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Shear tests of RC slabs and slab stripsunder concentrated loads Eva Lantsoght 23-07-2012          Delft          Universit...
Overview• Introduction   • Project description   • Previous research• Experiments   • Setup   • Specimens   • Results• Res...
Background      Project description (1)                   Shear failure of the de la Concorde bridge, LavalThe Netherlands...
BackgroundProject description (2)• Capacity of existing bridges in NL   • TU Delft      • Concrete Structures      • Struc...
Background       Project description (3)• Concrete Structures   •   Long-term tensile strength (C-1.4)   •   Beam shear – ...
BackgroundShear and punching (1)   Beam shear, one-way shear                            Punching shear, two-way shear• Pun...
BackgroundShear and punching (2)    45 load spreading                       45 load spreading – French practice    Shear t...
BackgroundPrevious research (1)• Database: 207 tests slabs and wide beams in shear• a/d = 0,65 – 9,8• Different categories...
Background      Previous research (2)• Recent research: slabs under line loads• From database: 22   • Concentrated load   ...
Goals•   Assess shear capacity of slabs    under concentrated loads•   Determine effective width in    shear    Shear test...
ExperimentsExperimental setup Size: 5m x 2,5m (variable) x 0,3m Continuous support, Line supports Load: vary a/d and posit...
Experimental results   Experimental setup (2)• Distance between load and support(a/d = 1,51 and a/d = 2,26)• Simple or con...
ResultsEffective width (1) 0         500          1000          1500          2000          2500                          ...
ResultsEffective width (2)    Shear tests of reinforced concrete slabs and slab strips under concentrated loads   14
ResultsEffective width (3)    Shear tests of reinforced concrete slabs and slab strips under concentrated loads   15
ResultsEffective width (4)    Shear tests of reinforced concrete slabs and slab strips under concentrated loads   16
ResultsComparison to design models (1)• EN 1992-1-1:2005   • Shear governing over punching   • Two load spreading methods ...
Results     Comparison to design models (2)Best results: beff2 and Regan’s method            Shear tests of reinforced con...
Results  Comparison to design models (3)beff2 better results than beff1=> smaller range of AVG=> better COV           Shea...
Results  Comparison to design models (4)Ribbed bars vs. plain barsPlain bars: slightly smaller capacity≠ literature!      ...
ResultsComparison to NLFEA• Sensitive to input  parameters• Compared to effective width• beff2 compares best       Shear t...
Recommendations• Evaluating existing solid slab bridges:   • EN 1992-1-1:2005   • Effective width: French method, min 4d  ...
Conclusions• Transverse load redistribution   • Larger shear capacity in slabs   • Enhancement factor 1,25• French load sp...
Contact:Eva LantsoghtE.O.L.Lantsoght@tudelft.nl+31(0)152787449             Shear tests of reinforced concrete slabs and sl...
ExperimentsProperties of slabs (1)    Shear tests of reinforced concrete slabs and slab strips under concentrated loads   25
Experiments  Properties of slabs (2)Test      SS/CS           Pu (kN)       Failure mode           Fpres            Vmax  ...
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Shear tests of reinforced concrete slabs and slab strips under concentrated loads

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Presentation from fib PhD symposium in Karslruhe

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Shear tests of reinforced concrete slabs and slab strips under concentrated loads

