Chapter 1

• Bridge engineering focuses on the design, construction, and maintenance of bridges and similar structures
• Bridges are essential transportation infrastructures that connect communities, cities, and regions
• Factors considered in bridge design include load-bearing capacity, durability, environmental impact, and aesthetic appeal
• Engineers analyze forces like traffic loads, wind, seismic activity, and temperature changes to determine materials and dimensions
• Advancements in technology have led to innovative materials like high-strength steel, prestressed concrete, and composite materials for long-span bridges
• Sustainable practices in bridge engineering aim to minimize environmental impact and ensure the longevity of structures
• Timber Bridges:

  • Constructed using timber
  • Generally for short spans or temporary bridges
  • Not suitable for heavy loads
• Masonry Bridges:

  • Constructed using bricks or stones
  • Generally for short spans and low depth canals
• Steel Bridges:

  • Constructed using steel bars, trusses, or cables
  • More durable and can bear heavy loads
• Reinforced Concrete Bridges:

  • Constructed using reinforced cement concrete
  • Stable, durable, and can bear heavy loads
• Prestressed Concrete Bridges:

  • Suited for long-span bridges
  • Blocks arranged as deck slab with girders
  • Used for bridges of increasing spans with ease of construction
• Foot bridge:

  • For humans to cross roads, rail routes, or canals by foot
  • No vehicles allowed
• Highway bridge:

  • Also known as roadway bridge
  • Used for road transportation over rivers or other routes
• Railway bridge:

  • Constructed for rail transportation
  • Truss type bridges preferred but reinforced concrete bridges also used
• Aqueduct bridge:

  • Water-carrying bridges transporting water from source to system
• Road cum railway bridge:

  • For both roadway and railway transport
  • Can have one or two floors
• Arch bridge:

  • Curve-shaped bridge with horizontal thrust restrained by abutments
  • Arch may be under the deck slab in some cases
• Girder bridge:

  • Deck slab supported by girders
  • Girders can be rolled steel, plate, or box girders
• Truss bridge:

  • Superstructure provided with trusses made of steel
  • Various types of trusses can be used
• Suspension bridge:

  • Deck slab suspended with cables and suspenders
  • Suitable for long-span bridges
• Simple bridge:

  • Simply supported beam type with two supports at ends
  • Suitable for shorter spans
• Continuous bridge:

  • More supports needed for very long spans
  • Cantilever bridge:
  • Supported at one end with another end free
  • Two cantilever portions joined for vehicles or humans
• Culvert bridge: Span length below 6 meters
• Minor bridge: Span length between 8 to 30 meters
• Major bridge: Span generally about 30 to 120 meters
• Long span bridge: Span more than 120 meters
• Deck bridge:

  • Floor positioned between high flood level and formation level
• Through bridge:

  • Superstructure completely above the formation level
• Semi-through bridge:

  • Superstructure partly above and partly below the formation level
• Alignment and location must satisfy on-bridge and under-bridge requirements
• Considerations include future variations in alignment, width of waterway, and bridge width for future roadway widening
• Route location must facilitate cost-effective design, construction, operation, and maintenance while providing desired traffic service and safety
• Bridges over waterways or floodplains must consider hydrologic and hydraulic characteristics, flood history, scour potential, and flood hazards
• Clearance Requirements:

  • Vertical clearance requirements are established to prevent collision damage to the superstructure
  • Vertical clearance is measured from the top of the roadway surface to the bottom of the lowest girder
  • Required vertical clearance for many highway bridges is 4.5 m, including 150 mm for possible future overlays
  • Horizontal clearance requirements are established to prevent collision damage to the substructure
• Environmental Considerations:

  • Impact of the bridge and its approaches on local communities, historic sites, wetlands, and other sensitive regions must be considered
  • Laws and regulations concerning encroachment on floodplains, fish, and wildlife habitats must be satisfied
  • For bridges crossing waterways, factors like stream forces, riverbed scour, removal of embankment stabilizing vegetation, and impacts to tidal dynamics must be considered
  • Design considerations for bridges with concrete components include protection of reinforcing steel and/or prestressing steel against corrosion
• Aesthetics:

  • Characteristics of aesthetically pleasing bridges include simplicity, slender girders, continuous lines, and shapes reflecting forces acting on them
  • Determinants of a bridge's appearance include vertical and horizontal geometry, superstructure type, pier and abutment placement, colors, surface textures, ornamentation, signing, lighting, and landscaping
• Superstructure:

  • Wearing Surface:
  • Resists traffic wear and can be a separate layer made of bituminous material or integral part of concrete deck
  • Thickness varies for integral wearing surface and bituminous wearing course
  • Types of wearing surfaces include Asphalt Concrete, Latex Modified Concrete, High Density-Low Slump Concrete, and Integrated Wearing Surface
  • Deck:
  • Distributes loads transversely along the bridge cross-section
• • Types of secondary members include Diaphragms, Lateral Bracing, and Portal and Sway Bracing
• • Types of bridge decks include Noncomposite and Composite Decks, Cast-in-Place Concrete Slab, Precast Prestressed Concrete Panels, Steel Orthotropic Plate, Steel Grid, Timber, Corrugated Metal, and Fiber Reinforced Polymer (FRP)
  • Primary Members:
  • Beam type primary members designed to resist flexure and shear
  • Types of primary members include stringer (or girder) such as Rolled Beam, Plate Girder, Box Girder, Steel Rigid Strut Frame, and Large Structures
  • Secondary Members:
  • Bracing between primary members to resist cross-sectional deformation and distribute vertical load
• Substructure:

  • Abutments:
  • Earth-retaining structures supporting the superstructure at the beginning and end of a bridge
  • Piers:
  • Structures supporting the superstructure at intermediate points between the end supports
  • Bearings:
  • Mechanical systems transmitting vertical and horizontal loads of the superstructure to the substructure
  • Accommodate movements between superstructure and substructure, including expansion bearings and fixed bearings
  • Pedestals:
  • Short columns under a bearing supporting a superstructure primary member
  • Backwall: