Advantages of continous members

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prestress concrete

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Advantages of continous members

  1. 1. TOPIC 1ADVANTAGES OF CONTINOUSMEMBERS
  2. 2. EVEN DISTRIBUTION OF MOMENTS• Between center of span and supports• Lesser span moments• Longer spans
  3. 3. REDUCTION OF SIZE• Vertical load carrying capacity is more• Lighter structures• Economical
  4. 4. HIGHER LOAD CARRYING CAPACITY• Redistribution of moments• Reduced cross sectional dimensions
  5. 5. INCREASED STABILITY• Redundancy in load path• Formation of hinges in extreme events
  6. 6. PRECAST UNITS CONNECTED BY PRESTRESSED CABLES• Segmental construction• Precast units• Connected by pre-stressed cable
  7. 7. SUITABLE POSITIONING OF CURVED CABLES• In post tensioned girders• Resist span and support moments
  8. 8. REDUCTION IN NO: OF ANCHORAGES• One pair of post tensioned anchorages• A single stressing operation• Less maintenance
  9. 9. SMALLER DEFLECTIONS• Higher load carrying capacity• Even distribution of moments• Safer
  10. 10. DISADVANTAGES• Secondary stresses• Losses• Skill of workmanship• Analysis and design• Concordant cables
  11. 11. TOPIC 2METHODS OF ACHIEVINGCONTINUITY
  12. 12. USING STRAIGHT CABLES• Wide web necessary• Large anchorage blocks• Form work• Skilled workmen• High strength threaded rods
  13. 13. USING CURVED CABLES• Higher resistance to stress• Longer spans• Cracking over piers eliminated in multistage post-tensioning
  14. 14. USING CAP CABLESNegative moment taken care of
  15. 15. USING STRAIGHT TENDONSLimited length
  16. 16. COMPOSITE CONSTRUCTION• Beam ends embedded in cast-in-situ diaphragms• Reinforcement for negative moment within deck thickness• SS under major loads
  17. 17. COUPLING• Pre-tensioned precast members• Optimized strands• Top strands at adjacent interior members coupled• Performance of full length post tensioning• Lesser cost
  18. 18. TWO TYPES PARTIALLYFULLY CONTINOUS CONTINOUS • Using cap cables• Using straight cables • Using straight tendons• Using curved cables • Tendons not used to• Larger size tendons achieve continuity • Negative moment at• Secondary reinforcements supports• Expensive • Cheaper
  19. 19. TOPIC 3EFFECT OF PRESTRESS

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