Title: Lean Construction
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2By Dr. Attaullah ShahSwedish College of
Engineering and Technology Wah Cantt.
- CE-407
- Lec-04
- Structural Engineering
- Bridges-II
- ( ACI
3Elevation and cross section of Bridges
4Arch and suspension Bridges
5Some important definitions
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19Bridges
20History of Bridge Development
100 B.C. Romans 2,104 years ago
700 A.D. Asia 1,304 years ago
Clapper Bridge
- Arch design
- evenly distributes
- stresses
- Natural concrete
- made from mud
- and straw
Great Stone Bridge in China
- Low bridge
- Shallow arch
- Allows boats
- and water to pass
- through
21History of Bridge Development
1900
1920
Truss Bridges
2000
Suspension Bridges
- Use of steel in suspending cables
- Prestressed Concrete
- Steel
22Basic Concepts
Span - the distance between two bridge supports,
whether they are columns, towers or the wall of a
canyon.
Force -
Compression Tension -
Concrete has good compressive strength, but
extremely weak tensile strength. What about
steel cables?
23Basic Concepts
Beam - a rigid, usually horizontal, structural
element
Pier - a vertical supporting structure, such as a
pillar
Cantilever - a projecting structure supported
only at one end, like a shelf bracket or a diving
board
Load - weight on a structure
24Types of Bridges
- Basic Types
- Truss Bridge
- Beam Bridge
- Arch Bridge
- Suspension Bridge
- Floating Bridge
Floating
Truss
Beam
Arch
Suspension
The type of bridge used depends on the obstacle.
The main feature that controls the bridge type is
the size of the obstacle.
25Truss Bridge
All beams in a truss bridge are straight. Trusses
are comprised of many small beams that together
can support a large amount of weight and span
great distances.
26Types of Bridges
Beam Bridge
Consists of a horizontal beam supported at each
end by piers. The weight of the beam pushes
straight down on the piers. The farther apart its
piers, the weaker the beam becomes. This is why
beam bridges rarely span more than 250 feet.
27Types of Bridges
Beam Bridge
Forces When something pushes down on the beam,
the beam bends. Its top edge is pushed together,
and its bottom edge is pulled apart.
28Types of Bridges
Arch Bridges
The arch has great natural strength. Thousands of
years ago, Romans built arches out of stone.
Today, most arch bridges are made of steel or
concrete, and they can span up to 800 feet.
29Types of Bridges
Arch Bridges
Forces The arch is squeezed together, and this
squeezing force is carried outward along the
curve to the supports at each end. The supports,
called abutments, push back on the arch and
prevent the ends of the arch from spreading apart.
30Types of Bridges
Suspension Bridges
This kind of bridges can span 2,000 to 7,000 feet
-- way farther than any other type of bridge!
Most suspension bridges have a truss system
beneath the roadway to resist bending and
twisting.
31Types of Bridges
Suspension Bridges
Forces In all suspension bridges, the roadway
hangs from massive steel cables, which are draped
over two towers and secured into solid concrete
blocks, called anchorages, on both ends of the
bridge. The cars push down on the roadway, but
because the roadway is suspended, the cables
transfer the load into compression in the two
towers. The two towers support most of the
bridge's weight.
32Types of Bridges
Floating Bridge
- Pontoon bridges are supported by floating
pontoons with sufficient buoyancy to support the
bridge and dynamic loads. - While pontoon bridges are usually temporary
structures, some are used for long periods of
time. - Permanent floating bridges are useful for
traversing features lacking strong bedrock for
traditional piers. - Such bridges can require a section that is
elevated, or can be raised or removed, to allow
ships to pass.
33Floating Bridges
Retractable!
But high maintenance!
34Bridge Engineering
- How do the following affect your structure?
- Ground below bridge
- Loads
- Materials
- Shapes
35Some Uses of Bridges
- Walkways
- Highways/Roads
- Railways
- Pipelines
- Connecting lands
- Crossing rivers and canyons
36Types of Bridges
- Arch
- Truss
- Cantilever
- Cable-Stayed
- Suspension
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43What makes a bridge stay up?
- Forces
- Compression a pushing or squeezing force
- Tension a pulling or stretching force
44Arch Bridges
- Keystone the wedge-shaped stone of an arch that
locks its parts together - Abutments the structures that support the ends
of the bridge
45Arch Bridges
46Arch Bridges
- Where have you seen these bridges?
47Cold Spring Arch Bridge, Santa Barbara, CA
48Marsh Rainbow Arch, Riverton, KS
49Pont du Gard, Nimes, France
50Cable-Stayed Bridges
- Piers the vertical supporting structures
- Cables thick steel ropes from which the decking
is suspended - Decking the supported roadway on a bridge
51Cable-Stayed Bridges
- Works by Tension AND Compression
52Cable-Stayed Bridges
- Where have you seen these bridges?
53Zakim Bridge, Boston, MA
54Sunshine Skyway Bridge, Tampa, FL
55Sundial Bridge, Redding, CA
56Suspension Bridges
- Similar to Cable-Stayed
- Different construction method
57Suspension Bridges
- Works by Tension and Compression
58Suspension Bridges
- Where have you seen these bridges?
