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A New Bascule Bridge:Replacement of the Alfred Cunningham Bridge in Historic New Bern

AASHTO Technical Committee MeetingMay 16, 2011

Presenter:

Eric Kelly, P.E.

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Project Location

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Existing Bridge

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• Sufficiency Rating: 8 out of 100– Structurally deficient and functionally obsolete

• Rust, corrosion, general deterioration• Inadequate sidewalk width, railing height and vertical

clearance (14-foot through truss hit by trucks)• Less than 10 years of service remaining (2005)• Maintain connectivity between James City and downtown

New Bern

Purpose and Need

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Community Context

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Structure Description

PLANControl House

Submarine Cable

• Double Leaf Trunnion Bascule• Clear Channel of 90 feet• 8 degree skew to channel• South leaf weights 1,093,000 lbs, North leaf 1,125,000

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147 feet Trunn to Trunn

ELEVATION

14’-11”High Tide El. 0.500

Structure Description

• 147 feet Trunnion to Trunnion• 71 degree angle of opening• 14’ – 11” vertical clear in closed position• Unlimited clear in channel when span

fully open

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30’ – 0”

Railing (Typ.)

2 – 11” lanes

4’ Shoulder5’ –6” Sidewalk

CROSS SECTION

Structure Description

• 2 – 11 foot travel lanes• 1 – 4 foot shoulder• 1 – 2 foot gutter• 1 - 5’ – 6” sidewalk• Classic concrete railing – each side

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Context Sensitive Structure• Structure to incorporate features of the

surroundings in Historic New Bern• Brick prevalent in town• Not practical on bridge, but color to be

highlighted

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Context Sensitive Structure

• Signature structure visible from Union Point Park

• Highlight New Convention Center at foot of bridge

• Use Terracotta Wall System• Roof to be copper that will patina in

time

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Control House

EQUIPMENT LOUVERS

STANDING SEAM COPPER HIP ROOF

WITH DEEP OVERHANGS FOR

SUN CONTROL

CONTROL ROOM(360 DEGREE

VIEWS)

ARCHITECTURAL CAST IN PLACE

CONCRETE

TERRACOTTA RAINSCREEN WALL

SYSTEM

TEXAS CLASSIC RAILING

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Control HouseFinished Product

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Control HouseFinished Product

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• Opposite pier with overlook• View of Park• Two parking facilities on approach

Unique Details

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Railing System

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Railing System

Original Structure

New Structure

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Structure Details• Concrete railing approach and bascule

spans• Increase in dead load on bascule

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Structure Details• 8” reinforced lightweight concrete deck• Improves rideability• Improves durability• Better composite action than other deck

types• Eliminates lateral bracing

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Unsymmetrical Cross Section• More complex counterweight• Monitoring transverse balance

• Railing lightweight on sidewalk• Normal weight on opposite side

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Rear Roadway Joint

PLAN

Structure DetailsRear Bascule Joint

CL Trunnion

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Rear Bascule Joint

• Reduces complex details in roadway• Better protection of machinery/trunnions

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Rear Bascule Joint

• No flanking span required• Simpler details for approach interface

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Solid Pier

• Additional protection• Cleaner appearance

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Solid Pier

Pigeons

• Additional protection

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Structure Details

• Welded Plate Bascule Girder/Floorbeams

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Structure Details

Counterweight

98’ – 0” Overall Length

Girder 10’ -1 1/2” maximum depthFlanges 24” Wide

1.75” to 2.25” Thick

Welded Plate Bascule Girder/Floorbeams• Detailed to Designer requirements• More costly, but more efficient

24’ – 6”

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Structure Details

Machinery Platform Limit

Counterweight Limitat Trunnion Column

• Tight Clearances• 3 dimensional

Clearance to pit floor

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Structure Details

• Counterweight to Pit Floor

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Structure Details

• Counterweight to Trunnion Column

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Structure Details

• Clearances

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Structure Details

• Clearances

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Structure DetailsSteel Trunnion Columns

• Improved alignment capabilities• More compact section for support

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Machinery/Structure Details

CL Bascule Girder

5’-4”

TrunnionTrunnion

Trunnion Hub connection to Bascule Girder• Simpler Trunnion – one piece• Stiffening of Girder• Facilitates installation• Epoxy for contact• Line bore for alignment

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Machinery Details • Bronze bushed Trunnion

• Less costly than roller bearings• Simplify trunnion details

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Operating Machinery

PLAN

30’ – 0”

8’- 4”

SIDE VIEW

Trunnion

Rack Pinion

• Rack pinion gear drive• Utilizes fully enclosed reducers• 50 HP motor main drive• 70 seconds to full open

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Machinery Details

• Compact design• Auxiliary motor• 2 speed motor

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Machinery Details• Common Supports• Reduce field alignment

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Machinery Details

Mill Plate between Rack and Bascule Girder

Mill Plate• Facilitates installation• Simplifies girder fabrication• Prevents costly rework

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Electrical Details

Follow 2’s Rule• Two sources of power

• Primary• Generator

• Two sources of control• PLC• Relay

• Two sources of drive• Main motor• Auxiliary motor

Electrical System provides reliable service through redundant systems

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Electrical DetailsMain Drive – DC motor• Proven reliable system• Provides good operating characteristics in varying

load conditions• Excellent speed control

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Electrical Details• PLC – Programmable Logic Controller• State of the Art electronics for monitoring and control of bridge

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QUESTIONS & ANSWERS