bridges and case study

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tocomo bridge, howrah bridge, bandra warli sea link

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BRIDGES - BINDING THE GAP PRESENTED BY ---- ADITI BHATIA KAPIL GROVER KIRAN SAKSHI GUPTA

OBJECTIVE OF PRESENTATION:

OBJECTIVE OF PRESENTATION To understand different types of bridges To understand the working principles of different types of bridges To know about the details of the oldest bridge in India: Howrah Bridge To know about the Tacoma bridge and answering to where, when and why built along with other features. To know about the Bandra-Worli Sealink.

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WHAT IS A BRIDGE? A structure providing passage over an obstacle/ obstruction without closing the way underneath. The obstruction may be roads, railways, canal, aqueducts or any other structure.

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BALANCED CANTILEVER BRIDGE Construction begins at piers & span in both directions longitudinally Can be cast in-situ or segmental construction In the picture: Pierre Pflimlin Bridge Example in India: Mahatma Gandhi Setu, Patna, Bihar a nd Howrah bridge, Kolkata, West Bengal

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BALANCED CANTILEVER BRIDGE MECHANISM

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CABLE STAYED BRIDGES Deck is supported by high strength cables Cables transfer the loads to pylons Spans can be made much longer by increasing the height of pylons In the picture : Samuel Beckett Bridge Example in India: Bandra-Worli Sea Link, Mumbai, Maharashtra

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CABLE-STAYED BRIDGE MECHANISM

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SUSPENSION BRIDGES Deck is supported by high strength cables called hangers Hangers are connected to main cables which transfer the loads to pylons and end anchors Spans can be made much longer than cable stayed bridges In the picture : The golden gate bridge, california , USA Example in India: Lakshman Jhula , Rishikesh , Haridwar

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SUSPENSION BRIDGE MECHANISM

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ARCH BRIDGE Bridge with abutments at each end shaped as a curved arch. Work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. Godavari arch bridge in India (Rajahmundry) Double arch stone bridge, Japan

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ARCH BRIDGE FORCE MECHANISM

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MOVABLE BASCULE BRIDGES Used in densely populated areas where high level bridges are not feasible Many different kinds of bascule bridges are available Counterweight balances the full weight of bridge on the pier In the picture : Bascule railway bridge connecting West Seattle to Harbor Island, Seattle, Washington Example in India: Pamban bridge connecting Indian main land to Pamban islands, India

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ANIMATED VIEW OF MOVABLE BASCULE BRIDGE

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STUDY OF HOWRAH BRIDGE (INDIA)

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Calcutta and Howrah , separated by river Hoogly shared a common historical linkage towards the eventual construction of the Rabindra Setu (Howrah bridge). Constructed for the convenient plying of passenger and vehicular traffic. Sir Bradford Leslie's famous floating Pontoon bridge, the earlier avatar of the modern Howrah Bridge, initially set up in 1874. Kolkata, political capital of the nation had a synergistic effect on the commercial importance of the bridge. The location of the initial Pontoon bridge, was around 100 yards down-stream of the present Howrah Bridge (Rabindra Setu in the year 1965) after Rabindranath Tagore A FLASHBACK: THE SEAMLESS BONDS OF TIME

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OLD BRIDGE

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THE ABORTED ATTEMPT The construction of the bridge, in spite of an early and well meaning effort, had to be postponed because of outbreak of the First World War (1914 - 1919 ). The bridge was partially renewed in the years 1917 and 1927. THE FINAL DELIVERANCE : THE NEW STRUCTURAL WONDER The fourth cantilever bridge in the world. Commissioned in February 1943. Consumed 26,500 tons of steel Constructed at an approximate cost of Rs. 250 lakhs. No incidents of major casualty were reported during the construction phase of the bridge.

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BRIEF TECHNICAL PARAMETERS When commissioned in 1943,it was the 3rd longest cantilever bridge in the world Rabindra Setu: a suspension type balanced cantilever bridge Central span 1500 ft. between centers of main towers The anchor arms are 325ft. The cantilever arms are 468 ft. Long at both ends. While the middle suspended span is 564 ft. Main towers are 280 ft. high above the monoliths 76 ft. Apart at the top Bridge deck width is 71 ft. With two footpaths of 15 ft. On either side.

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All members of the super structure comprise built-up reverted sections with a combination of high tensile and mild steel. Between towers, bridge deck hangs from panel points in the lower chord of the main trusses with a series of hangers (39 pairs). Roadway beyond the towers is supported on ground leaving anchor arm free from deck loads. Bridge deck comprises 71 ft. Carriageway and 15 ft. Footway, projecting either side of the trusses and braced by longitudinal girder

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MORE ABOUT THE BRIDGE The deck system consists of cross girders hung between pairs of hungers  with pinned connection. Six rows of longitudinal stringer girders  span between cross girder. Floor joists supported transversely on top of stringers. They support a continuous pressed steel system. Over which deck concrete is laid out. JOINT SYSTEM OF BRIDGE (EXPANSION JOINTS) Longitudinal expansion and lateral sway movement of the deck are taken care of by expansion and articulation joints. There are two main expansion joints, one at each interface between the suspended span and the cantilever arms. There are expansion joints at the towers and at the interface of steel and concrete structures at both approach.

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ARTICULATION JOINTS There are total 8 articulation joints:3 at each of the cantilever arms, 2 in the suspended portions. They divide the bridge into segments with vertical pin connection between them to facilitate rotational movements of the deck. CAMBER AND TRAFFIC CLEARANCE Bridge deck has longitudinal ruling gradient of 1 in 40 from either end They are joined by a vertical curve of radius 4000 ft. Cross gradient of deck is 1 in 48 between kerbs and central 4.9mtr. is level to provide tramway housing channel in between troughing .

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FOUNDATION The main tower founded with single monoliths (55.31 x 24.8 m) in plan with 21 chambers Monoliths at Calcutta and Howrah side are founded 31.41 m and 26.53 m in below ground level respectively. Minimum headroom in carriageway is 5.8 m Freeboard for river traffic is 8.8 m

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THE TACOMA NARROWS BRIDGE What Happened, Why it Happened, How to Prevent it from Happening Again...????

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The Tacoma Narrows Bridge was located in Tacoma, Washington The third-longest suspension type bridge in the United States It was built with plate girders, steel beams used as main horizontal supports in a bridge. Total Length 5,939 feet. Center span 2,800 feet. Width 39 feet. INTRODUCTION

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The bridge opened on July 1, 1940. Its nickname, “Galloping Gertie” Due to its rolling, undulating behavior. One side of the bridge rolled higher than the other due to strong winds. The undulations were thought to be harmless, for the most part. THINGS ABOUT THE BRIDGE

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THE OLD TACOMA NARROWS BRIDGE

The Old Tacoma Narrows Bridge:

The Old Tacoma Narrows Bridge A fter Reconstruction

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THE NEW TACOMA NARROWS BRIDGE

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35 mile per hour winds excited the bridge's transverse vibration mode, with an amplitude of 1.5 feet. This motion lasted 3 hours. The wind then increased to 42 miles per hour. In addition, a support cable at mid-span snapped, resulting in an unbalanced loading condition. The bridge response thus changed to a 0.2 Hz torsional vibration mode, with an amplitude up to 28 feet . WHAT HAPPENED?

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The torsional mode shape was such that the bridge was effectively divided into two halves. The one half rotated clockwise, while the other rotated counter-clockwise. The two half spans then alternate polarities. The bridge collapsed during the excitation of this torsional mode. Specifically, a 600 foot length of the center span broke loose from the suspenders and fell a distance of 190 feet into the cold waters below.

Twisting:

Twisting This photograph shows the twisting motion of the centre span just before the structure failed..

COLLAPSE:

COLLAPSE

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The Tacoma Narrows Bridge collapsed because the designer failed to consider the aerodynamic forces at work The designer built the bridge with plate girders, steel beams used as main horizontal supports in a bridge, it caught the wind rather than letting it pass through. WHY IT REALLY HAPPENED?

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Must consider the location and geography. Used trusses, small and strong structures used to strengthen the structure which would have cancelled out the effect of the aerodynamic forces of the structure The models of the bridge were tested for wind pressures and resistance Provide sufficient stiffening supports HOW TO PREVENT IT FROM HAPPENING AGAIN?

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Aerodynamic instability, and even resonance, should always be taken into account, along with other forces of nature. Tried and “true” explanations should not be taken for granted and that ideas should always be challenged. The Tacoma Narrows Bridge introduced major changes in modern bridge engineering increasing safety and advancing engineering designs. As proof that engineers did learn from their mistakes, a new suspension bridge was built in place of the collapsed Tacoma Narrows Bridge and it remains standing today. SUMMARY

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A TRIUMPH OF PRECISION ENGINEERING

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INTRODUCTION The first cable-stayed bridge constructed in open seas in India Official name: Rajiv Gandhi Sea Link Type of bridge: Cable stayed main span, concrete-steel precast segment viaducts (bridge composed of several small spans) at either ends Total length: 5.6 kms with 8 traffic lanes Height: 126 metres Construction begin: 2000 Construction ends: 24 March 2010 Over 3000 workers were employed to work on the project.

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HOW THE FORCE IS TRANSMITTED?

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MATERIAL USED High performance concrete (M60 with micro-silica slurry) to enhance the durability. Fusion bonded epoxy coated reinforcement as anti-corrosive treatment (FBE Coating: epoxy based powder coating that is widely used to protect steel pipes ) Precast technology to ensure quality production of segments.

