BRIDGE DESIGN BY SAIF HAROON Post Doctoral Research Associate Department of Civil Environmental Engineering FAMU FSU College of Engineering FUNCTION OF A BRIDGE To connect two communities which are separated by streams valley railroads etc Bosporus Straits Bridge at Istanbul Turkey 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 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 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 Scotlan 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 Larimer Avenue Bridge Pittsburgh Typical span length 130 ft 500 ft World s longest New River Gorge Bridge U S A with a center span of 1700 ft 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 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 145 kN 35 kN 4 3 to 9 0 m 4 3 m 9 3 N m DESIGN TRUCK DESIGN TANDEM 110 kN 110 kN 1 2 m 9 3 N m DESIGN TANDEM DESIGN PRINCIPLES Resistance effect of the applied loads Allowable Stress Design ASD Strength of the Member Factor of Safety x Applied Load Load and Resistance Factor Design LRFD iQi i Rn Where Qi Effect of loads Rn Nominal resistance i Statistically based resistance factor applied to the force effects i Statistically based resistance factor applie to 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 geometri 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 Length 12 828 feet Suspension Materials Steel Cost 4 3 billion Type Span 6 527 feet SUNSHINE SKYWAY BRIDGE USA Completion Date 1987 Cost 244 Million Length 29 040 feet Stayed Type Cable Materials Steel Concrete Span 1200 NEW RIVER GORGE BRIDGE USA Completion Date 1978 Length 4 224 feet Materials Steel Cost 37 Million Type Arch Span 1700 feet THANK YOU