University of Florida Civil and Coastal Engineering Final Report April 2016 Structures Research Report 2016/00112484- 00112485 Determination of Barge Impact Probabilities for Bridge Design Principal investigator: Gary R. Consolazio, Ph.D. Research assistant: George C. Kantrales Department of Civil and Coastal Engineering University of Florida P.O. Box 116580 Gainesville, Florida 32611 Sponsor: Florida Department of Transportation (FDOT) William Potter, P.E. – Project manager Contract: UF Project No. 00112484 & 00112485 FDOT Contract No. BDV31-977-21 University of Florida University of Florida Civil and Coastal Engineering DISCLAIMER The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Florida Department of Transportation or the U.S. Department of Transportation. ii SI (MODERN METRIC) CONVERSION FACTORS APPROXIMATE CONVERSIONS TO SI UNITS SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL LENGTH in inches 25.4 millimeters mm ft feet 0.305 meters m yd yards 0.914 meters m mi miles 1.61 kilometers km AREA in2 square inches 645.2 square millimeters mm2 ft2 square feet 0.093 square meters m2 yd2 square yard 0.836 square meters m2 ac acres 0.405 hectares ha mi2 square miles 2.59 square kilometers km2 VOLUME fl oz fluid ounces 29.57 milliliters mL gal gallons 3.785 liters L ft3 cubic feet 0.028 cubic meters m3 yd3 cubic yards 0.765 cubic meters m3 NOTE: volumes greater than 1000 L shall be shown in m3 MASS oz ounces 28.35 grams g lb pounds 0.454 kilograms kg T short tons (2000 lb) 0.907 Megagrams Mg (or "t") TEMPERATURE (exact degrees) oF Fahrenheit 5(F-32)/9 or (F-32)/1.8 Celsius oC ILLUMINATION fc foot-candles 10.76 lux lx fl foot-Lamberts 3.426 candela/m2 cd/m2 FORCE and PRESSURE or STRESS kip 1000 pounds force 4.45 kilonewtons kN lbf pounds force 4.45 newtons N lbf/in2 pounds force per square inch 6.89 kilopascals kPa psf pounds force per square foot 47.88 pascals Pa iii Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle 5. Report Date April 2016 Determination of Barge Impact Probabilities for Bridge Design 6. Performing Organization Code 8. Performing Organization Report No. 7. Author(s) G. R. Consolazio, G.C. Kantrales 2016/112484-112485 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) University of Florida Department of Civil & Coastal Engineering 11. Contract or Grant No. P.O. Box 116580 BDV31-977-21 Gainesville, FL 32611-6580 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Florida Department of Transportation Final Report Research Management Center 605 Suwannee Street, MS 30 14. Sponsoring Agency Code Tallahassee, FL 32301-8064 15. Supplementary Notes 16. Abstract Waterway bridges in the United States are designed to resist vessel collision loads according to design provisions released by the American Association of State Highway and Transportation Officials (AASHTO). These provisions provide detailed procedures for calculating design vessel impact loads within the context of a comprehensive risk assessment. One of the primary subcomponents of this process is the calculation of probabilities that estimate the likelihood that a barge-to-bridge impact event will occur. However, the expressions used to predict the frequency of barge-to-bridge collisions were developed from a limited number of data sets. Furthermore, the technology employed by the maritime industry at the time the original AASHTO provisions were developed—in the early 1990s—has been significantly improved in subsequent decades. As a consequence of these factors, current estimates of barge-to-bridge collision probabilities may differ from presently-employed AASHTO estimates. The focus of the research described in this report was the development of a revised barge impact probability expression particularly applicable for the design of bridge structures located on Florida waterways. Specifically, the existing AASHTO expression for the base aberrancy rate (BR)—used to estimate the likelihood that a barge flotilla will stray from the intended transit path—was recalibrated and updated. Barge flotilla traffic data and barge-to-bridge collision (casualty) data for Florida bridge locations were collected and used to compute historical barge-to-bridge collision probabilities. These probabilities were then utilized in conjunction with additional supplementary parameters specified in AASHTO—quantified using bridge site-specific information—to back-calculate BR values for each bridge location. A subset of BR estimates from several bridge sites were then utilized to produce a single design value of BR that may be used in risk assessments for new and existing bridge structures. Based on results from the recalibration