signal to noise ratio. Structural vibrational responses are the most commonly used measurements in part due the hypothesis that damage changes the physical properties of a structure, which in turn will cause changes in the vibrational characteristics of the structure. Vibration-based damage detection is a rapidly developing technology and a number of methods have been proposed.;A new factor called the Modal Flexibility Participating Factor (MFPF) is introduced, which is a good measure of changes in the structural characteristics. First, it is sensitive to bridge damage and can be directly used to indicate damage. Secondly, MFPF itself is robust and insensitive to measurement noise. One of the major improvement is the use of mode shape in bridge damage model. Mode shapes were used in the study since they are orthogonal i.e. mode shape for a system is linearly independent of all other mode shapes for the system. Hence, mode shapes can move independently in the sense that excitation of one mode will never cause motion of a different mode. Also, mode shape for a system changes if and only if there is a change in the physical characteristics and/or boundary conditions of the system.;The modal parameters (including natural frequencies, mode shapes, phase angles, and coherence function) of the I-beam are collected using Modal Analysis (in laboratory using Impact Hammer modal testing). Also, finite element method is used to obtain mode shapes of the I-beam using ANSYS. The mode shapes are then used to represent I-beam deflection because deflection is time variable, and robust bases are vital to stably represent deflection. These same shapes tend to dominate the motion during an earthquake, vehicle motion, windstorm, etc.;The proposed damage model has been tested for different type of loadings and beams using numerical simulations. From these tests it has been evident that the damage model can significantly increase signal to noise ratio and is a good indicator of damage. The change in MFPF, when damage occurs, with change in natural frequency and change in specific location of mode shape together, will provide better indications of damage. However, if these modal parameters are used individually, the values of change are almost negligible. Hence the individual modal parameters cannot be used to indicate bridge damage. Very often, the change in individual modal parameters will be buried by measurement noises. In other words, poor signal to noise ratio is the main reason that we cannot use individual modal parameters to indicate bridge damage. Real life bridge (i.e. Bridge 263) was also tested for deflection values under dynamic loading. The deflection calculation system (i.e. slope sensors) were installed on the bridge and data was collected without interrupting the traffic. The data was analyzed using deflection calculation software and a dynamic deflection testing report was generated. The dynamic testing report further corroborates on the robustness of the deflection calculation system. (Abstract shortened by UMI.).