Introduction to Bridges a complete guideline.pdf
- 1. A bridge is a structure that permits us to cross over an obstacle. Suppose we lay a plank across a brook. If we have a bridge. If the plank is thin in relation to its length , it will sag. In fact, if it is too long, it will collapse. This shows that we must consider the weight of a bridge itself---the “dead load”. If we stand at the middle of the plank, it sags even more. So, we must provide for the weight of whatever our bridge is designed to carry--- the “live load”. Also, when you walk across the plank, it bounces under you, illustrating the effect of a “moving live load”. Finally, there is a “wind load”. A strong wind pushes against the sides, lifts the deck, shakes the whole structure. Certainly the force of the wind is something to keep in mind. Bridges help us to connect to each other and the world. There are four main types of physical bridges. They are arch, beam, suspension and cable-stayed.
- 2. Functions : aqueduct, viaduct, highway, pedestrian etc. Materials of construction : reinforced concrete, pre- stressed concrete, steel, composite, timber etc. Form of superstructure : slab, beam, truss, arch, suspension, cable-stayed etc. Inter-span relation : simple, continuous, cantilever. Span : short, medium, long, skew, curved. Type of service and duration of use : permanent, temporary bridge, military
- 3. The two basic parts are: Substructure - includes the piers, the abutments and the foundations. Superstructure - consists of the deck structure itself, which support the direct loads due to traffic and all the other permanent and variable leads to which the structure is subjected. The connection between the substructure and the superstructure is usually made through bearings. However, rigid connections between the piers (and sometimes the abutments) may be adopted, particularly in frame bridges with tall (flexible) piers.
- 4. Bridge is a structure which provides a passage over a gap without closing the opening which is beneath that gap. The passage may be due to railway , roadway , canal & natural river etc. Initially the naturally available materials such as stone and timber were extensively used for bridges but now days artificial materials such as cement concrete & steel are utilized more in the construction of bridge.
- 5. 700 A.D. Asia 700 A.D. Asia 1,304 years 1,304 years ago ago 100 B.C. Romans 100 B.C. Romans 2,104 years ago 2,104 years ago Clapper Bridge Tree trunk Stone Arch design evenly distributes stresses Natural concrete made from mud and straw Roman Arch Bridge Great Stone Bridge in China Low bridge Shallow arch Allows boats and water to pass through
- 6. Truss Bridges Mechanics of Design Wood Suspension Bridges Use of steel in suspending cables 1900 1900 1920 1920 Prestressed Concrete Steel 2000 2000
- 7. MASONARY ARCH BRIDGE Probably first category of bridge to be involved. Aesthetically superior to slab bridges. Consist of a arch shape slab supported on two apposite wall & it was adopted earlier for small of 3 to 15m in masonry & extended up to 519m in steel & 305m in concrete has been built in the world.
- 8. Beam Bridge When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart. Beam bridges are horizontal beams supported at each end by substructure units and can be either simply supported when the beams only connect across a single span, or continuous when the beams are connected across two or more spans.
- 10. PIPE CULVERT Consist of a pipe barrel under the embankment with protection works at the entry and exit. It is suitable for cross drainage flow on relatively flat terrain & in this discharge is limited & it has negligible maintenance
- 11. Hydraulically short conduit which conveys stream flow through a roadway embankment or past some other type of flow obstruction
- 12. SLAB BRIDGE Simplest type of construction. Adopted for small bridges and culverts. Span is between 10-20m. Concrete slab cast monolithically over longitudinal girder. No. of longitudinal girders depends upon the width of road
- 13. PLATE GIRDER BRIDGE Span ranges 10 to 60m. Can be extending up to 250m in continuous construction
- 14. TRUSS BRIDGE Span 30 to 375m in simply supported case. Span 30 to 550m in cantilever combination case
- 15. SUSPENSSION BRIDGE Made up of high tensile steel cables strung in form of a centenary to which the deck is attached by steel suspenders which are made up of steel rods/members/cables. Deck can be of timber , concrete or steel spanning across the stiffening girders transmitting loads to suspenders.
- 16. 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.
- 17. A movable bridge, is a bridge that moves to allow passage usually for boats or barges.
- 19. Based upon structural action or nature of superstructure action Simply supported span bridge Continuous span bridge Cantilever bridge Arch bridge Rigid frame bridge
- 20. Based upon movement of structural parts of the bridge Fixed(permanent) bridge Movable bridge: Can opened either horizontally or vertically so as allow the river or channel traffic to pass
- 21. Based upon purpose of bridge Road bridge Railway bridge Pedestrian bridge
- 22. Base upon span length Culvert – up to span length 6m Minor bridge – up to span length 6 to 30m. Major bridge – up to span length over 30m
- 29. • The most common and basic type • Typical spans : 10m to 200m