Bridge Engineering Presentation (general) 5b595q

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 WabashPittsburg 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 - at beginning or end of bridge integrated with the ground • Pier - intermediate • Span - the bridge between two s • Girder - a tall, narrow beam • Structure - the part of the bridge that carries the load

Engineering - Classification of Forces • Function of bridge: to carry a load across a distance • Due to gravity, all loads have a downward force (weight) • All bridges can be classified into the following basic types based on how they carry 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 s a weight in compression is an arch bridge • The circular arc in compression s 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 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 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 what is going on. They serve no structural purpose.

The top rods are pushed together in compression

The bottom rods

are pulled

apart in tension

Tension/Compression - Beam Photo: Todd Wilson

Tension/Compression - Truss •As a beam gets taller and taller, it becomes 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

• Pennsylvania

• Lenticular

• Warren

• Pratt

• Double Intersection Warren

• Double Intersection Pratt (Whipple) • Baltimore

• Warren Quadrangular (Lattice)

• Parker

• 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 on each end

• Continuous – Beam or truss continues over at least one between the end s

• Cantilever – One (or both) ends of a beam or truss are projected past the end of a - the projected anchor spans – A subsequent beam or truss is connected to the projected spans - the suspended span

Configuration - Simple

Photo: Todd Wilson

Configuration - Simple

Photo: Todd Wilson

Configuration - Continuous Photo: 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 s • Simple bridges are often thickest in center

Photo: Todd Wilson

Bending - Continuous • An intermediate 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 of structure 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

Suspension Photo: Todd Wilson

Cantilever Through Truss

Cantilever Deck Truss

Photo: Todd Wilson

Cantilever Through Truss & Arch

Photo: Todd Wilson

Through Arch Photo: Todd Wilson

Tied Arch Photo: 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 handicapped accessible • 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!!!

Questions? [email protected]