process, the updated BR estimate was 55% smaller than the current value prescribed by AASHTO. To demonstrate the effect of the recalibrated BR parameter, annual frequency (AF) of collapse values from risk assessments of two previously-investigated bridge structures—the Bryant Grady Patton Bridge (Apalachicola Bay, FL) and the LA-1 Bridge (Leeville, LA)—were recomputed using the updated BR expression. Despite the reduction in BR, values of AF estimated using UF/FDOT methods and the updated BR expression remained high relative to AF estimates produced by existing AASHTO methods. It was noted in this study that bridge locations with low volumes of barge traffic corresponded to high estimates of BR. This finding was a consequence of utilizing less data in the statistical calibration process, which reduced the accuracy of the resulting predictions. Consequently, only Florida bridge locations with significant levels of barge flotilla traffic were utilized to produce the recommended design value of BR. However, additional out-of-state locations exist with more highly trafficked bridge locations, as well as a more comprehensive source of barge traffic data. Inclusion of such locations in a similar recalibration effort could result in a lower design value of BR. 17. Key Words 18. Distribution Statement Barge, impact, collision, bridge pier, risk assessment, probability of No restrictions. impact, aberrancy rate, bridge design specifications 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 119 Form DOT F 1700.7 (8-72). Reproduction of completed page authorized iv ACKNOWLEDGEMENTS The authors thank the Florida Department of Transportation (FDOT) for providing the funding that made this research project possible. The authors also thank the United States Coast Guard (USCG) and the United States Army Corps of Engineers (USACE) for providing the data necessary to complete this work. Specific thanks are extended to Ms. Amy Tujague (USACE Waterborne Commerce Statistics Center), Capt. Timothy McGill (St. Johns Bar Pilot Association), Capt. Gary Bryan, and Capt. Clyde Wolfe for their individual contributions. v EXECUTIVE SUMMARY Waterway bridges in the United States are designed to resist vessel collision loads according to design provisions released by the American Association of State Highway and Transportation Officials (AASHTO). These provisions provide detailed procedures for calculating design vessel impact loads within the context of a comprehensive risk assessment. One of the primary subcomponents of this process is the calculation of probabilities that estimate the likelihood that a barge-to-bridge impact event will occur. However, the expressions used to predict the frequency of barge-to-bridge collisions were developed from a limited number of data sets. Furthermore, the technology employed by the maritime industry at the time the original AASHTO provisions were developed—in the early 1990s—has been significantly improved in subsequent decades. As a consequence of these factors, current estimates of barge-to-bridge collision probabilities may differ from presently-employed AASHTO estimates. The focus of the research described in this report was the development of a revised barge impact probability expression particularly applicable for the design of bridge structures located on Florida waterways. Specifically, the existing AASHTO expression for the base aberrancy rate (BR)—used to estimate the likelihood that a barge flotilla will stray from the intended transit path—was recalibrated and updated. Barge flotilla traffic data and barge-to-bridge collision (casualty) data for Florida bridge locations were collected and used to compute historical barge- to-bridge collision probabilities. These probabilities were then utilized in conjunction with additional supplementary parameters specified in AASHTO—quantified using bridge site- specific information—to back-calculate BR values for each bridge location. A subset of BR estimates from several bridge sites were then utilized to produce a single design value of BR that may be used in risk assessments for new and existing bridge structures. Based on results from the recalibration process, the updated BR estimate was 55% smaller than the current value prescribed by AASHTO. To demonstrate the effect of the recalibrated BR parameter, annual frequency (AF) of collapse values from risk assessments of two previously-investigated bridge structures—the Bryant Grady Patton Bridge (Apalachicola Bay, FL) and the LA-1 Bridge (Leeville, LA)—were recomputed using the updated BR expression. Despite the reduction in BR, values of AF estimated using UF/FDOT methods