Risk-Based Inspection and Strength Evaluation of Suspension Bridge Main Cable Systems (2023) / Chapter Skim
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Pages 91-98
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From page 91... ...
91 C H A P T E R 6 Review of NDE/SHM Methods General Discussion A variety of NDE technologies has been considered in this investigation. The primary challenge is finding technologies and sensors that are suitable for applications on main cables of suspension bridges taking into consideration the limitations imposed by working a few hundred feet above the roadway, with limited or no traffic disruption, in harsh environments, and with limited power sources.
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From page 92... ...
92 variations in the cable's cross-section, providing information on the loss of cross-sectional area induced by the corrosion process. No information on cracked wires and on the distribution of the different corrosion stages will be provided.
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From page 93... ...
93 The limitations of this technology for successful suspension bridge main cable applications are multiple, and are mainly linked to the size of the cable to inspect and to the logistics of running such a test in the field. First of all, in order to be picked up by the sensor, the reduction of the cable's crosssection must extend over the entire length of the magnetic field sensor (almost the entire length of the magnet)
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From page 94... ...
94 relatively large number of wires, the increase in attenuation and loss of the signal is due to transmission of the wave energy into adjacent wire bundles, resulting in energy loss from the main pulse. However, although the inability to deal with main cables, magnetostrictive technologies are currently used in assessing the conditions of vertical suspender ropes and of wire strands at anchorages.
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From page 95... ...
95 position and distance between the sensor(s) and the crack opening, the type of material, the interference with other components, etc.
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From page 96... ...
96 damaged area and thus the characteristics of the signal propagating along the rope. In this way, an array of AE sensors will serve as continuous online monitoring detectors of wire breaks or other type of damage and help evaluating the damage in combination with the MS component.
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From page 97... ...
97 embedded, through cable wedging, in a panel of the main cable of the Manhattan Bridge in NY and measurements were collected for almost one year. In Figure 36, the measurements of the temperature and relative humidity recorded at one sensor in one of the cables of the Manhattan bridge are shown for three different days (January 23, March 12 and August 1, 2011)
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From page 98... ...
98 known that there is a correlation between humidity and ferrous corrosion. In the case of main cables, dehumidification is accomplished by injecting dry air into the interior of the cable and by removing humid air from the cable at some injection ports along the cable length.
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