Bridge and Tunnel Engineering By Sandeep Jyani Sir Civil Engineering by Sandeep Jyani Bridge Engineering • Bridge is a structure which provides a passage over an obstacle like river, channel, valley or a road, without closing the way underneath. • The passage required may be for pedestrians, roads, railway or for a pipeline. Civil Engineering by Sandeep Jyani Types of Bridges • Bridges may be classified on the basis as given below: 1. Purpose: A. Road bridges B. Railway bridges C. Foot bridges D. Aqueduct (for carrying canal water) E. Viaduct (for taking roads across valleys) 2. Alignment: A. Square bridge→ if it is at right angles to obstacle B. Skew bridges → if it is not at right angles to obstacle Civil Engineering by Sandeep Jyani Types of Bridges 3. Life period: A. Permanent B. Temporary→ Temporary bridges are built during military operations, during project execution or in rescue operations. 4. Span: A. Culverts – if less than 6 m B. Minor bridge – if 8 to 30 m C. Major bridge – if 30 to 120 m D. Long span bridges – if more than 120 m. Civil Engineering by Sandeep Jyani Types of Bridges 5. Position of high flood level A. Submersible – flow of water above bridge deck level permitted during heavy rains. B. Non-submersible – all permanent bridges have deck level above the high flood level. Civil Engineering by Sandeep Jyani Types of Bridges 6. Fixed or movable: A. Fixed bridges are built but movable bridges are built across navigational 푆푤푖푛푔 퐵푟푖푑푔푒 channels so as to avoid obstacles to navigation. B. Movable bridges may be further classified as a) Swing bridges b) Lift bridges 퐿푖푓푡 퐵푟푖푑푔푒 c) Bascule bridges→In case of bascule bridges entire superstructure is rotated in vertical plane to 70° to 80° suitable hinges and counterweights are provided for easy operations. Civil Engineering by Sandeep Jyani 퐵푎푠푐푢푙푒 퐵푟푖푑푔푒 Types of Bridges 7. Location of Bridge Floor: A. Deck → when the bridge is on 푫풆풄풌 푩풓풊풅품풆 top level of the super- structure B. Semi-through → when the bridge is on intermediate level of the super- structure → C. Through type when the 푺풆풎풊 푻풉풓풐풖품풉 푩풓풊풅품풆 bridge is on bottom level of the super- structure Civil Engineering by Sandeep Jyani 푻풉풓풐풖품풉 푩풓풊풅품풆 8. Superstructure: On this basis bridges may be classified as A. Girder bridge B. Portal frame bridge C. Truss bridge D. Cantilever bridge E. Arch bridge F. Suspension bridge. Civil Engineering by Sandeep Jyani 9. Materials: A. Timber bridges B. Masonry bridges C. R.C.C. bridges D. Prestressed concrete bridges E. Steel bridges. Civil Engineering by Sandeep Jyani Bridge Elements 1. Pier: • Pier is a vertical load bearing member such as an intermediate support for adjacent ends of two bridge spans 2. Abutment: • End supports of the superstructure are known as abutments. 3. Bed block: • It is the block on the top of pier or abutment which receives load from the bearings and disperses to the pier Civil Engineering by Sandeep Jyani Bridge Elements 4. Back Fill • The material used to fill the space at the back of abutment is known as back fill. • Stone, gravel, sand, etc., are used for back filling. It should be well compacted 5. Kerb: • It is the raised portion of the edge of carriageway on both sides. • It checks the vehicle going out of the carriageway. • Width and height of kerbs are 600 mm and 225 mm. The roadside slope of kerb is 1 in 8 up to a height of 200 mm and the top portion is curved. Civil Engineering by Sandeep Jyani Bridge Elements 6. Wing walls: • They are retaining walls constructed to retain the earthwork of approach embankment behind the abutments 7. Curtain wall: • The floor provided between masonry walls below river bed is known as curtain wall. Civil Engineering by Sandeep Jyani Bridge Elements 8. Bearings: • Bearings are the devices used in long bridges to avoid development of high stresses in main girders due to temperature changes and deflections. • Shallow or fixed plate bearings are suitable for spans up to 12 m. • Deep cast base bearings are suitable for spans 12 to 20 m. • Rocker bearings are suitable for spans more than 20 m. • Sliding plate bearings are provided at one end of the girder of span 12 to 20 m. Civil Engineering by Sandeep Jyani SELECTION OF BRIDGE SITE 1. Stream should be straight. 2. Stream should be narrow with well defined and firm banks. 3. There should not be whirls and cross currents. 4. There should be high banks above high flood level on each side. 5. The site should be at reasonable proximity to the direct alignment of road. 6. The site should be geologically sound. 