Residual capacity from aggregate interlock        Case: cracked concrete slab bridge   11-07-2012Eva Lantsoght, Cor van de...
Introduction (1)• 50-year-old concrete slab bridge with  traffic restrictions• Extensive cracking in southern  concrete ap...
flexural                     through crackIntroduction (2)                                d = 413mm (side) to 493mm (mid) ...
through crackAggregate interlock• Aggregates stronger than cement paste• Particles interlock with opposite face + resist s...
Calculations (1)Shear & Aggregate interlock• Shear capacity (inclined cracking load)• VVBC = 273 kN/m (side) and 325 kN/m ...
Calculations (2)Maximum crack width (1)• Relation between w and aggregate interlock capacity• Expressions for unreinforced...
Calculations (3)Maximum crack width (2)• Find: crack width Vu_unr < VVBC or Fax < Fclamp                                  ...
Calculations (4)Axial force equilibrium•   wmax ~ rebar, tension in concrete cross-section (vary % Ftc)•   Requirement: Va...
Proposed actions + Conclusions• Replace rusted steel bearings by elastomeric bearings• Open bridge for all traffic• Quanti...
Contact:Eva LantsoghtE.O.L.Lantsoght@tudelft.nl+31(0)152787449                Residual capacity from aggregate interlock o...
Upcoming SlideShare
Loading in...5
×

Residual capacity from aggregate interlock

2,071

Published on

Published in: Education, Business, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
2,071
On Slideshare
0
From Embeds
0
Number of Embeds
26
Actions
Shares
0
Downloads
4
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Transcript of "Residual capacity from aggregate interlock"

  1. 1. Residual capacity from aggregate interlock Case: cracked concrete slab bridge 11-07-2012Eva Lantsoght, Cor van der Veen, Joost Walraven Delft University of Technology Challenge the future
  2. 2. Introduction (1)• 50-year-old concrete slab bridge with traffic restrictions• Extensive cracking in southern concrete approach bridge• Result of settlement• Flexural reinforcement yielded at crack• Cores: C33/45• Reinforcement QR 240:fyd =209 MPa; εsu = 19% – 38% Residual capacity from aggregate interlock of cracked concrete slab bridge 2
  3. 3. flexural through crackIntroduction (2) d = 413mm (side) to 493mm (mid) φbottom 14mm – 200mm φtop 25mm – 100mm Residual capacity from aggregate interlock of cracked concrete slab bridge 3
  4. 4. through crackAggregate interlock• Aggregates stronger than cement paste• Particles interlock with opposite face + resist shear displacement• Contribution to shear capacity: 33% - 90%• Slab bridge, 1% rebar: aggregate interlock is main shear carrying mechanism• Fundamental model by Walraven• Shear + axial stress: σ & τ, ∆ & w• Unreinforced sections: crack-opening• Reinforced sections: capacity Residual capacity from aggregate interlock of cracked concrete slab bridge 4
  5. 5. Calculations (1)Shear & Aggregate interlock• Shear capacity (inclined cracking load)• VVBC = 273 kN/m (side) and 325 kN/m (mid)• Aggregate interlock – no tension on cross-section• Based on shear stress capacity τ of reinforced crack• Plain reinforcement => 0.5ρl• Vagg = 1575 kN/m (side) and 1679 kN/m (mid)• Large resistance provided by aggregate interlock action• Rusted bearings => deformation due to ∆T is restrained• Conservative assumption: full concrete cross-section in tension Fclamp   As ,bottom  As ,top  f y  f ctk d i b Residual capacity from aggregate interlock of cracked concrete slab bridge 5
  6. 6. Calculations (2)Maximum crack width (1)• Relation between w and aggregate interlock capacity• Expressions for unreinforced section• Based on graph (Walraven, 1981): Δ = 1.25w Residual capacity from aggregate interlock of cracked concrete slab bridge 6
  7. 7. Calculations (3)Maximum crack width (2)• Find: crack width Vu_unr < VVBC or Fax < Fclamp wmax ≈ 1 mm Residual capacity from aggregate interlock of cracked concrete slab bridge 7
  8. 8. Calculations (4)Axial force equilibrium• wmax ~ rebar, tension in concrete cross-section (vary % Ftc)• Requirement: Vagg ≥ 2VVBC• Find associated ∆• Find Nagg(wmax,∆) (clamping effect)• Remaining capacity of top reinforcement to resist tension: Ntension = As,topfy – Nagg• Compare to Ftc => Equilibrium?• Result: maximum 71% of restraint Residual capacity from aggregate interlock of cracked concrete slab bridge 8
  9. 9. Proposed actions + Conclusions• Replace rusted steel bearings by elastomeric bearings• Open bridge for all traffic• Quantify amount of restraint through measurements at support• Measurement points for cracks every 3m (lane width)• Special cases: use aggregate interlock to check cracked cross- sections in shear• Quantifies residual bearing capacity• Shear and axial compression Residual capacity from aggregate interlock of cracked concrete slab bridge 9
  10. 10. Contact:Eva LantsoghtE.O.L.Lantsoght@tudelft.nl+31(0)152787449 Residual capacity from aggregate interlock of cracked concrete slab bridge 10
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×