Hydraulic Design of New Woodrow Wilson Bridge

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Hydraulic Design of New Woodrow Wilson Bridge
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Hydraulic Design of New WWB
Location of Woodrow Wilson Bridge
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Hydraulic Design of New WWB

• WWB bridge carries I-95 I-495 over Potomac R.
• Opened in 1961
• Designed for 75,000 VPD
• Today gt190,000VPD
• 300,000 VPD by 2020
• Owned by FHWA
• Located in VA, DC and MD

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Hydraulic Design of New WWB

• Existing bridge 5,900 ft long
• 58 spans
• Four leaf bascule span
• Functionally obsolete
• Deck on Bascule Spans beyond fatigue life
• New bridge under design

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Hydraulic Design of New WWB

• New bridge 6052 ft long
• 2 parallel bridges
• 18 spans
• 8 leaf bascule span
• Pile supported footings
• Capacity 300,000 VPD
• Estimated cost 2B

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Hydraulic Design Process Concepts Worth
Discussing

• Scour Team
• Organization Coordination
• Hydrology
• Computer Models
• Physical Models
• Scour in Cohesive Soils
• Final Recommendations

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The Scour Team
Final recommended scour depths and pier geometry
were determined by a team of hydraulic,
structural and geotechnical engineers .
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The Scour Team

• Represents a wide area of knowledge and
  experience
• Provides opportunity to apply state-of -the-art
  methodologies
• Provides opportunity for periodic review and
  discussion of different methodologies
• Team serves as decision maker for complex issues
  or where there is a divergence of viewpoints

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Hydraulic Design of New WWB Coordination
Communication

• General Engineering Consultant/Subs
• Design Consultant/Subs
• FHWA and State DOTs
• University and other Research Engineers
• Structural Concerns
• Geotechnical Concerns
• Hydraulic / Scour Concerns
• Coordination Communication of Decisions

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PIER DESIGN PROCESS
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Hydrologic Design of New WWB

• HYDROLOGY
• Drainage area at bridge site 11,860 sq. mi.
• Tidal influence at bridge, 3 ft range day
• Q100 480,000 cfs
• Q500 700,000 cfs

Potomac River Basin
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Hydraulic Design of New WWB

• HEC-RAS Analysis performed for Q100 and Q500
• 10 Cross sections surveyed
• Boundary conditions defined by flood records
• n based on previous calibration study by Corps
  of Engineers

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Hydraulic Design of New WWB

• Tidal analysis of river performed for Q100 and
  Q500 using Maryland Tidal Analysis Program
  (based on the Neill method) and studies by the
  University of Maryland.

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Hydraulic Design of New WWB
Local velocities for scour analysis determined by
conveyance subdivision.
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Hydraulic Design of New WWB
Modeling of Energy Losses at Piers. Wide piers
modeled as blocked obstructions
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Hydraulic Design of New WWB

• SMS-Flo2DH Analysis performed for Q100 and Q500
• Ground River elevations from 30 m DEMs and
  Estuary database
• n adjusted to match 1-D upstream WS Elevation

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Hydraulic Design of New WWB
Local velocities and angle of attack for scour
analysis obtained directly from 2-D output.
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Hydraulic Design of New WWBScour Analysis

• HEC-18 with wide pier modification (using local
  velocities from 1-D 2-D Models )
• FHWA Equations for complex piers
• Enhanced CCHE 3-D Model
• Physical Models (large and small scale)
• Scour in cohesive materials
• Abutment Scour
• Vertical and Lateral Stream Stability
• Risk Assessment

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Hydraulic Design of New WWBRiver Stability

• Bridge Inspection Records
• Corps of Engineers records of work on the river
• Application of Corps of Engineers (Maynord)
  method for evaluation of bend scour
• Long term records available on the Internet

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Hydraulic Design of New WWB

• Enhanced CCHE3-D Model with fully coupled
  sediment transport used to analyze main piers for
  various flow conditions
• Used to quantify shear stress in scour holes for
  SCRICOS Stream Power/ Erodibility Index methods

3-D simulation of tidal flow before old bridge
demolished
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Hydraulic Design of New WWB
A select number of large scale tests were
conducted at the USGS lab in Turners Falls ,MA
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Hydraulic Design of New WWB
Many small scale physical model tests were
performed at FHWAs TFHRC Lab
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PIER DESIGN PROCESS
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Q100 Scour Dolphins Scour 63 ft. at Dolphin
55 ft. at pier
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Q100 Scour Fender RingScour 30 ft. at ring 29
ft. at pier
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Hydraulic Design of New WWBScour in Cohesive
Materials
Erosion rate tests were conducted using the EFA
apparatus under development at Texas AM
University
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Hydraulic Design of New WWBScour in Cohesive
Soils
Estimates of pier scour were provided by Dr. J.
L. Briaud using the SRICOS method he has
developed
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Hydraulic Design of New WWB Scour in Cohesive
Soils
Estimates of scour depth were provided by Dr.
George Annandale of Golder Associates, Colorado
using Stream power/ Erodibility Index Method
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Methodologies used in Hydraulic Analysis

• HEC-RAS
• Maryland SHA (Neill ) Tidal Analysis
• 2-D Analysis
• 3-D Analysis

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Methodologies used in Scour Analysis

• HEC-18 Equations
• Wide pier scour equation
• Salim-Jones Jones-Sheppard pier scour equations
• Sheppard pier scour equation
• Enhanced CCHE 3-D Model
• Hydraulic Laboratory Tests- large scale and small
  scale
• Erodibility Index Method - cohesive soils
• SRICOS Method - cohesive soils

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The Scour Team
Final recommended scour depths and pier geometry
were determined by a team of hydraulic,
structural and geotechnical engineers.
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Any Questions?