7. As far as possible it should not need river training works and avoid excessive under water construction works Civil Engineering by Sandeep Jyani Bridge Design • Width of bridges: • It is based on traffic survey. It may be single lane or double lane with pedestrian platform on only one side or on both side. • Length of bridge: • It depends upon the waterway. • Height of bridge: • It is 1.2 to 1.5 m above HFL. • Spans: It depends upon the type of superstructure proposed. • Masonry arch : 3 to 15 m Slab bridges : Upto 9 m • Slab bridges : Upto 9 m • Girder and beams : 10 to 60 m • Truss bridges : 30 to 375 m with simply supported ends. • Suspension bridges : Over 500 m so for maximum span built in 1990 m Cable stayed bridges : 300 to 600 m Civil Engineering by Sandeep Jyani Bridge Design • Piers: Types of piers generally used are: • Masonry piers • R.C.C. piers • The forces acting on piers are: • Vertical load or inclined reaction from the superstructure • Water pressure • Static water pressure • Dynamic pressure due to flow of water • Impact due to cross currents • Tractive force • Wind pressure • Earthquake forces Civil Engineering by Sandeep Jyani • Foundations • It may be spread foundation, pile foundation or well foundation. • The choice of foundation depends upon load expected and soil properties Civil Engineering by Sandeep Jyani Permanent Small Bridges • Causeways and culverts may be considered permanent small bridges. 1. Causeways • It is a submersible bridge, provided across a nullah or stream. • These are adopted for roads which are of minor importance. • They do not have foundation, pier or abutment. • They are concrete slabs and stone pitching at bed level or slightly higher level of stream. • Causeways may be classified as: • Flush causeway • Low level causeway • High level causeway Civil Engineering by Sandeep Jyani Permanent Small Bridges 2. Culverts • Culvert is a small bridge, the maximum Pipe culvert span not exceeding 6 m. • It may have 3 to 4 spans. • Types of culverts used are: a) Pipe culvert b) Box culvert Box culvert c) Slab culvert d) Beam and slab culvert e) Arch culvert Arch culvert Civil Engineering by Sandeep Jyani Que 1. A culvert has span less than (a) 3 m (b) 6 m (c) 9 m (d) 12 m . Civil Engineering by Sandeep Jyani Que 1. A culvert has span less than (a) 3 m (b) 6 m (c) 9 m (d) 12 m . Civil Engineering by Sandeep Jyani 2. A bridge of span 25 m may be treated as (a) culvert (b) minor bridge (c) major bridge (d) long span bridge Civil Engineering by Sandeep Jyani 2. A bridge of span 25 m may be treated as (a) culvert (b) minor bridge (c) major bridge (d) long span bridge Civil Engineering by Sandeep Jyani 3. A bridge of more than ____span is treated as long span bridge. (a) 30 m (b) 60 m (c) 90 m (d) 120 m Civil Engineering by Sandeep Jyani 3. A bridge of more than ____span is treated as long span bridge. (a) 30 m (b) 60 m (c) 90 m (d) 120 m Civil Engineering by Sandeep Jyani 4. As far as possible the alignment of a bridge should be (a) square (b) skew (c) curved (d) none of the above Civil Engineering by Sandeep Jyani 4. As far as possible the alignment of a bridge should be (a) square (b) skew (c) curved (d) none of the above Civil Engineering by Sandeep Jyani 5. Temporary bridges are built during (a) military operations (b) project executions (c) rescue operations (d) all the above Civil Engineering by Sandeep Jyani 5. Temporary bridges are built during (a) military operations (b) project executions (c) rescue operations (d) all the above Civil Engineering by Sandeep Jyani 6. Movable bridges are built across (a) streams (b) rivers (c) channels (d) dry valley Civil Engineering by Sandeep Jyani 6. Movable bridges are built across (a) streams (b) rivers (c) channels (d) dry valley Civil Engineering by Sandeep Jyani 7. A bascule bridge is a (a) fixed bridge (b) movable bridge (c) Deck bridge (d) Through Bridge Civil Engineering by Sandeep Jyani 7. A bascule bridge is a (a) fixed bridge (b) movable bridge (c) Deck bridge (d) Through Bridge Civil Engineering by Sandeep Jyani 8. Which one of the following is not a low cost bridge (a) wooden bridge (b) masonry bridge (c) floating bridge (d) movable bridge Civil Engineering by Sandeep Jyani 8. Which one of the following is not a low-cost bridge (a) wooden bridge (b) masonry bridge (c) floating bridge (d) movable bridge Civil Engineering by Sandeep Jyani 9. The end supports of a bridge superstructure are known as (a) wing walls (b) piers (c) abutments (d) bed blocks Civil Engineering by Sandeep Jyani 9. The end supports of a bridge superstructure are known as (a) wing walls (b) piers (c) abutments (d) bed blocks Civil Engineering by Sandeep Jyani 10.