Wabash Bridge Competition Bridge...
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Wabash Bridge Competition Bridge Engineering Todd Wilson, B.S., E.I.T. Traffic Engineer - DMJM Harris
Transcript of Wabash Bridge Competition Bridge...
Wabash Bridge Competition
Bridge Engineering
Todd Wilson, B.S., E.I.T.Traffic Engineer - DMJM Harris
In 1904, the Wabash Bridge opened to carry the Wabash-Pittsburg Terminal Railroad over the Monongahela River. In
1948, the bridge was removed. The piers still remain.
Now it is up to you to design a pedestrian bridge or structure to bring new life to the old abandoned bridge piers.
Overview
• Definitions• Engineering
– Forces– Type– Configuration– Form
• Classification Challenge• Other Design Considerations
Definitions
• Abutment - support at beginning or end ofbridge integrated with the ground
• Pier - intermediate support• Span - the bridge between two supports• Girder - a tall, narrow beam• Support Structure - the part of the bridge
that carries the load
Engineering - Classification of Forces
• Function of bridge: to carry a load across adistance
• Due to gravity, all loads have a downwardforce (weight)
• All bridges can be classified into thefollowing basic types based on how theycarry the weight:– Compression– Tension– Tension/Compression (Both)
Compression Bridges
• Compression is the “push” force• Compression causes an object to get shorter• Stone and concrete are strong in
compression
Compression Bridges - Arch• A bridge that supports a weight in compression is
an arch bridge• The circular arc in compression supports the road• The arch can be below the road or above the road
Compression Bridge - Arch
Photo: Todd Wilson
Tension Bridges
• Tension is a “pull” force• Tension causes an object to get longer• Wire rope and chains are strong in tension
Tension Bridge - Suspension• A suspension bridge features a long cable strung
over towers and anchored on both sides• Smaller cables are hung from the main cables and
connect to the road deck• The cables in tension support the road
Tension Bridge - Suspension
Photo: Todd Wilson
Tension Bridge - Cable Stayed• A cable stayed bridge features cables that connect
directly from a tower to the road• The cables in tension support the road
Tension Bridge - Cable Stayed
Photo: Todd Wilson
Tension/Compression Bridge
• A beam bends under the weight of a load• When the beam bends, the top half is in
compression and the bottom half is in tension• The taller the beam, the stronger it is
A Beam Bridge…
Now let’s add vertical rods to help you see whatis going on. They serve no structural purpose.
The top rods are pushed together incompression
The bottom rods are pulled apart in tension
Tension/Compression - BeamPhoto: Todd Wilson
Tension/Compression - Truss
•As a beam gets taller and taller, itbecomes too costly and too heavy
•Solution: build a truss•Trusses have the same function as
beams, but are composed of triangles
Tension/Compression - Truss– Top composed of thick beams (compression)– Bottom composed of thin eye-bar chains (tension)
Photo: Todd Wilson
Truss Types
• Bowstring• Lenticular• Pratt• Double Intersection
Pratt (Whipple)• Baltimore• Parker
• Pennsylvania• Warren• Double Intersection
Warren• Warren Quadrangular
(Lattice)• K Truss
Truss Type - Bowstring
Photo: Todd Wilson
Truss Type - Lenticular
Photo: Todd Wilson
Truss Type - Pratt
Photo: Todd Wilson
Truss Type - Double Intersection Pratt
Photo: Todd Wilson
Truss Type - Baltimore
Photo: Todd Wilson
Truss Type - Parker
Photo: Todd Wilson
Truss Type - Pennsylvania
Photo: Todd Wilson
Truss Type - Warren
Photo: Todd Wilson
Truss Type - Warren
Photo: Todd Wilson
Truss Type - Warren
Photo: Todd Wilson
Truss Type - Warren
Photo: Todd Wilson
Truss Type - Double Intersection Warren
Photo: Todd Wilson
Truss Type - Warren Quadrangular
Photo: Todd Wilson
Truss Type - K
Photo: Todd Wilson
Tension/Compression Configurations
• Simple– Beam or truss rests on one support on each end
• Continuous– Beam or truss continues over at least one support
between the end supports• Cantilever
– One (or both) ends of a beam or truss are projectedpast the end of a support - the projected anchor spans
– A subsequent beam or truss is connected to theprojected spans - the suspended span
Configuration - Simple
Photo: Todd Wilson
Configuration - Simple
Photo: Todd Wilson
Configuration - ContinuousPhoto: Todd Wilson
Configuration - Continuous
Photo: Todd Wilson
Configuration - Cantilever
Photo: Todd Wilson
Configuration - Cantilever
Photo: Todd Wilson
Configuration - Cantilever
Photo: Todd Wilson
Bending - Simple• A simple bridge bends the most at the midpoint
between supports• Simple bridges are often thickest in center
Photo: Todd Wilson
Bending - Continuous• An intermediate support causes bending• A continuous structure becomes thicker over a pier
Photo: Todd Wilson
Bending - Cantilever• Each projected span bends over a pier• Weight of suspended span applies a weight to the
ends of the projected spans• This also causes bending• Cantilevers are thickest over pier to resist bending
Photo: Todd Wilson
Classification of Form
• Bridges are classified based on location ofstructure relative to the road (deck)– Deck: (structure beneath road)– Pony: (structure next to, but not above road)– Through: (structure above road)– Half Through (structure above and below road)
Classification of Form - Deck
Photo: Todd Wilson
Classification of Form - Pony
Photo: Todd Wilson
Classification of Form - Through
Photo: Todd Wilson
Classification of Form - Half Through
Photo: Todd Wilson
Classification Challenge
• For each bridge, try to classify it!• Use the following categories:
– Form: deck, pony, through, half through– Type: tension, compression, tension/compression– Style: arch, suspension, cable stayed, beam,
truss– Beam Configuration (if applicable): deck, pony,
through, half through• Note: Some bridges will be combinations of
styles we discussed
Cable Stayed
Photo: Todd Wilson
Simple Through Truss
Photo: Todd Wilson
Continuous Deck Girder (Beam)
Photo: Todd Wilson
SuspensionPhoto: Todd Wilson
Cantilever Through Truss
Cantilever Deck Truss
Photo: Todd Wilson
Cantilever Through Truss & Arch
Photo: Todd Wilson
Through ArchPhoto: Todd Wilson
Tied ArchPhoto: Todd Wilson
Materials
• Steel– Weathering– Galvanized
• Iron• Wire Rope• Wood• Concrete• Reinforced Concrete• Masonry (stone)
More Design Considerations
ß Impact on area– Traffic– Railroad– Pedestrian
• Implementability• Signage• Lighting
• Marketing• Maintenance• Security/Crime• Size• Liability (Lawsuits)• Clearance• Attractiveness
ADA Requirements
• Bridge or structure must be handicappedaccessible
• Maximum slope: 1 ft rise per 12 ft run• Maximum rise between landings: 2.5 ft• 5 ft x 5 ft landing required where ramp
changes direction• Handrails required:
– Rise greater than 0.5 ft.– Run greater than 6 ft.
Some Bridge Websites• www.pghbridges.com• www.venangoil.com/bridges.html• www.oldohiobridges.com• www.historicbridges.org• okbridges.wkinsler.com• www.iceandcoal.org/bridges/bridgefront.html• bridgehunter.com• www.bridgemeister.com• en.structurae.de/index.cfm• memory.loc.gov/ammem/collections/habs_haer/index.html
Bridge Design Software
• http://bridgecontest.usma.edu/• Free bridge designer software
Good Luck!!!
