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Cable stayed bridge

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Cable stayed bridge

  1. 1. ANALYSIS & DESIGN OF CABLE STAYED BRIDGE Supervisor : Dr /Maher Moustafa El-abd1
  2. 2. INTRODUCTION  Cables stretch diagonally between these pillars or towers and the beam .These cables support the beam  A cable-stayed bridge, one of the most modern bridges, consists of a continuous strong beam (girder) with one or more pillars or towers in the middle  The cables are anchored in the tower rather than at the end 2
  3. 3. ADVANTAGES OF CABLE STAYED BRIDGES  much greater stiffness than the suspension bridge, so that deformations of the deck under live loads are reduced  can be constructed by cantilevering out from the tower - the cables act both as temporary and permanent supports to the bridge deck  for a symmetrical bridge (i.e. spans on either side of the tower are the same), the horizontal forces balance and large ground anchorages are not required. 3
  4. 4. DIFFERENCE BETWEEN CABLE STAYED BRIDGE AND CABLE SUSPENSION BRIDGE  A multiple-tower cable-stayed bridge may appear similar to a suspension bridge, but in fact is very different in principle and in the method of construction.  In the suspension bridge, a large cable hangs between two towers, and is fastened at each end to anchorages in the ground or to a massive structure.  These cables form the primary load-bearing structure for the bridge deck. Before the deck is installed, the cables are under tension from only their own weight.  Smaller cables or rods are then suspended from the main cable, and used to support the load of the bridge deck, which is lifted in sections and attached to the suspender cables.  The tension on the cables must be transferred to the earth by the anchorages, which are sometimes difficult to construct owing to poor soil conditions. 4
  5. 5. COMPONENTS OF CABLE STAYED BRIDGE 5
  6. 6. LOAD TRANSMISSION soil piles Pile cap pylons Cables Deck Tension Compression 6
  7. 7. CLASSIFICATIONS  Based on arrangements of the cables • Radiating • Harp • Fan • star  Based on the shape of pylon • A-type • H-type • Y-type 7
  8. 8. radial : cables connect evenly throughout the deck, but all converge on the top of the pier harp : cables are parallel, and evenly spaced along the deck and the pier fan : a combination of radial and harp types star-shaped : cables are connected to two opposite points on the pier 8
  9. 9. SHAPES OF PYLON 9
  10. 10. TYPES OF DECK 1. Twin I Girder 2. Truss girder 10
  11. 11. TYPES OF DECK 3. box girder 4. Orthotropic girder 11
  12. 12. CABLE  A cable may be composed of one or more structural ropes, structural strands, locked coil strands or parallel wire strands.  A strand is an assembly of wires formed helically around centre wire in one or more symmetrical layers.  A strand can be used either as an individual load-carrying member, where radius or curvature is not a major requirement, or as a component in the manufacture of the structural rope.  A rope is composed of a plurality of strands helically laid around a core. In contrast to the strand, a rope provides increased curvature capability and is used where curvature of the cable becomes an important consideration. 12
  13. 13. TYPES OF CABLE 13 PROPERTIES OF CABLES
  14. 14. 14 Cables are made of high-strength steel, usually encased in a plastic or steel covering that is filled with grout , a fine grained form of concrete, for protection against corrosion.
  15. 15. SELECTION OF CABLE CONFIGURATION  The selection of cable configuration and number of cables is dependent mainly on length of the span, type of loadings, number of roadway lanes, height of towers, and the designer’s individual sense of proportion and aesthetics.  Cost also plays important role in deciding the selection.  Using less number of cables increases concentrated load at a single point thereby requiring additional reinforcement for the deck slab as well as pylon . 15
  16. 16. POSITIONS OF THE CABLES IN SPACE  Two plane system  Two Vertical Planes System  Two Inclined Planes System  The Single Plane System 16
  17. 17. TWO VERTICAL PLANES SYSTEM  In this type of system there are two parallel sets of cables and the tower on the either sides of the bridge, which lie in the same vertical plane. 1. The cable anchorages may be situated outside the deck structure, which is better than the other in terms of space as no deck area of the deck surface is obstructed by the presence of the cables and the towers. 2. but this requires substantial cantilevers to be constructed in order to transfer the shear and the bending moment into the deck structure.  When the cables and tower lie within the cross-section of the bridge, the area taken up cannot be utilized as a part of the roadway and may be only partly used for the sidewalk. Thus as area of the deck surface is made non-effective and has to be compensated for by increasing overall width of the deck. 17
