The State-ofthe-Practice of Modern Structural Health Monitoring for Bridges : A Comprehensive Review

......................................................................................................................................... iii Acknowledgements ........................................................................................................................ iii 1.0 Overview ............................................................................................................................. 1 2.0 Bridge Evaluation Process .................................................................................................. 6 2.1 Inspection Basics .......................................................................................................... 6 2.2 Visual Inspection .......................................................................................................... 7 2.3 Defects .......................................................................................................................... 7 2.4 Traditional Inspection Tools ......................................................................................... 9 2.5 Advanced Inspection Techniques ................................................................................. 9 2.6 Condition Rating......................................................................................................... 10 3.0 In-Situ Monitoring Techniques ......................................................................................... 13 3.1 Accelerometers and Velocimeters .............................................................................. 13 3.2 Electrical Resistance ................................................................................................... 14 3.3 Electromechanical Impedance .................................................................................... 15 3.4 Fiber Optics ................................................................................................................ 16 3.5 GPS and Geodetic Measurements .............................................................................. 19 3.6 Magnetic and Magneto-Elastic ................................................................................... 20 3.7 Ultrasonic Emissions and Lamb Waves ..................................................................... 22 4.0 On-Site Monitoring Techniques ....................................................................................... 25 4.1 Eddy Currents ............................................................................................................. 25 4.2 Electrical Time-Domain Reflectometry (TDR) .......................................................... 26 4.3 Infrared Thermography and Spectroscopy ................................................................. 26 4.4 Laser Scanning ........................................................................................................... 29 4.5 Nuclear Magnetic Resonance (NMR) Imaging .......................................................... 31 4.6 Microwave Radar ....................................................................................................... 33 4.7 Ground-Penetrating Radar (GPR) .............................................................................. 34 4.8 X-Ray, Gamma Ray, and Neutron Radiography ........................................................ 36 5.0 Remote Monitoring Techniques ....................................................................................... 39 5.1 Electro-Optical Imagery and Photogrammetry........................................................... 39 5.2 Speckle Photography and Speckle Pattern Interferometry ......................................... 40 5.3 Interferometric Synthetic Aperture Radar (IfSAR) .................................................... 43 6.0 Exceptional Materials and Structures ............................................................................... 45 6.1 Fiber-Reinforced Polymer Composites ...................................................................... 45 7.0 Case Studies ...................................................................................................................... 49 7.1 Commodore Barry Bridge, Philadelphia, PA ............................................................. 49 7.2 Golden Gate Bridge, San Francisco, CA .................................................................... 50