Development of Methods for Improving Levels I and II Met/Ocean Parameter Predictions

摘要

The prediction of storm surge and wave forces and moments on bridges requires knowledge of design (100-year) water levels and wave heights and periods (met/ocean conditions) as well as bridge dimensions, elevation, orientation, etc. The American Association of State Highway and Transportation Officials (AASHTO) code, Guide Specification for Bridges Vulnerable to Coastal Storms, describes three levels of analysis (Levels I, II and III) for obtaining the met/ocean conditions. By necessity Levels I and II analyses over-estimate the combined water levels and wave heights. The objective of this study was to develop a method for adjusting Level I results to bring them more in line with those from a Level III analysis while maintaining a reasonable level of over prediction. Data and information obtained in an FDOT sponsored Pilot Study in the Tampa-Saint Petersburg, Florida area, where Levels I, II and III analyses were performed, were used in the development of Level I modifiers for both design water level and wave heights. The modifiers are in terms of readily available water basin geometric parameters. Extracting this information does, however, require some level of understanding of coastal hydraulics/processes and should be performed by someone knowledgeable in this area. The modified results will retain a degree of over-prediction provided the rules for application of the modifiers, outlined in the report, are followed.