  18. 18. TWO INCLINED PLANES SYSTEM  In this system the cables run from the edges of the bridge deck to a point above the centreline of the bridge on an A-shaped tower or λ-shaped or diamond shaped pylon.  This arrangement can be recommended for very long spans where the tower has to be very high and needs the lateral stiffness given by the triangle and the frame junction. 18
  19. 19. THE SINGLE PLANE SYSTEM  This type of system consists of bridges with only one vertical plane of stay cables along the middle longitudinal axis of the superstructure  As the cables are located in a single centre vertical strip thus all the space is utilized by the traffic.  This system also creates a lane separation as a natural continuation of the highway approaches to the bridge.  longitudinal arrangements of the cables used with two planes bridges are also applied to single centre girder bridges. 19
  20. 20. CABLE ANCHORAGE 20  Anchorage at concrete
  21. 21. CABLE ANCHORAGE  Anchorage at concrete 21
  22. 22. 22 CABLE ANCHORAGE  Anchorage at steel
  23. 23. 23 CABLE ANCHORAGE  Anchorage at steel
  24. 24. 24 CABLE ANCHORAGE  Anchorage at steel
  25. 25. 25 CABLE ANCHORAGE  Anchorage at steel
  26. 26. 26 INSTALLATION OF CABLES ANCHORAGE 1. Unreeling on carriages 2. Connecting the tensioning rod 3. Pulling into anchorage 4. Fixing the anchorage at the tower head 5. Installation at girder 6. Cable tensioning 7. Final anchorage 8. Delivery of strands 9. Supply PE pipes 10. Scaffolding at tower head 11. Anchor heads at the tower 12. Aligning PE pipes on bridge deck 13. Fusion welding of PE pipes 14. PE pipe with lifting collar
  27. 27. 27 1. Strand pulled through the stay pipe INSTALLATION OF CABLES ANCHORAGE
  28. 28. 28 2. Temporary connection of the stay pipe at tower INSTALLATION OF CABLES ANCHORAGE
  29. 29. INSTALLATION OF CABLES ANCHORAGE 29 3. Deformations influencing cable lengths
  30. 30. INSTALLATION OF CABLES ANCHORAGE 30 4. Mono jack for stressing individual strands
  31. 31. INSTALLATION OF CABLES ANCHORAGE 31 5. Stressing of individual strands
  32. 32. INSTALLATION OF CABLES ANCHORAGE 32 6. Stay cable without deviator and anti-vandalism pipe
  33. 33. INSTALLATION OF CABLES ANCHORAGE 33 7. Protruding strands for re-stressing
  34. 34. INSTALLATION OF CABLES ANCHORAGE 34 8. Multi-strand jack for stressing complete cable
  35. 35. INSTALLATION OF CABLES ANCHORAGE 35 9. Stressing of complete cable
  36. 36. INSTALLATION OF CABLES ANCHORAGE 36 10. Power seating of the wedges
  37. 37. INSTALLATION OF CABLES ANCHORAGE 37 11. Dampers inside boots and anti-vandalism pipes
  38. 38. INSTALLATION OF CABLES ANCHORAGE 38 12. Corrosion-protection paint and strand cap
  39. 39. BRIDGE BEARINGS 39
  40. 40. FUNCTION OF BEARINGS  Bridge bearings are used to transfer forces from the superstructure to the substructure, allowing the following types of movements of the superstructure:  Translational movements; and  Rotational movements Until the middle of this century, the bearings used consisted of following types:  Pin  Roller  Rocker  Metal sliding bearings 40
  41. 41. PIN BEARING  A pin bearing is a type of fixed bearings that accommodates rotations through the use of a steel  Translational movements are not allowed.  The pin at the top is composed of upper and lower semicircularly recessed surfaces with a solid circular pin placed between.  Usually, there are caps at both ends of the pin to keep the pin from sliding off the seats and to resist uplift loads if required.  The upper plate is connected to the sole plate by either bolting or welding. The lower curved plate sits on the masonry plate. 41
  42. 42. PIN BEARING 42 Steel Pin • Rotational Movement is allowed • Lateral and Translational Movements are Restricted
  43. 43. ROLLER TYPE BEARINGS 43 Multiple Roller BearingSingle Roller Bearing o AASHTO requires that expansion rollers be equipped with “substantial side bars” and be guided by gearing or other means to prevent lateral movement, skewing, and creeping (AASHTO 10.29.3). o A general drawback to this type of bearing is its tendency to collect dust and debris.
  44. 44. ROCKER TYPE BEARING 44 • A rocker bearing is a type of expansion bearing that comes in a great variety. • It typically consists of a pin at the top that facilitates rotations, and a curved surface at the bottom that accommodates the translational movements • Rocker and pin bearings are primarily used in steel bridges.
