Bridge Definition

Types of Bridges

Bridge Components

Aesthetic in Bridge Design

Selection criterion of a Bridge Type

Quiz

What is a Bridge?

Bridge is a structure which covers a gap

Generally bridges carry a road or railway across a natural orartificial obstacle such as, a river, canal or another railwayor another road

Bridge is a structure corresponding to the heaviestresponsibility in carrying a free flow of transport and is themost significant component of a transportation system incase of communication over gaps for whatever reason suchas aquatic obstacles, valleys and gorges etc.

700 A.D. Asia700 A.D. Asia

1,304 years 1,304 years agoago

100 B.C. Romans100 B.C. Romans2,104 years ago2,104 years ago

Clapper Bridge

Tree trunkStone

Arch design evenly distributesstressesNatural concretemade from mudand straw

Roman Arch Bridge

History of Bridge DevelopmentHistory of Bridge Development

Great Stone Bridge in China

Low bridgeShallow archAllows boatsand water to passthrough

History of Bridge DevelopmentHistory of Bridge Development

Truss BridgesMechanics of DesignWood

Suspension Bridges

Use of steel in suspending cables

1900 1900

1920 1920

Prestressed ConcreteSteel

2121STSTCENTURYCENTURY

Compression Tension

Basic Concepts Basic Concepts

Span - the distance between two bridge supports, whether they are columns, towers or the abutments.

Compression

Tension -

Force -

Concrete has good compressive strength, but extremely weak tensile strength. steel and cables are good in tesion

Basic Concepts Basic 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

Beam

Pier

Load - weight on a structure

There are six main types of bridges:1. beam bridges2. cantilever bridges 3. arch bridges4. suspension bridges 5. cable-stayed bridges and 6. truss bridges

Types of Bridges

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 45m.

beam bridges

ForcesWhen something pushes down on the beam,

the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

Beam bridge

A cantilever bridge is a bridge built using cantilevers: structures that project horizontally into space, supported on only one end.

cantilever 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.

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.

Types of BridgesTypes of Bridges

Arch BridgesArch Bridges

Suspension BridgesSuspension Bridges

This kind of bridges can span 600m to 2500m -- way fartherthan any other type of bridge! Most suspension bridges have atruss system beneath the roadway to resist bending andtwisting.

Types of BridgesTypes of 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.

Types of BridgesTypes of Bridges

Suspension BridgesSuspension Bridges

cable-stayed bridges

The cable stayed bridge is newer than the other types of bridge. Large upright steel supports are used to transmit the load into the ground.

Truss 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.

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.

Types of Types of BridgesBridges

Floating BridgeFloating Bridge

Bridge is the KEY ELEMENTin a Transportation System

What is a Bridge?

Structures for Transportation

Beauty can be expressed in the

structural efficiency, simplicity, and

repetition of a bridge.

Mayur Viaduct, France

SubstructureFoundation (Pile/Spread footing)Pier (Column)Abutment

SuperstructureAny structure above bearingWearing surface

Bridge Components

Bridge Components

Bridge Planning

Traffic StudiesHydro technical StudiesGeotechnical StudiesEnvironmental ConsiderationsAlternatives for Bridge TypeEconomic Feasibility Bridge Selection and Detailed Design

Span>6m BridgeSpan100m

Bridge Span Length

Steel Concrete Timber Hybrid Stone/Brick FRP

Pedestrian Highway Railroad

Short Medium Long

Slab Girder Truss Arch Suspension Cable-Stayed

MaterialMaterial

UsageUsage

Span

Structural form

Types of Bridges

Material and FabricationMaterialsMasonry (brick, rock)

Timber

Reinforced Concrete

Prestressed Concrete

Iron

Steel

Composites

FabricationPrecast (RC, PC)

Cast in place (RC, PC)

Pre tensioned (PC)

Post tensioned (PC)

Prefabricated (Steel)

Rivet (steel)

Bolted (steel, timber)

Types of Bridges

Basic types based on structural form:

ArchBeamCantileverTrussCable StayedSuspension

Types of Bridges

Types of Bridges

Arch BridgeArch bridges are one of the oldest types of

bridges and have great natural strength. Instead of pushing straight down, the weight

of an arch bridge is carried outward along the curve of the arch to the supports at each end.

These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out.

Forces

When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

Beam/Girder BridgeThe most basic type of bridge

Typically consists of a beam simplysupported on each side by a support andcan be made continuous later

Typically inexpensive to build

Types of Bridges

Beam/Girder BridgeCurrently, most of the beam bridgesare precast (in case of RC and PC) orprefabricated

Most are simply-supported

Some are made continuous on site

Simply supported

Cantilever

Continuous

Types of Bridges

Cantilever BridgeIn a cantilever bridge, the roadway isconstructed out from the pier in twodirections at the same time so that theweight on both sides counterbalanceeach other

Notice the larger section at thesupport to resist the negative moments

Firth of Forth Bridge, Scotland521m span

Types of Bridges

Truss BridgeAll beams in a truss bridge are straight.Trusses are comprised of many small beamsthat together can support a large amount ofweight and span great distances.

Typical Span lengths: 40m-500m

Types of Bridges

Suspension bridge needs to have very strong main cables

Cables are anchored at the abutment

Suspension Bridges

London Tower Bridge (1894),UK

Types of Bridges

Types of Bridges

Cable-stayed Bridge

All the forces are transferred fromthe deck through the cables to thepylon

Roadway deck can be : (prestressed) Concrete Box Deck Steel Box Deck Steel Truss Deck