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Time-depended Behavior of Prestressed Concrete Members

Time-depended Behavior of Prestressed Concrete Members. Prof. Kokalanov Gorgi Asist. Markovski Goran Asist. Mihajlov Vikotr Faculty of Civil Engineering, Skopje, Macedonia. An influence of live load under time-dependent behavior of prestressed concrete members is considered .

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Time-depended Behavior of Prestressed Concrete Members

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  1. Time-depended Behavior of Prestressed Concrete Members Prof. Kokalanov Gorgi Asist. Markovski Goran Asist. Mihajlov Vikotr Faculty of Civil Engineering, Skopje, Macedonia CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  2. An influence of live load under time-dependent behavior of prestressed concrete members is considered. The experimental program includes 3 series ( A, B ,V) of prestressed concrete simple beams with dimensions 15/28 cm and L=2,80 m span. There are 4 groups of beams in each series. CAD BUREAU Computer Added Bureau, Skopje, Macedonia

  3. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  4. Time-dependent behavior of prestressed concrete members prestressed at t=30days • First group beams were testing at short - time load until breaking at t=40 days. • Second group will be tested until breaking at t=400 days. • Third group  after 10 days of prestressing two concentrated forces are applied. There is no cracking. These beams are under sustained load for 360 days. • Fourth group beams with same sustained load as third plus cyclic live load (two concentrated forces). These forces act at time steps of 12 hours (12 hours Fg+Fp, another 12 hours only Fg). The load ( Fg+Fp) is sufficient to produce cracking. CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  5. Time-dependent behavior of prestressed concrete members Mathematical Model • The beam is divided into 30 shell (QUAD) elements. • The elements are divided into 20 layers. For each layer, the allowable stresses are obtained from the strain-distribution of the pure concrete with the lower value value of tensile strength FCTK. The compression stresses is limited as well due the relation of the principle stresses. The steel forces include tension stiffening effect. CAD BUREAU Computer Added Bureau, Skopje, Macedonia

  6. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  7. Time-dependent behavior of prestressed concrete members Material concrete FC = maximum uniaxial pressure FCT = average tensile strength fuer tension stiffening FCTK = lower value of tensile strength for pure concrete The biaxial compression stress is limited due to the relation of the principal stresses: Biaxial behavior acc. Kupfer-Hilsdorf-Rüsch acc. to the relation of the principal stresses CAD BUREAU Computer Added Bureau, Skopje, Macedonia

  8. Time-dependent behavior of prestressed concrete members With the obtained max. value of beta-ic a uniaxial stress-strain-relation is built for each layer and each element: Uniaxial stress-strain-relation in case of compression Tension is limited in both principal stress directions to beta-z: Uniaxial stress-strain-relation for tension CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  9. Time-dependent behavior of prestressed concrete members Material steelStandard is a bilinear stress-strain-relation with yield limitation. Trilinear relation is possible within a manual input: The tension stiffening effect is included according Eurocode 2 and results in a crack-width wk,cal: wk,cal = 1.7  amsm CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  10. Time-dependent behavior of prestressed concrete members • Creep and shrincage • Concrete creep-strains are calculated with a rough method of decreasing the concrete modulus of elasticity • E-creep = E-linear * 1/(1+phi) • with a total creep value phi. • The modulus of elasticity of the steel is not changed. • Shrincage is analized with a strain-load that acts only on the concrete and not on the reinforcement. CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  11. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  12. Time-dependent behavior of prestressed concrete members Tensilestrength Tension Bending PAB/87 CEB-FIP MC90 CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  13. Time-dependent behavior of prestressed concrete members Tensilestrength • Experimentally: • Prof. D. Ivanov, Faculty of Civil Engineering, Skopje • Reference: • Concrete Society Technical Report N0 23 • Partially prestressing • Report of a Concrete Society • Working Party. • The stress of which cracking becomes visible corresponds approximately to the modules of rupture (normal tensile strength due to bending of unreinforcement concrete) • It is about twice the tensile strength of the concrete. CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  14. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  15. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  16. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  17. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  18. Time-dependent behavior of prestressed concrete members Bridge Zdunje L=358m, H=63.89 CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  19. Time-dependent behavior of prestressed concrete members Cross Sections Support Midspan Column CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  20. Time-dependent behavior of prestressed concrete members Construction Stage 1 CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  21. Time-dependent behavior of prestressed concrete members Construction Stage 9 CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  22. Time-dependent behavior of prestressed concrete members CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  23. Time-dependent behavior of prestressed concrete members Dead Load CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  24. Time-dependent behavior of prestressed concrete members Prestresses forces CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  25. Time-dependent behavior of prestressed concrete members Equipment CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  26. Time-dependent behavior of prestressed concrete members Additional Load CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  27. Time-dependent behavior of prestressed concrete members D. Displacement – dead load CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  28. Time-dependent behavior of prestressed concrete members P. Displacement – prestressed forces CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  29. Time-dependent behavior of prestressed concrete members E. Displacement – equipment CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  30. Time-dependent behavior of prestressed concrete members A. Displacement – additional loads CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  31. Time-dependent behavior of prestressed concrete members C. Displacement - creep CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

  32. Time-dependent behavior of prestressed concrete members Displacement (D+P+E+A) / (D+P+E+A+C) CAD BUREAU – Computer Added Bureau, Skopje, Macedonia

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