Disasters And Failures

Front 1

the bridges own weight

Back 1

dead load

Front 2

the weight of a bridges traffic

Back 2

live load

Front 3

forces exerted on the bridge by water, wind, etc.

Back 3

environmental load

Front 4

Equation for force

Back 4

Force=mg

Front 5

measurement of the amount of material an object contains

Back 5

mass

Front 6

measurement of the change in velocity of an object

Back 6

acceleration

Front 7

objects in motion tend to stay in motion; objects in rest tend to stay in rest unless an outside force acts upon them

Back 7

First Law

Front 8

The rate of change of the momentum of a body is directly proportional to the net force acting on it; the direction f the change in momentum takes place in the direction of the net force

Back 8

Second Law

Front 9

To every action there is an equal but opposite reaction

Back 9

Third Law

Front 10

force that tries to push material together

Back 10

compression

Front 11

best and worst materials to handle compression

Back 11

iron
concrete

Front 12

static force that tries to stretch a material

Back 12

tension

Front 13

best and worst materials at handling tension

Back 13

steel
concrete

Front 14

force that tries to deform part of a material

Back 14

shear

Front 15

To handle shear, a material should:

Back 15

1) withstand the required load deformation without breaking
2) have little or no permanent deformation after the force is removed

Front 16

best and worst materials to handle shear

Back 16

steel
wood

Front 17

force that tries to twist a material

Back 17

Torsion

Front 18

best and worst materials for handling torsion

Back 18

steel
concrete

Front 19

Earliest bridge form

Back 19

simple beam

Front 20

Used when you need a short simle bridge

Back 20

simple beam

Front 21

usedwhen you can easily secure the piers to the stream bed or canyon

Back 21

simple beam

Front 22

Materials that beams can be made from

Back 22

wod
reinforced concrete
steel

Front 23

As the live load moves over the beam, directly under to load:

Back 23

1) the top f the beam is compressed
2) the bottom of the beam is stretched
3) if the beam cant handle these stresses, then it will fall

Front 24

Using a simple beam, the bridge's beams must be either:

Back 24

1) short, which increases the number of pier needed
2) very strong, which increases costs and limits the materials that can be used

Front 25

simplest modicfication to the simple beam bridge

Back 25

truss bridge

Front 26

Truss beam bridge used when:

Back 26

1) you need a strong bridge to cross easy terrain
2) you can easily secure strong piers t the overpass, stream bed or canyon floor

Front 27

This bridge distributes compression and tension forces under the live load

Back 27

truss beam

Front 28

Physiscs of Truss Beam Bridge

Back 28

1) tension travels along the beam and into the supports
2) compression travels along the truss and into the supports
3) these forces are reversed when using a deck truss

Front 29

Members in a truss beam usually only experience:

Back 29

Tensin OR Compression, not both

Front 30

Advantages of cantilever bridges

Back 30

1) Span a greater distance with fewer supports
2) Bare a large live load

Front 31

Materials a truss beam can be made from

Back 31

wood
steel

Front 32

This bridge is like a suspension bridge but uses truss members instead of cables

Back 32

Cantilever

Front 33

first type of bridge to be built on large scale

Back 33

Arch

Front 34

materials used to build an arch bridge

Back 34

any material that can handle high compression

Front 35

greatly reduces the ability of the beam above it to flex; littel or no tension is generated

Back 35

Arch

Front 36

Cable based bridge designs increase the effects of:

Back 36

1) Shear and Torsion forces
2) Harmonic Resonance

Front 37

Physics of a Cable Stayed

Back 37

1) Bridges beam is suspended from cables that are under tension from the bridges dead load
2) Cables are connected to a tower which is under compression from the bridges dead load
3) Any additional compression or tension from the live or environmental load is tranferred by these cables to the tower where it increases or decreases the towers compression

Front 38

Physics of the Suspension Bridge

Back 38

Suspension bridge works much like a cable stayed but cables from beam are connected to another cable

