29-05-2012, 05:45 PM
POST-TENSIONED PRESTRESSED CONCRETE GIRDER BRIDGE FOR A HIGH LEVEL ROAD WAY
POST-TENSIONED PRESTRESSED CONCRETE GIRDER BRIDGE .docx (Size: 10.38 MB / Downloads: 595)
. INTRODUCTION
A bridge project from its conception to completion involves various stages of planning, design, approval/sanction, tendering and execution. Also inspections, maintenance and repairs are continuing activities for enhancing the service life of the structure.
ACTIVITIES INVOVED:
A bridge project is required to carry out survey for the bridge location and collect requisite preliminary survey data that is required for bridge planning and design. Generally 2-3 cross sections at prospective sites are taken and the bridge length is decided for the purpose of preparing stage-I estimate needed for obtaining Approval.
Depending on site conditions, particularly the foundation conditions (which could be a guess/ interpolation at this stage) the type of bridge viz. P.S.C., R.C.C., high level, submersible etc. is decided.
For bridges having span more than 60m, detailed estimate is required to be submitted to Government for obtaining administrative approval. It is, therefore, necessary that site is to be finalized by the Engineer. So that detailed soil explorations as may be necessary could be done.
The detailed proposal is then prepared by Engineer. The detailed proposal would generally mean giving sufficient details for preparation of estimate after working out the stability of structures i.e. piers and abutments and deciding the tentative dimensions for superstructure and other components along with specifications.
DEFINITION OF A BRIDGE:
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle.
Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.
HISTORY OF A BRIDGE:
The greatest bridge builders of antiquity were the ancient Romans. The Romans built arch bridges and aqueducts that could stand in conditions that would damage or destroy earlier designs. Some stand today.
Rope bridges, a simple type of suspension bridge, were used by the Inca civilization in the Andes mountains of South America, just prior to European colonization in the 16th century.
During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich, Johannes Grubenmann, and others.
With the Industrial Revolution in the 19th century, truss systems of wrought iron were developed for larger bridges, but iron did not have the tensile strength to support large loads.
With the advent of steel, which has a high tensile strength, much larger bridges were built, many using the ideas of Gustave Eiffel.
In 1927 welding pioneer Stefan Bryła designed the first welded road bridge in the world, which was later built across the river Słudwia Maurzyce near Łowicz, Poland in 1929.
IMPORTANCE OF BRIDGE:
Bridges have always figured prominently in human history. Cities have sprung up at a bridgehead or where at first a river could be forded at any time of the year.
Examples: London, Oxford, Cambridge and Innsbruck.
Bridges add beauty to the cities.
Examples: the bridges across the river seine in Paris and the bridges across the river Thames in London.
They enhance the vitality if the cities and aid the social, cultural and economic improvements of the areas around them. Great battles have been fought for cities and their bridges. The mobility of an army at war is often affected by the availability or otherwise of the bridges to across rivers. That is why military training puts special emphasis on learning how to destroy bridges during combat and while retreating and how to build new ones quickly while advancing.
BRIDGES-TYPES
CLASSIFICATION OF BRIDGES:
Function
Material of construction
Form
Inter-span relations
Position of the bridge to the superstructure
Method of connections
Method of clearance
Length of bridge
Degree of redundancy
Type of service