59Golden Gate Bridge, San Francisco, CA
60Brooklyn Bridge, Brooklyn, NY
61Verrazano-Narrows Bridge, New York, NY
62Other Types
Truss Southern Pacific Railroad Bridge, Tempe, AZ
Cantilever Firth of Forth-Forth Rail Bridge,
Edinburgh, Scotland
63FUNCTION OF A BRIDGE
To connect two communities which are separated by
streams, valley, railroads, etc.
- Replaces a slow ferry
- boat trip
- Connects two continent
- Built in 1973
- Total length is 5000 ft
64COMPONENTS OF A BRIDGE
- Deck or Slab supported roadway on abridge
- Beam or Girder A rigid, usually horizontal,
- structural
element - Abutment The outermost end supports on a
- bridge, which carry the
load from - the deck
- Pier A vertical supporting structure, such as a
- pillar
- Foundation
65COMPONENTS OF A BRIDGE
66TYPES OF BRIDGES
- Beam or Girder Bridge
- Truss Bridge
- Rigid Frame Bridge
- Arch Bridge
- Cable Stayed Bridge
- Suspension Bridge
67GIRDER BRIDGE
- Typical span length 30 to
- 650 ft
- Worlds longest Ponte Costa
- e Silva, Brazil with a center
- span of 1000 ft
68TRUSS BRIDGE
- Typical span length
- 150 to 1500 ft
- Worlds longest
- Pont de Quebec, Canada
- with a center span of
- 1800 ft
Firth of Forth Bridge, Scotland
69RIGID FRAME BRIDGE
- Girders and piers act together
- Cross-sections are usually I-shaped or
box-shaped. - Design calculations for rigid
- frame bridges are more
- difficult than those of simple
- girder bridges.
70ARCH BRIDGE
- After girders, arches are the second oldest
bridge type. - Arches are good choices for crossing valleys and
rivers - Arches can be one of
- the more beautiful
- bridge types.
- Typical span length
- 130 ft 500 ft.
- Worlds longest
- New River Gorge Bridge, U.S.A. with a center
span of - 1700 ft.
71CABLE STAYED BRIDGE
- Continuous girder with
- one or more towers
- erected above in the
- middle of the span.
- From these towers
- cables stretch down
- diagonally and support
- the girder.
- Typical span length
- 350 to 1600 ft.
- Worlds largest bridge
- Tatara Bridge, Japan
- center span 2900 ft.
72SUSPENSION BRIDGE
- Continuous girder with one or more towers
erected above in the middle of the span. - At both ends of the bridge, large anchors or
counter weights are placed to hold the ends of
the cables. - Typical span length
- 250 to 3000 ft.
73Factors Describe a Bridge
- Four main factors are used in describing a
bridge - Span (simple, continuous, cantilever)
- Material (stone, concrete, metal, etc.)
- Placement of the travel surface in relation to
the - structure (deck, through)
- Form (beam, arch, truss, etc.).
74Basic Span Types
75LOADS ON BRIDGES
- Permanent Loads remain on the bridge for an
- extended period of time (self weight of the
bridge) - Transient Loads loads which are not permanent
-
- - gravity loads due to vehicular, railway and
- pedestrian traffic
- - lateral loads due to water and wind, ice
floes, - ship collision, earthquake, etc.
76VEHICULAR DESIGN LOADS (HL 93)
- AASHTO American Association of State Highway
- and Transportation
Officials - This model consists of
- Design Truck
- Design Tandem
- Design Lane
77DESIGN TRUCK
78DESIGN TANDEM
79DESIGN PRINCIPLES
Resistance effect of the applied loads
Load and Resistance Factor Design (LRFD) ? ??iQi
fi Rn Where, Qi Effect of loads
Rn Nominal resistance ?i
Statistically based resistance factor
applied to the force effects fi
Statistically based resistance factor applied to
the nominal resistance
? Load modification factor
80MATERIALS FOR BRIDGES
81CONCRETE BRIDGES
- Raw materials of concrete cement, fine
- aggregate coarse aggregate, water
- Easily available
- can be designed to satisfy almost any geometric
- alignment, straight to curved
- can be cast-in-place or precast
- Compressive strength of concrete range from
- 5000 psi to 8500 psi
- Reinforced concrete and prestressed concrete
82STEEL BRIDGES
- Minimum construction depth
- Rapid construction
- Steel can be formed into any shape or form
-
- Predictable life
- Ease of repair and demolition
83WOOD BRIDGES
- Convenient shipping to the job site
- Relatively light, lowering transportation and
initial - construction cost
- Light, can be handled with smaller construction
- equipment
- Approx. 12 of the bridges in US are wood
bridges - Commonly used for 20-80 ft span
84Wood Bridge on Concrete Abutments
Three Span Wood Bridge
85GIRDER CROSS-SECTIONS COMMONLY USED IN BRIDGES
86COLLAPSE OF BRIDGES
- Poor design
- Inadequate stability of the foundation
- Fatigue cracking
- Wind forces
- Scour of footing
- Earthquake
87Before Collapse
After Collapse
88AKASHI KAIKYO BRIDGE, JAPAN
Completion Date 1998 Cost 4.3
billion Length 12,828 feet Type
Suspension Materials Steel Span 6,527 feet
89SUNSHINE SKYWAY BRIDGE, USA
Completion Date 1987 Cost 244
Million Length 29,040 feet Type Cable
Stayed Materials Steel, Concrete Span 1200
feet
90NEW RIVER GORGE BRIDGE, USA
Completion Date 1978 Cost 37 Million Length
4,224 feet Type Arch Materials Steel Span
1700 feet