Front 39

Three Ages of Bridges

Back 39

The Age of Stone
The Age of Iron
The Age of Steel and Individuals

Front 40

The Five Bridge Failures

Back 40

Tay
Quebec
Falls View
Tacoma Narrows
Silver

Front 41

Tay Bridge Design

Back 41

Truss beam bridge with iron beams sitting on iron and masonry piers; center section was elevated

Front 42

Tay Bridge Events of the Disaster

Back 42

Storm with 78 mph winds hits the bridge; bridge's center span collapses under the weight of a passenger train carrying 75 people

Front 43

Tay Bridge Design and Construction Problems

Back 43

1) Bridge not designed to withstand the types of gales normally found on the Scotish Coast
2) Center piling could not be driven to bedrock, so an iron truss was used intead of the normal masonry pier
3) The iron used on the bridge wasnt tested properly

Front 44

Tay Bridge Maintenance and Operations Problems

Back 44

1) Designer did nothing to ensure the bridge was being inspected
2) No one from the NBR inspected the bridge
3) Trains ignored the 25 mph bridge speed limit

Front 45

Lessons learned at the Tay

Back 45

1) Bridge design and construction need to be taken seriously
2) Iron should be replaced by steel in future large bridge projects
3) When crossing a large body of water, bridge designs that reduced the number of piers should be used

Front 46

Bridges the St. Lawrence

Back 46

Quebec Bridge

Front 47

Longest cantilever bridge ever built

Back 47

Quebec Bridge

Front 48

Quebec Events of the Disaster (1)

Back 48

1) Consulting Engineer Claims Ill Health and leaves cunstruction to recent graduate
2) Underfunded; Corners are cut in testing
3) Work continues without permission of the engineer
4) South arm of the bridge collapses during contruction

Front 49

Quebec Events of the Disaster (2)

Back 49

1) New design team used stronger nickel-steel
2) Short cantilever arms joined by a center suspended span
3) boat towed a center section to the middle of the river to join it with the cantilever arms
4) steel casting on the center section failed as it was being installed and it falls into river

Front 50

Lessons Learned at Quebec

Back 50

1) Designs must be fully tested
2) Construction team must function like a real team
3) Even with the best design, things go wrong
4) Trying to save money on the front end costs you on the back end

Front 51

Steel arch bridge located just north of Niagra Falls

Back 51

Falls View Bridge

Front 52

Events of the Falls View Bridge

Back 52

1) Arch extended too far out into the gorge
2) Ice built up around its base
3) Bridge was protected by blasting the ice away; protective walls were added later
4) Bridge fell into gorge as battle with the ice was lost

Front 53

Events of the Tacoma Narrows Bridge

Back 53

1) Problems came with the road way
2) Too light; solid plate girders made it sway in the wind
3) Bridge tore itself apart during 42 mph wind

Front 54

Lessons Learned at the Tacoma Narrows

Back 54

Commission that studied the disaster didnt want to blame the designer and concluded that the cause couldnt be determined

Front 55

Suspension bridge that Spanned the Ohio River between Point Pleasant, WV and Kanauga, OH

Back 55

Silver Bridge

Front 56

Design of the Silver Bridge

Back 56

1) Suspension bridge
2) Center span was supported by anchorages on either side
3) used eyebar linked chains instead of cables to support a fairly large truss
4) Constructed primarily out of carbon steel

Front 57

Events of Silver Bridge

Back 57

1) Live load on the bridge was larger than normal due to christmas traffic
2) Eyebar of the north side chain failed near a pin causing it to snap
3) Unable to support both the dead and live loads of the center span itself, the south chain snapped
4) Center span then collapsed

Front 58

Lessons Learned at the Silver Bridge

Back 58

1) National Bridge Inspection Standards were enacted by law forcing all US bridges to be routinely inspected ad repaired
2) This was followed by a number of funding laws which gave the state money to fix most of the problems found in these inspections

Front 59

Summary of Lessons Learned

Back 59

1) Bridges dont build themselves
2) Bridges dont take care of themselves
3) Building a "cheap" bridge is most often not cheap
4) Learge engineering projects are really bad playgrounds for egos and half hearted commitments to work