Risk Analysis of Bridges to Prioritize Post-Storm Scour Mitigation Plans

Transcription

1 Risk Analysis of Bridges to Prioritize Post-Storm Scour Mitigation Plans Samaneh GHOLITABAR Elham AZIMI Fletcher H. GRIFFIS May 31- June 2, 2016

2 Outline Introduction Objectives Methodology Conclusion

3 Introduction Hydraulic failures (scour failure) are accounted of 60 % of all reported failures Scouring is the erosion of soil around bridge piers due to water flow Factors that affect scouring : bed materials, bridge geometry, channel protection measures, and flow hydraulics The outcome of this work can assist authorities in understanding the risk of bridges scouring for its region

4 Objectives The three main objectives : 1) Develop a framework for evaluating risk of potential scour for the community 2) Extracting various types of data from different resources and databases and integrate them into the developed risk evaluation framework 3) Identification of scour susceptible bridges and the associated level of risk

5 Methodology Risk-based methodologies has been used for bridge management under extreme events Considerable researches in the past to quantifying scour hole depth Present study: prioritizing of bridges requiring scour remediation. Extracting various types of data from different resources and databases including GIS based data, integrate them into the developed risk evaluation framework The outcome of this work can assist authorities in understanding the scouring risk of bridges.

6 Methodology-Risk Assessment tool Risk = Hazard Exposure Vulnerability Hazard: The 100-year storm was adopted in this study, which is the maximum probable storm that can occurs over a 100 year period AEP = 1 e ( 1 Return period ) Liklihood = 1 (1 AEP) N Hazard Score Description 5 Highly unlikely, but conceivable. Extreme intensity event. 4 Unlikely to occur. Very high intensity event 3 About as likely as not (possible). High intensity event. 2 Likely to occur. Moderate intensity event. 1 Very likely or expected to occur. Low intensity event. Probability of occurrence within planning 1-10% probability of occurring 10-33% 33-66% 66-90% >90%

7 Methodology-Risk Assessment tool Risk = Hazard Exposure Vulnerability Exposure: Effect of topographic and shoreline features that can affect severity of damage as well as community rank. Three factors in calculating the exposure score the scores from each of the mentioned factors were added to obtain a final exposure score 1) location of the bridge with respect to flood prone zones (Score: 0-1) 2) landscape attributes included (Score: 0-3) a)erosion rate, b) Channel protection, c) Land cover, d) Dune or bluff, e) Soils type, f) Scour condition 3) Income and population of the community affected by the bridge (Score: 0-1) (GIS- Spatial Analysis).

8 Methodology-Risk Assessment tool Risk = Hazard Exposure Vulnerability Vulnerability: level of impairment or consequences that assets may experience from a storm event. Vulnerability score was evaluated based on (GIS-Spatial Analysis) (a) Bridge characteristics (b) Proximity of primary and secondary roads to a bridge (c) Proximity to railroad service

9 Methodology-Risk Assessment tool Risk = Hazard Exposure Vulnerability Vulnerability: Vulnerability score was evaluated based on (GIS-Spatial Analysis)

10 Result A total of 95 bridges were evaluated The scores from each category were first derived from the GISbased maps, then transferred to tabular formats. The risk score for each bridge was calculated based on Methodology. Comparing the risk score with the reference table of risk score Eight bridges out of 95 were found to have a high risk. Table 3. Reference table for Risk score NY state risk assessment inventory reference table Exposure 100-year event (Hazard score = 3) Vulnerability

11 Conclusion The method allows for calculation of risk, based on vulnerability, exposure and hazard levels. The methodology was applied GIS analysis for evaluating different parameters of risk. The developed methodology allows for prioritization in allocation of limited funding for bridge scour mitigation. The methodology saves time and money for decision making process.

12 References Yao, C., Briaud, J. L., & Gardoni, P. (2015, March). Risk Analysis on Bridge Scour Failure. In IFCEE Ho, C. L., Di Stasi, J. M., & Rees, P. (2002). GIS-Based bridge scour prioritization. In Proceedings of the First International Conference on Scour of Foundations, ICSF (Vol. 1, No. 2, pp ). Wang, Y. M., & Elhag, T. M. (2007). A fuzzy group decision making approach for bridge risk assessment. Computers & Industrial Engineering, 53(1), Johansson, C., Nualláin, N. N., Pacoste, C., & Andersson, A. (2014). A methodology for the preliminary assessment of existing railway bridges for high-speed traffic. Engineering structures, 58, Govindasamy, A. V. (2009). Simplified method for estimating future scour depth at existing bridges (Doctoral dissertation, Texas A&M University). Slovinsky, P Maine Coastal Property Owner s Guide to Erosion, Flooding, and Other Hazards (MSG-TR-11-01). Orono, ME: Maine Sea Grant College Program.

13 Thank You