Monitoring Scour Critical Bridges (2009) / Chapter Skim
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SYNTHESIS OF PRACTICES The use of fixed instrumentation as a scour countermeasure is a process that begins with the evaluation of the scour countermeasure alternatives for a particular bridge site, includes the design and installation of the instrumentation and the development of a scour monitoring program, and can continue for many years with the scour monitoring program for the bridge. Owners and others that have completed the synthesis surveys have reported successes and failures at various steps of the process.
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54 • Water depth, • Bed material, and • Extreme conditions. The functional applications and bridge geometry include information on the characteristics of the bridges for the different types of instruments: (1)
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TABLE 8 FIXED INSTRUMENTATION SELECTION MATRIX (Countermeasure characteristics) Local Scour Contraction Flow Habit Water Depth Bed Material Extreme Conditions Foundation Type Maintenance Type of Fixed Abutments 1 Piers Scour Vertical Lateral Tidal Riverine E=Ephemeral A = < 3 ft F = Fine bed D=Debris P=Piles Continuous Remote H = High No.
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From page 56... ...
future repair costs, especially on bridges over deep waters. This is the result of the high costs associated with underwater installations, maintenance, and repairs.
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From page 57... ...
Because the construction inspector cannot view the underwater components, it is advisable to have these components of the installation inspected by an independent contractor before completion of the contract. This will ensure that all bolts and attachments are in place and that the mounting is properly secured to the substructure unit.
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58 A clear chain of command of those responsible for emergency situations needs to be in place. Those responsible for analyzing the data should have instructions as to who they should contact "round-the-clock" should the scour readings indicate a problem.
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59 and one site had both sonar and collar installations. In the case of bridges over tidal waterways, the worst scour can be on the ebb or the flood tide of the bridge.
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60 FHWA LTBP The FHWA initiated a major program in early 2006 with the objective of improving knowledge regarding bridge performance over a long period of time. The FHWA LTBP program will instrument, monitor, and evaluate a large number of bridges throughout the United States to capture performance data over a 20-year period of time and, on the basis of the information collected from these structures, provide significantly improved life-cycle cost and performance and predictive models that can be used for bridge and assetmanagement decision making.
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From page 61... ...
61 Rivers, and the new Tacoma Narrows Bridge in Tacoma, Washington. Consideration could also be given to structural bridge health monitoring.
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