2013 Louisiana Transportation Conference

Transcription

1 2013 Louisiana Transportation Conference

2 Background FHWA/AASHTO study Objectives of LADOTD study Level III methodology Surge/Wave force methodology 100-Year Surge-Wave GIS Atlas Summary Questions

3 Pensacola, FL Bay Saint Louis, MS Biloxi, MS Biloxi, MS

4 I10 Bridges over Lake Pontchartrain New Orleans, LA

5 Study objectives: Develop methods for predicting surge/wave loads on bridge superstructures Result: AASHTO Guide Specification for Bridges Vulnerable to Coastal Storms Outlined 3 levels of analysis Developed wave force equations

6 Hindcast all major tropical storms and hurricanes that have impacted the area Perform extreme value analyses on the met/ocean parameters (water elevation, wave heights, depth-averaged currents) at each node Use this information to compute the design surge/wave loads on selected bridges Estimate bridges vulnerability to these loads

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8 Study objectives: Perform a Level III analysis to determine the vulnerability of a selected number of LADOTD coastal bridges to design surge/wave loading Create a storm surge/wave atlas for Louisiana Coastal Waters

9 Design: Storm water level Water depth Wave height and period Bridge superstructure parameters Span type and dimensions Low chord elevation Force prediction equations Obtained by Level III storm hindcasts and extreme value analyses Provided by LADOTD

10 Selection of storms to hindcast Obtain wind velocity & atmospheric pressure Develop surge/wave model mesh Acquire model calibration data Debug - calibrate models Run surge/wave models Extract pertinent information from model results

11 Selected Storms Paths of Storms that Occurred Before 1920

12 Selected Storms Paths of Storms that Occurred After 1920

13 Hindcast Procedure

14 Model Mesh Mesh defines topography/bathymetry Mesh consists of triangular elements defined by nodes at each corner Developed using an algorithm that relates mesh element size to both local bed elevation and local bed gradient Modified to include detail of the Louisiana coastal region Mesh contains more than 620,000 nodes Topography an bathymetry provided by multiple sources

15 Model Mesh ADCIRC + SWAN Mesh

16 Model Mesh ADCIRC + SWAN Mesh

17 Model Mesh (cont.) Location of Detailed Regions of the Mesh

18 Model Calibration Iterative processes of adjusting model parameters until model results match measured results within acceptable limits FEMA defines the acceptable limit as; 10% or less for tidal calibrations greater under storm conditions due to complexity For ADCIRC calibration model parameters are bottom friction and lateral eddy viscosity For SWAN calibration model parameters are bottom friction, white capping and breaking criteria

19 Model Calibration Data ADCIRC Water surface elevations High water marks SWAN Wave height

20 ADCIRC Model Calibration Data

21 ADCIRC Model Calibration Results

22 SWAN Model Calibration Data

23 SWAN Model Calibration Results

24 Tropical Storms & Hurricanes to be Hindcasted Storms that Occurred Before 1920 Storm Year Not Named 1852 Not Named 1855 Not Named 1856 Not Named 1860 Not Named 1860 Not Named 1860 Not Named 1865 Not Named 1867 Not Named 1879 Not Named 1879 Not Named 1882 Not Named 1886 Not Named 1886 Not Named 1888 Not Named 1893 Not Named 1893 Not Named 1897 Not Named 1900 Not Named 1906 Not Named 1909 Not Named 1915 Not Named 1915 Not Named 1916 Not Named 1917 Not Named 1918 Storms that Occurred After 1920 Storm Year Not Named 1926 Not Named 1932 Not Named 1940 Not Named 1943 Not Named 1947 Not Named 1949 AUDREY 1957 ETHEL 1960 HILDA 1964 BETSY 1965 CAMILLE 1969 EDITH 1971 CARMEN 1974 FREDERIC 1979 DANNY 1985 ELENA 1985 JUAN 1985 ANDREW 1992 GEORGES 1998 LILI 2002 KATRINA 2005 RITA 2005 HUMBERTO 2007 GUSTAV 2008 IKE 2008

25 Example Hurricane Hindcast Hurricane Katrina Wind Fields

26 Example Hurricane Hindcast Hurricane Katrina Wind Fields

27 Example Hurricane Hindcast Hurricane Katrina Wind Fields

28 Example Hurricane Hindcast Hurricane Katrina Wind Fields

29 Example Hurricane Hindcast Hurricane Katrina Wind Fields

30 Example Hurricane Hindcast Hurricane Katrina Wind Fields

31 Example Hurricane Hindcast Hurricane Katrina Wind Fields

32 Example Hurricane Hindcast Hurricane Katrina Wind Fields

33 Example Hurricane Hindcast Hurricane Katrina Wind Fields

34 Example Hurricane Hindcast Hurricane Katrina Wind Fields

35 Example Hurricane Hindcast Hurricane Katrina Wind Fields

36 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

37 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

38 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

39 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

40 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

41 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

42 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

43 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

44 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

45 Example Hurricane Hindcast Hurricane Katrina Water Surface Elevations

46 Storm Surge/Wave Force F F + F + F + F H Slaming Drag Inertia CAM F = F + F + F + F + F V Slaming Buoyancy Drag Inertia CAM

47 Storm Surge/Wave Force (cont.) Vertical Force on Slab Superstructure

48 Storm Surge/Wave Force (cont.) Vertical Force on Girder Superstructure

49 Storm Surge/Wave Force (cont.) Vertical Force on Submerged Superstructure

50 Level III procedure produces significant information beyond that needed for surge/wave loads on bridges 100-Year water level, flow, and wave information at each of the approximately 620,000 nodes in the model mesh This information has numerous uses, e.g. Design scour depths at existing and new bridges Designing erosion/scour protection at bridge abutments Designing scour protection for coastal roadways Identifying vulnerable sections of roadways on evacuation routes, etc.

51 GIS Database being developed as part of this study Includes: 100-Year Met/Ocean conditions Surge/Wave loading on selected coastal bridges Bridge information for analyzed coastal bridges

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