Advantages of continous members

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    21-Jan-2015
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prestress concrete

Transcript of Advantages of continous members

  • 1. TOPIC 1ADVANTAGES OF CONTINOUSMEMBERS

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