BRIDGE DESIGN SAIF HAROON BY Post-Doctoral Research Associate Department of Civil & Environmental Engineering FAMU-FSU College of Engineering

FUNCTION OF A BRIDGE Bosporus Straits Bridge at Istanbul, Turkey – 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

COMPONENTS 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

COMPONENTS OF A BRIDGE Deck Girder Abutment Pier

TYPES OF BRIDGES Beam or Girder Bridge Truss Bridge Rigid Frame Bridge Arch Bridge Cable Stayed Bridge Suspension Bridge

Chesapeake Bay Bridge, Virginia GIRDER BRIDGE Typical span length 30 to 650 ft World’s longest: Ponte Costa e Silva, Brazil with a center span of 1000 ft Chesapeake Bay Bridge, Virginia

Firth of Forth Bridge, Scotland TRUSS BRIDGE Typical span length 150 to 1500 ft World’s longest: Pont de Quebec, Canada with a center span of 1800 ft Firth of Forth Bridge, Scotland

RIGID 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.

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

CABLE 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. World’s largest bridge: Tatara Bridge, Japan center span: 2900 ft. Normandie Bridge

Golden Gate Bridge, California SUSPENSION 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. Golden Gate Bridge, California

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 Types Simple Span Continuous Span Cantilever Span

LOADS 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) AASHTO – American Association of State Highway and Transportation Officials This model consists of: Design Truck Design Tandem Design Lane

DESIGN TRUCK 145 kN 35 kN 4.3 to 9.0 m 4.3 m 9.3 N/m DESIGN TRUCK

DESIGN TANDEM 110 kN 9.3 N/m 1.2 m DESIGN TANDEM

DESIGN 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 BRIDGES Concrete Steel Wood

CONCRETE 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 BRIDGES Minimum construction depth Rapid construction Steel can be formed into any shape or form Predictable life Ease of repair and demolition

WOOD 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 Concrete Abutments Three Span Wood Bridge

GIRDER CROSS-SECTIONS COMMONLY USED IN BRIDGES

COLLAPSE OF BRIDGES Poor design Inadequate stability of the foundation Fatigue cracking Wind forces Scour of footing Earthquake

Before Collapse After 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

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