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STRUCTURE It consists of twin continuous concrete box girder bridge sections for traffic in each direction(a bridge in which the main beams comprise girders in the shape of a hollow box) Each bridge section, except at the cable-stayed portion, is supported on piers typically spaced 50 metres (160 ft) apart. The bridge alignment is defined with vertical and horizontal curves The bridge consists of three distinct parts: the north end viaduct, the central cable stayed spans and the south end viaduct.

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Both the viaducts used precast segmental construction. The cable-stayed bridge on the Bandra channel has a 50m-250m-250m-50m span arrangement and on the Worli channel it has a 50m-50m-150m-50m-50m span arrangement. The 20,000 tonne Bandra-end span of the bridge deck is supported by stay cables within a very close tolerance of deviations in plan and elevation. The superstructure of the viaducts were the heaviest precast segments to be built in India. Stay Cables used are ‘Parallel Wire Stay Cables’. (Each cable consists of a group of different number of steel wires. Each wire is made up of high tensile steel.)

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FOUNDATION The foundations for the BWSL's cable-stayed bridges consist of 120 reinforced concrete piles of 2,000 millimetres (6.6 ft) diameter. Those for the viaducts consist of 484 piles of 1,500 millimetres (4.9 ft). Challenge encountered: These 604 piles were driven between 6m and 34m into the substrate in geotechnical conditions that varied from highly weathered volcanic material to massive high strength rocks. Cofferdam construction have been used to construct the six metre deep foundation in the dry. (Cofferdam: a temporary enclosure built within a body of water and constructed to allow the enclosed area to be pumped out, creating a dry work environment for the major construction work to proceed)

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Osterberg cell technology used for the first time in India to check pile strength (for up to 9600 MT) i.e. a kind of load test on soil. Up to 25-m high pier in open sea, giving ample headroom to marine traffic. Use of Polytron Disc in bearings on piers for the first time in India. ( Polytron disc allows the bridge structure to have stability and flexibility of rotation, and also to oppose vibration or earth quake shock) Fig. last concrete connecting slab Fig. construction work of the bridge

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PYLON TOWER The overall tower configuration is an inverted “Y” shape with the inclined legs oriented along the axis of the bridge. The largest pylons for the bridge consist of diamond shaped 128 metres (420 ft) high concrete tower The bridge's pylon towers gradually decrease in cross-section with height. They have horizontal grooves every 3m in height

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THE TECHNICAL DATA FOR THE SUPERSTRUCTURE Max Longitudinal Gradient = 1.72% Max Crossfall camber (On a right hand bend the road would slope downwards from left to right; also called Cross Slope) = 6% Max Radius in Plan = 600m Min Radius in Plan = 246m Typical Span Length = 50m and 30m in Link Bridge Max Span Weight = 2000 tons For the fabrication of the truss, the entire structural steel (grade Fe 540) was sourced from within India.

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SOME INTERESTING FACTS ABOUT THE BRIDGE S aves time between Bandra & Worli from 45 minutes to 6 minutes. First Cable-Stay Bridge in India in open sea. The length of the bridge is 63 times the height of the Qutub Minar in Delhi.(72.5 m height of Qutab Minar) Its weight is equivalent to 50,000 African elephants. The length of the steel wires used is equivalent to the circumference of the earth. 92,000 tons of cement was utilized to make BWSL. Environment friendliness was top priority during the construction – fly ash (a waste product extracted from thermal power plants) was mixed with concrete, to make the construction durable as well as eco-friendly, thus making good use of waste material .

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Estimated Saving in fuel & Vehicle Operating cost (Voc): Rs.1500 crores per Annum Considerable Savings In Travel Time (30 to 35 Minutes time saved). Increased Speed & Reduced Delays (23 signals are avoided) Stress Free Driving Reduced Accident & Noise Pollution Reduction in Carbon Monoxide & Nitrogen Oxide levels : less vehicular pollution. Environment friendly. SUMMARY: BASIC BENEFITS OF THE BRIDGE

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REFERENCES (PRESENTATION) Essentials of bridge engineering by D. Johnson Victor www.howrahbridgekolkata.nic.in www.howrahbridgekolkata.gov.in/ details The Tacoma Narrows Bridge Disaster, November 1940: www.enm.bris.ac.uk/anm/tacoma/tacoma.html www.vibrationdata.com/Tacoma.htm Tacoma Narrows Bridge: Lessons From the Failure of a Great Machine: www.wsdot.wa.gov/TNBhistory/.../machine3.htm www.Bandraworlisealink.com www.engineeringcivil.com/bandra-worli-sea-link mycoordinates.org/making-of-bandra-worli-sea-link Bandra-Worli Sea Link (BWSL): www.brighthubengineering.com

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