BRIDGE DESIGNBRIDGE DESIGN

BYBY

SAIF HAROONSAIF HAROONPost-Doctoral Research AssociatePost-Doctoral Research Associate

Department of Civil & Environmental EngineeringDepartment of Civil & Environmental EngineeringFAMU-FSU College of EngineeringFAMU-FSU College of Engineering

FUNCTION OF A BRIDGEFUNCTION OF A BRIDGE

To connect two To connect two communities which are communities which are separated by streams, separated by streams, valley, railroads, etc.valley, railroads, etc.

• Replaces a slow ferry Replaces a slow ferry boat tripboat trip• Connects two continentConnects two continent• Built in 1973Built in 1973• Total length is 5000 ftTotal length is 5000 ft

Bosporus Straits Bridge Bosporus Straits Bridge at Istanbul, Turkey –at Istanbul, Turkey –

COMPONENTS OF A BRIDGECOMPONENTS OF A BRIDGE

• Deck or Slab:Deck or Slab: supported roadway on abridge supported roadway on abridge

• Beam or Girder:Beam or Girder: A rigid, usually horizontal, A rigid, usually horizontal, structural elementstructural element

• Abutment:Abutment: The outermost end supports on a The outermost end supports on a bridge, which carry the load from bridge, which carry the load from the deckthe deck

• Pier:Pier: A vertical supporting structure, such as a A vertical supporting structure, such as a pillarpillar

• FoundationFoundation

DeckDeck

GirderGirder

AbutmentAbutment

PierPier

COMPONENTS OF A BRIDGECOMPONENTS OF A BRIDGE

TYPES OF BRIDGESTYPES OF BRIDGES

•Beam or Girder BridgeBeam or Girder Bridge•Truss BridgeTruss Bridge•Rigid Frame BridgeRigid Frame Bridge•Arch BridgeArch Bridge•Cable Stayed BridgeCable Stayed Bridge•Suspension BridgeSuspension Bridge

GIRDER BRIDGEGIRDER BRIDGE

Chesapeake Chesapeake Bay Bridge, Bay Bridge,

VirginiaVirginia

• Typical span length 30 to 650 ft

• World’s longest: Ponte Costa e Silva, Brazil with a center span of 1000 ft

TRUSS BRIDGETRUSS BRIDGE

Firth of Forth Bridge, ScotlandFirth of Forth Bridge, Scotland

• Typical span length 150 to 1500 ft

• World’s longest: Pont de Quebec, Canada with a center span of 1800 ft

RIGID FRAME BRIDGERIGID FRAME BRIDGE

•Girders and piers act togetherGirders and piers act together

•Cross-sections are usually I-shaped or box-shaped.Cross-sections are usually I-shaped or box-shaped.

•Design calculations for rigid Design calculations for rigid frame bridges are more frame bridges are more difficult than those of simple difficult than those of simple girder bridges.girder bridges.

ARCH BRIDGEARCH BRIDGE

• After girders, arches are the second oldest bridge type.After girders, arches are the second oldest bridge type.

• Arches are good choices for crossing valleys and rivers Arches are good choices for crossing valleys and rivers

• Arches can be one of Arches can be one of the more beautiful the more beautiful bridge types.bridge types.

• Typical span lengthTypical span length 130 ft – 500 ft.130 ft – 500 ft.

• World’s longest:World’s longest: New River Gorge Bridge, U.S.A. with a center span of New River Gorge Bridge, U.S.A. with a center span of 1700 ft.1700 ft.

Larimer Avenue Bridge, Pittsburgh Larimer Avenue Bridge, Pittsburgh

CABLE STAYED BRIDGECABLE STAYED BRIDGE

Normandie Normandie BridgeBridge

• Continuous girder with Continuous girder with one or more towers one or more towers erected above in the erected above in the middle of the span.middle of the span.• From these towers From these towers cables stretch down cables stretch down diagonally and support diagonally and support the girder.the girder.• Typical span lengthTypical span length 350 to 1600 ft.350 to 1600 ft.• World’s largest bridge:World’s largest bridge: Tatara Bridge, JapanTatara Bridge, Japan center span: 2900 ft.center span: 2900 ft.

SUSPENSION BRIDGESUSPENSION BRIDGE

• Continuous girder Continuous girder with one or more with one or more towers erected above towers erected above in the middle of the in the middle of the span.span.

• At both ends of the At both ends of the bridge, large anchors bridge, large anchors or counter weights are or counter weights are placed to hold the placed to hold the ends of the cables.ends of the cables.

• Typical span lengthTypical span length 250 to 3000 ft.250 to 3000 ft.

Golden Gate Bridge, Golden Gate Bridge, CaliforniaCalifornia

Factors Describe a Bridge Factors 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.).

Basic Span TypesBasic Span Types

Simple Span

Continuous Span

Cantilever Span

LOADS ON BRIDGESLOADS 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.

VEHICULAR DESIGN LOADS (HL 93)VEHICULAR DESIGN LOADS (HL 93)

• AASHTO – American Association of State Highway and Transportation Officials

This model consists of:

• Design Truck• Design Tandem• Design Lane

145 kN 145 kN 35 kN

4.3 to 9.0 m 4.3 m

9.3 N/m

DESIGN TRUCK

DESIGN TRUCKDESIGN TRUCK

110 kN 110 kN

9.3 N/m

1.2 m

DESIGN TANDEM

DESIGN TANDEMDESIGN TANDEM

DESIGN PRINCIPLESDESIGN PRINCIPLES

Resistance ≥ effect of the applied loads

Strength of the Member ≥ Factor of Safety x Applied Load

Allowable Stress Design (ASD):

Load and Resistance Factor Design (LRFD):η ∑γiQi ≤ φi Rn

Where, Qi = Effect of loads Rn = Nominal resistance γi = Statistically based resistance factor applied to the force effects

φi = Statistically based resistance factor applied to the nominal resistance η = Load modification factor

MATERIALS FOR BRIDGESMATERIALS FOR BRIDGES

• Concrete

• Steel

• Wood

CONCRETE BRIDGESCONCRETE 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

STEEL BRIDGESSTEEL BRIDGES

• Minimum construction depth

• Rapid construction

• Steel can be formed into any shape or form • Predictable life

• Ease of repair and demolition

WOOD BRIDGESWOOD 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

Wood Bridge on Wood Bridge on Concrete AbutmentsConcrete Abutments

Three Span Wood Three Span Wood Bridge Bridge

GIRDER CROSS-SECTIONS GIRDER CROSS-SECTIONS COMMONLY USED IN BRIDGESCOMMONLY USED IN BRIDGES

COLLAPSE OF BRIDGESCOLLAPSE OF BRIDGES

• Poor design

• Inadequate stability of the foundation

• Fatigue cracking

• Wind forces

• Scour of footing

•Earthquake

BeforeBeforeCollapseCollapse

After CollapseAfter Collapse

AKASHI KAIKYO BRIDGE, JAPAN

Completion Date: 1998 Cost: $4.3 billion

Length: 12,828 feet Type: Suspension

Materials: Steel Span: 6,527 feet

SUNSHINE SKYWAY BRIDGE, USA

Completion Date: 1987 Cost: $244 Million

Length: 29,040 feet Type: Cable Stayed

Materials: Steel, Concrete Span: 1200 feet

NEW RIVER GORGE BRIDGE, USA

Completion Date: 1978 Cost: $37 Million

Length: 4,224 feet Type: Arch

Materials: Steel Span: 1700 feet

THANK YOUTHANK YOU