Advantages of continous members
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Advantages of continous members

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prestress concrete

prestress concrete

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Advantages of continous members Advantages of continous members Presentation Transcript

  • TOPIC 1ADVANTAGES OF CONTINOUSMEMBERS
  • EVEN DISTRIBUTION OF MOMENTS• Between center of span and supports• Lesser span moments• Longer spans
  • REDUCTION OF SIZE• Vertical load carrying capacity is more• Lighter structures• Economical
  • HIGHER LOAD CARRYING CAPACITY• Redistribution of moments• Reduced cross sectional dimensions
  • INCREASED STABILITY• Redundancy in load path• Formation of hinges in extreme events
  • PRECAST UNITS CONNECTED BY PRESTRESSED CABLES• Segmental construction• Precast units• Connected by pre-stressed cable
  • SUITABLE POSITIONING OF CURVED CABLES• In post tensioned girders• Resist span and support moments
  • REDUCTION IN NO: OF ANCHORAGES• One pair of post tensioned anchorages• A single stressing operation• Less maintenance
  • SMALLER DEFLECTIONS• Higher load carrying capacity• Even distribution of moments• Safer
  • DISADVANTAGES• Secondary stresses• Losses• Skill of workmanship• Analysis and design• Concordant cables
  • TOPIC 2METHODS OF ACHIEVINGCONTINUITY
  • USING STRAIGHT CABLES• Wide web necessary• Large anchorage blocks• Form work• Skilled workmen• High strength threaded rods
  • USING CURVED CABLES• Higher resistance to stress• Longer spans• Cracking over piers eliminated in multistage post-tensioning
  • USING CAP CABLESNegative moment taken care of
  • USING STRAIGHT TENDONSLimited length
  • COMPOSITE CONSTRUCTION• Beam ends embedded in cast-in-situ diaphragms• Reinforcement for negative moment within deck thickness• SS under major loads
  • COUPLING• Pre-tensioned precast members• Optimized strands• Top strands at adjacent interior members coupled• Performance of full length post tensioning• Lesser cost
  • 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
  • TOPIC 3EFFECT OF PRESTRESS