  45. 45. SLIDING BEARINGS 45 • A sliding bearing utilizes one plane metal plate sliding against another to accommodate translations. • The sliding bearing surface produces a frictional force that is applied to the superstructure, substructure, and the bearing itself. • To reduce this friction force, PTFE (polytetrafluoroethylene) is often used as a sliding lubricating material. PTFE is sometimes referred to as Teflon, named after a widely used brand of PTFE
  46. 46. SLIDING BEARINGS 46 • Sliding Bearings be used alone or more often used as a component in other types of bearings • Pure sliding bearings can only be used when the rotations caused by the deflection at the supports are negligible. They are therefore limited to a span length of 15 m or less by ASHTTO [10.29.1.1]
  47. 47. KNUCKLE PINNED BEARING 47 • It is special form of Roller Bearing in which the Knuckle pin is provided for easy rocking. A knuckle pin is inserted between the top and bottom casting. The top casting is attached to the Bridge superstructure, while the bottom casting rests on a series of rollers • Knuckle pin bearing can accommodate large movements and can accommodate sliding as well as rotational movement
  48. 48. POT BEARINGS 48
  49. 49. POT BEARINGS  A POT BEARING consists of a shallow steel cylinder, or pot, on a vertical axis with a neoprene disk which is slightly thinner than the cylinder and fitted tightly inside.  A steel piston fits inside the cylinder and bears on the neoprene.  Flat brass rings are used to seal the rubber between the piston and the pot.  The rubber behaves like a viscous fluid flowing as rotation may occur.  Since the bearing will not resist bending moments, it must be provided with an even bridge seat. 49
  50. 50. PLAIN ELASTOMERIC BEARINGS 50
  51. 51. LAMINATED ELASTOMERIC BEARINGS 51 Elastomeric material interspersed with steel plates
  52. 52. LAMINATED ELASTOMERIC BEARINGS 52 o consist of a laminated elastomeric bearing equipped with a lead cylinder at the center of the bearing. o The function of the rubber-steel laminated portion of the bearing is to carry the weight of the structure and provide post- yield elasticity. o The lead core is designed to deform plastically, thereby providing damping energy dissipation. o Lead rubber bearings are used in seismically active areas because of their performance under earthquake loads.
  53. 53. SELECTION OF BEARING TYPE ACCORDING TO AASHTO 53 Long Trans Long Trans Vert Long Trans Vert S L R U L L S S L L L L 2 6 0 0 18 S S S S L L L L 4 4 0 0 20 U U U U U L L S 1 2 0 5 7 S S S S L L L S 5 3 0 0 21 S S U U S R R S 4 0 2 2 14 R R S S S R R S 4 0 4 0 16 R R U S U R R S 2 0 4 2 10 R R S S L S R S 4 1 3 0 17 R R S S U R R S 3 0 4 1 13 R R S S L S S S 5 1 2 0 19 S U U S U U R S 3 0 1 4 10 U U U S U S R S 3 0 1 4 10 S U U S U U R S 3 0 1 4 10 S U U U U U U S 2 0 0 6 6 Score Rank Type of Bearing S = suitable, U = unsuitable, L = suitable for limited applications, R = may be suitable, but requires special considerations or additional elements such as slider or guideways. Bearing Suitability: Disk bearing Pot bearing Rocker bearing AASHTO Table 14.6.2-1 Axis indicated Single roller bearing Multiple roller bearing Rotation about bridge Resistance to Loads Curved sliding spherical bearing Curved sliding cylindrical bearing Double cylindrical bearing Knuckle pinned bearing Fiberglass reinforced pad Cotton duck reinforced pad Steel-reinforced elastomeric bearing Plane sliding bearing Movement Plain elastomeric pad
  54. 54. TESTS ON CABLE STAYED BRIDGE MODEL 54 1. Wind Tunnel Test 2. FatigueTest 3. TENSILE LOAD TEST OF THE STRAND 4. INSPECTION OF ANCHORAGES 5. CHECKING HARDNESS OF WEDGES 6. ROTATIVE FLEXION TEST
  55. 55. OUR PROJECT DEFINITION  We have three spans (120+250+120) m  The deck at the height of (50) m clearance  We have (80) Cables are arranged in a double plane over the bridge length with (12) m spacing. 55
  56. 56. COMPONENTS 1. Pylon We have two non-prismatic pylons ,each one have (130 m) height. 56
  57. 57. COMPONENTS 2. Deck  Width = 28 m  Consists of (6) lanes  (3) lanes in each direction With width (3.6)m  An intermediate island (1)m width  (2) side walk each one (2.7)m width 57
  58. 58. COMPONENTS 2. Deck  Consists of  2 Main I girder 2.8 depth of thickness 2 cm and 2 flanges 60 cm width with thickness 5 cm.  X-girders 2.8 depth of thickness 2 cm and 2 flanges 50 cm width with thickness 5 cm.  Stringers with IPE#600 section.  Concrete Slab of thickness 20 cm Fcu=400 kg/cm2 and 7cm Bitumious asphalt. 58
  59. 59. COMPONENTS 3. Cables  We have (10) cables in each side of the pylon.  The cables have initial diameter (12)cm.  The distance between cables in the deck plan equals to (12) m.  The distance between them at its links to the pylon equals to (1.5) m 59
  60. 60. MODELING STEPS (USING CSI SAP2000 PROGRAM ) 60

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