Session 21 Max Sheppard. Improved Complex Pier Scour Prediction Procedure

Transcription

1 Session 21 Max Sheppard Ocean Engineering Associates, Inc. Improved Prediction Procedure Topic Description Improved Prediction Procedure Improvements: have been made in the methodology for predicting local scour at complex piers. In particular, the accuracy of scour depth predictions at piers with either spread footers or partially or fully buried pile caps has been improved. The revised procedure is outlined and comparisons between predicted and recently obtained laboratory data presented. Speaker Biography Max Sheppard is President of Ocean Engineering Associates, Inc. (OEA, Inc.) and Professor Emeritus in the Civil and Coastal Engineering Department at the University of Florida. His areas of expertise include: bridge scour, coastal hydraulics, sediment transport, coastal structures, and wave loading on coastal and offshore structures.

2 Session 21 Tom Glasser Ocean Engineering Associates Inc. Improved Prediction Procedure Topic Description Improved Prediction Procedure Speaker Biography Tom Glasser is a Coastal/Hydraulics Engineer at Ocean Engineering Associates Incorporated (OEA, Inc.). His areas of expertise are coastal and riverine hydraulics, sediment transport, storm surge and wave modeling, bridge scour, wave loading and design of coastal structures. Mr. Glasser received a B.S. degree in Engineering Sciences from University of Florida and a Master of Engineering degree in Coastal and Ocean Engineering from the University of Florida and has 11 years of experience.

3 Improved Prediction Procedure Complex Pier Geometries Many Bridge Piers Have Complex Geometries Methodology Presented Here Is Suitable for Piers that Can Be Approximated by the Pier Shown in the Following Figures Physical Model Studies are Recommended for Piers that Deviate Significantly from the Generic Pier 2006 Design Conference 2 1

4 Complex Pier Definition Diagram Long term scour, Channel degradation y 0 y 0 Adjusted bed Contraction scour Adjusted bed 2006 Design Conference 3 Methodology Column Top of pile cap Pile Cap y 0 = y 0 Pile Group Flow H c Complex Pier (Front View) Pier Column (Side View) + y + 0 H pc H pg y 0 Pier Pile Cap (Front View) Pier Pile Group (Front View) 2006 Design Conference 4 2

5 Complex Pier Classification Case 1 Case 2 Pile Cap Above the Bed Partially Buried Pile Cap Case 3 Buried Pile Cap Water Surface Bed Before Local Scour Sediment 2006 Design Conference 5 Methodology Effective Diameter, D*: Diameter of a water surface penetrating circular pile that will experience the same equilibrium scour depth as the structure of interest under the same sediment/flow conditions 2006 Design Conference 6 3

6 Compute the Effective Diameter, D*, of the Complex Pier where D effective diameter of the column * col * pc D = D + D + D * * * * col pc pg D effective diameter of the pile cap D effective diameter of the pile group * pg Methodology 2006 Design Conference 7 Methodology Column Column Effective Diameter, D* col D* col b col y s 2006 Design Conference 8 4

7 Methodology Pile Cap Pile Cap Effective Diameter, D* pc D* pc b col y s 2006 Design Conference 9 Methodology Pile Group Pile Group Effective Diameter, D* pg D* pg s b y s 2006 Design Conference 10 5

8 Methodology Complex Pier D * = D * col + D * pc + D * pg b col D* b col y s Sediment Sediment 2006 Design Conference 11 Effective Diameters Need to Determine, D* col, D* pc, and D* pg Using Known Structure and Flow Parameters D* = D* col + D* pc + D* pg pg, 2006 Design Conference 12 6

9 Methodology ( ) D = f b, l, y, f, f, α, H Col. Shape, * col col col col * ( 0 α ) D = f b, l, y,, f, f, T, H, D, Pile Cap Shape, * pc pc pc 1 2 pc col * * b, y 0, α, H pg, n, m, D col, D pc, s, * Dpg = f Pile Shape, Pile Array Shape 2006 Design Conference 13 Methodology Once the Effective Diameter has been Established, Equilibrium Scour Depth can be Computed Using Single Structure Scour Equations 2006 Design Conference 14 7

10 Changes From HEC-18 Methodology Additional Data Available (Including Partially Buried and Buried Pile Caps) Use of Entire Structure Effective Diameter No Adjustments to Flow Velocity Required Flow Skew Angles Accounted For in Effective Diameter Methodology Extended to Include: Partially buried pile caps Buried pile caps 2006 Design Conference 15 New Laboratory Data Tests Conducted by Max Sheppard in Hydraulics Lab at the University of Auckland Tests Conducted by Sterling Jones at FHWA Lab Tests Conducted by Stephen Coleman in Hydraulics Lab at the University of Auckland 2006 Design Conference 16 8

11 Jones Piers 2006 Design Conference 17 Existing, New and Measured Jones Case 2 and 3 Data Scour (ft) Measured FDOT HEC Experiment 2006 Design Conference 18 9

12 Sheppards Pier b col b col 1 ft b pc T 1 ft b s 0.5 ft b pc b s T 0.25 ft b col Position 1 1 ft Position 2 b b pc s T 0.1 ft Position Design Conference 19 Existing, New and Measured Sheppard s Data ys (ft) Measured Scour FDOT HEC Experiment 2006 Design Conference 20 10

13 Colemans Piers Pier 1 Pier 2 Pier Design Conference 21 Existing, New and Measured Coleman s Case 1 Data Pier 1 Pier 2 Pier 3 Scour (ft) Measured FDOT Revised HEC-18 Current Experiment 2006 Design Conference 22 11

14 Existing, New and Measured Coleman s Case 2 and 3 Data Pier 1 Pier 2 Pier 3 Scour (ft) Measured FDOT Revised HEC-18 Current Experiment 2006 Design Conference 23 FDOT Scour Program 2006 Design Conference 24 12

15 Summary Procedure Divides the Complex Pier into Its Components and Treats Each Component Separately Compute Effective Diameter of Each Pier Component (column, pile cap, pile group) Sum Effective Diameters to Obtain Effective Diameter of Entire Complex Pier Compute Scour Depth Using Single, Simple Structure Equations 2006 Design Conference 25 Summary Procedure Extended to Include Partially and Completely Buried Pile Caps Existing HEC-18 procedure can UNDER PREDICT scour depths for buried pile caps/footers 2006 Design Conference 26 13

16 Questions, Comments 2006 Design Conference 27 14