This study investigated a number of different damage detection algorithms for structural health monitoring of a typical suspension bridge. The Alfred Zampa Memorial Bridge, a part of the Interstate 80 in California, was selected for this study. The focus was to implement and validate simple damage detection algorithms for structural health monitoring of complex bridges. Accordingly, the numerical analysis involved development of a high fidelity finite element model of the bridge in order to simulate various structural damage scenarios. The finite element model of the bridge was validated based on the experimental modal properties. A number of damage scenarios were simulated by changing the stiffness of different bridge components including suspenders, main cable, bulkheads and deck. Several vibration-based damage detection methods namely the change in the stiffness, change in the flexibility, change in the uniform load surface and change in the uniform load surface curvature were employed to locate the simulated damages. The investigation here provides the relative merits and shortcomings of these methods when applied to long span suspension bridges. It also shows the applicability of these methods to locate the decay in the structure.
This study introduces an efficient procedure to estimate the structural response of a suspension bridge in real-time based on a limited set of measured data. Unlike conventional techniques, the proposed procedure does not employ mode shapes and frequencies. In this study, the proposed technique is used to estimate the response of a suspension bridge structure based on a set of strain gauge measurements. Finite element analysis is performed only once to set up the structural parameters, namely computed flexibility matrix, and computed hanger forces matrix. The response of the bridge was estimated without any additional finite element analysis using the computed structural parameters and the measured hanger strains. The Alfred Zampa Memorial Bridge, on Interstate 80 in California, was selected for this study. A high fidelity finite element model of the bridge was developed using the general purpose computer program ADINA. The proposed method has been proven to have the capability to estimate any type of structural response in real time based on the measured hanger strains, and provides an important part of an integrated Structure Health Monitoring (SHM) system for major bridges.
This article describes the development of a fiber optic accelerometer based on Fiber Bragg Gratings (FBG). The
accelerometer, designed for the structural health monitoring of bridges, utilizes a lumped mass attached to a stretched
FBG. Acceleration is measured by the FBG in response to the vibration of the fiber optic mass system. The wavelength
shift of FBG is proportional to the change in acceleration, and the gauge factor pertains to the shift in wavelength as a
function of acceleration. The accelerometer was first evaluated in laboratory settings and then employed in a
demonstration project for condition assessment of a bridge. Laboratory experiments included a series of low frequency
low amplitude sinusoidal excitation tests to evaluate the sensitivity and frequency resolution of the proposed sensor. Two
series of multiplexed FBG accelerometers were utilized to assess the dynamic properties of a bridge under ambient
vibration conditions. The Frequency Domain Decomposition method was employed to identify the mode shapes and
natural frequencies of the bridge. Results were compared with the data acquired from the conventional accelerometers.