  1. 1. Shear tests of RC slabs and slab stripsunder concentrated loads Eva Lantsoght 23-07-2012 Delft University of Technology Challenge the future
  2. 2. Overview• Introduction • Project description • Previous research• Experiments • Setup • Specimens • Results• Results • Overall width/Effective width • Comparison to Code methods S9T6 at failure • Comparison to NLFEA• Conclusions Shear tests of reinforced concrete slabs and slab strips under concentrated loads 2
  3. 3. Background Project description (1) Shear failure of the de la Concorde bridge, LavalThe Netherlands: 60% of bridges built before 1975Traffic volume and loads have increased => Loads? Shear Capacity??? Shear tests of reinforced concrete slabs and slab strips under concentrated loads 3
  4. 4. BackgroundProject description (2)• Capacity of existing bridges in NL • TU Delft • Concrete Structures • Structural Mechanics • TNO • RWS• 3715 relevant structures• 2020 built before 1976• Study: bridge categories and specific details Highways in the Netherlands Shear tests of reinforced concrete slabs and slab strips under concentrated loads 4
  5. 5. Background Project description (3)• Concrete Structures • Long-term tensile strength (C-1.4) • Beam shear – sustained loads (A-1.2) • Continuous girders – shear (A-1.2) • Prestressed slabs – CMA (A-1.5) • Slab bridges - shear/punching Concrete bridges Shear tests of reinforced concrete slabs and slab strips under concentrated loads 5
  6. 6. BackgroundShear and punching (1) Beam shear, one-way shear Punching shear, two-way shear• Punching shear over perimeter around load• Beam shear formulas over effective width at support• Effective width? Shear tests of reinforced concrete slabs and slab strips under concentrated loads 6
  7. 7. BackgroundShear and punching (2) 45 load spreading 45 load spreading – French practice Shear tests of reinforced concrete slabs and slab strips under concentrated loads 7
  8. 8. BackgroundPrevious research (1)• Database: 207 tests slabs and wide beams in shear• a/d = 0,65 – 9,8• Different categories • simply supported slab • continuous slab • real bridge • cantilever• Failure mode based on pictures/ crack patterns: WB/P Shear tests of reinforced concrete slabs and slab strips under concentrated loads 8
  9. 9. Background Previous research (2)• Recent research: slabs under line loads• From database: 22 • Concentrated load • a/d < 2,5 • Small: d < 15cm• Comparison to EC2 • Evidence for additional capacity • Experiments on larger specimens needed Shear tests of reinforced concrete slabs and slab strips under concentrated loads 9
  10. 10. Goals• Assess shear capacity of slabs under concentrated loads• Determine effective width in shear Shear tests of reinforced concrete slabs and slab strips under concentrated loads 10
  11. 11. ExperimentsExperimental setup Size: 5m x 2,5m (variable) x 0,3m Continuous support, Line supports Load: vary a/d and position along width Shear tests of reinforced concrete slabs and slab strips under concentrated loads 11
  12. 12. Experimental results Experimental setup (2)• Distance between load and support(a/d = 1,51 and a/d = 2,26)• Simple or continuous support• Amount of transverse flexural reinforcement• Reinforcement type: plane or ribbed bars• Size of the loading plate• Type of support: line support or bearing• Concrete compressive strength BS2T1• Loading in the middle of width or near edge• Total width First series: 30 specimens, 133 experiments Shear tests of reinforced concrete slabs and slab strips under concentrated loads 12
  13. 13. ResultsEffective width (1) 0 500 1000 1500 2000 2500 b (mm) Specimens with different widths: threshold value observed Shear tests of reinforced concrete slabs and slab strips under concentrated loads 13
  14. 14. ResultsEffective width (2) Shear tests of reinforced concrete slabs and slab strips under concentrated loads 14
  15. 15. ResultsEffective width (3) Shear tests of reinforced concrete slabs and slab strips under concentrated loads 15
  16. 16. ResultsEffective width (4) Shear tests of reinforced concrete slabs and slab strips under concentrated loads 16
  17. 17. ResultsComparison to design models (1)• EN 1992-1-1:2005 • Shear governing over punching • Two load spreading methods • CRd,c = 0,15• French NA • Larger vmin for slabs • French load spreading method• Regan’s method • Based on punching perimeter • # sides ~ width • Enhancement close to support • Enhancement for CS Shear tests of reinforced concrete slabs and slab strips under concentrated loads 17
  18. 18. Results Comparison to design models (2)Best results: beff2 and Regan’s method Shear tests of reinforced concrete slabs and slab strips under concentrated loads 18
  19. 19. Results Comparison to design models (3)beff2 better results than beff1=> smaller range of AVG=> better COV Shear tests of reinforced concrete slabs and slab strips under concentrated loads 19
  20. 20. Results Comparison to design models (4)Ribbed bars vs. plain barsPlain bars: slightly smaller capacity≠ literature! Shear tests of reinforced concrete slabs and slab strips under concentrated loads 20
  21. 21. ResultsComparison to NLFEA• Sensitive to input parameters• Compared to effective width• beff2 compares best Shear tests of reinforced concrete slabs and slab strips under concentrated loads 21
  22. 22. Recommendations• Evaluating existing solid slab bridges: • EN 1992-1-1:2005 • Effective width: French method, min 4d • 25% reduction of contribution concentrated load close to support • β =av/2d • Combined: βnew =av/2,5d Shear tests of reinforced concrete slabs and slab strips under concentrated loads 22
  23. 23. Conclusions• Transverse load redistribution • Larger shear capacity in slabs • Enhancement factor 1,25• French load spreading method for beff • Literature • Experiments • NLFEA• Loads close to support • Direct load transfer Shear tests of reinforced concrete slabs and slab strips under concentrated loads 23
  24. 24. Contact:Eva LantsoghtE.O.L.Lantsoght@tudelft.nl+31(0)152787449 Shear tests of reinforced concrete slabs and slab strips under concentrated loads 24
  25. 25. ExperimentsProperties of slabs (1) Shear tests of reinforced concrete slabs and slab strips under concentrated loads 25
  26. 26. Experiments Properties of slabs (2)Test SS/CS Pu (kN) Failure mode Fpres Vmax Vmax,EC (kN) (kN) (kN)S11T1 SS 1194 WB + P 165 998 848S11T4 CS 958 WB + P 307 886 766S12T1 SS 931 WB + B + P 162 780 663S12T2 SS 1004 P 173 839 712S12T4 CS 773 WB + P + B 147 705 608S12T5 CS 806 WB + B 158 735 633S13T1 SS 1404 WB + P 157 1253 593S13T4 CS 1501 WB + P 240 1411 706S14T1 SS 1214 WB + P + B 133 1088 518S14T2 SS 1093 WB + P + B 162 975 462S14T4 CS 1282 WB + P + B 187 1207 605S14T5 CS 1234 WB + P + B 142 1157 578 Shear tests of reinforced concrete slabs and slab strips under concentrated loads 26

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