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Joint Types and Behavior

Joint Types and Behavior. Jointing Patterns. Joint Functions 1) Control cracking 2) Provide space and freedom of movement 3) Facilitate construction Slab Stiffness Components : Joint Thickness : shear capacity - Slab action : basin area Crack width : shear capacity

bruce-moreno
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Joint Types and Behavior

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  1. Joint Types and Behavior

  2. Jointing Patterns Rigid Pavement Design Course

  3. Joint Functions • 1) Control cracking • 2) Provide space and freedom of movement • 3) Facilitate construction • Slab Stiffness Components: Joint • Thickness : shear capacity • - Slab action : basin area • Crack width : shear capacity • Subbase/Slab interface friction • Load transfer • 1) Shear – aggregate interlock • 2) Dowel Rigid Pavement Design Course

  4. Contraction Joints • Control trans. Cracking • Formed by weakened joint • - Saw Cutting • - Grooving • - Insert Strip • - With and without dowel A B Rigid Pavement Design Course

  5. Construction Joints • Planned interruptions • Isolation joint • Transverse or Longitudinal D E Rigid Pavement Design Course

  6. Isolation Joint • Space for expansion • - temp/moisture increase • - Use compressible filler, LT or slab thickening C Rigid Pavement Design Course

  7. Longitudinal Joints • Between paving lanes • - can be a construction or contraction joint • Butt or Keyway joint • Placed with tie bar • Wide pavement sections: • - combination or tied and doweled joints Rigid Pavement Design Course

  8. Longitudinal Joints G F Dowel Bar Tie Bar H Rigid Pavement Design Course Tie Bolt

  9. Load Transfer Systems • Aggregate Interlock • Simple • Small openings • Low traffic • Wears out • Mechanical load transfer • Many designs • Round dowel bars most popular • Installed in a single row • Keyed Joints • Long. Joints; 8” slabs or greater • Tied Joints • # 4 or #5 bars; • 24” to 48” long • 18” - 48” spacing Not Recommended Bent or Threaded Z Joint Rigid Pavement Design Course

  10. Applied Wheel Load (P) 0% Load Transfer Where: Deflection of unloaded Slab Deflection of Loaded Slab Total Deflection Rigid Pavement Design Course

  11. Applied Wheel Load (P) 100% Load Transfer Rigid Pavement Design Course

  12. Load Transfer (1.0,0% LTE) 1.0 (.67,44% LTE) (.55,100% LTE) 0 Rigid Pavement Design Course

  13. Tied Shoulder Effect Slab Length (L) Single Axle Loading DowelBar s w Hinge Joint Traffic Lane Hinge Joint a Do Agg Shoulder SlabThickness he Subbase Subgrade Critical Stress forMid Slab Loading Rigid Pavement Design Course

  14. Load Transfer – Crack Width Requirements Rigid Pavement Design Course

  15. Load Transfer – Crack Width Factors Rigid Pavement Design Course

  16. Load Transfer – Crack Width Requirements:Thickness Factors Rigid Pavement Design Course

  17. Emergency Joints? Rigid Pavement Design Course

  18. 100 Joint Opening 0.025 in. 80 60 0.035 Effectiveness, percent 0.045 40 0.065 20 0.085 0 0 1 2 3 4 5 6 7 8 9 10 Loading Cycles, 100 000 Influence of Joint Opening on Effectiveness, 9 Inch Concrete Slab, 6 Inch Gravel Subbase (82) Rigid Pavement Design Course

  19. Joint Opening 0.015 in. 100 80 60 0.025 Effectiveness, percent 40 0.035 20 0.045 0.065 0 0 1 2 3 4 5 6 7 8 9 10 Loading Cycles, 100 000 Influence of Joint Opening on Effectiveness, 7 Inch Concrete Slab, 6 Inch Gravel Subbase (82) Rigid Pavement Design Course

  20. 100 0.035-in. joint opening 80 0.065-in. 60 Effectiveness, percent 0.065-in. 40 9-in. Slab 20 0 0 1 2 3 4 5 6 7 8 9 10 Loading Cycles, 100 000 Influence of joint opening on effectiveness (9 in. slab, cement stabilized subbase, k=542 pci) Rigid Pavement Design Course

  21. Functions of Subbase 1.) To Provide a stable construction platform 2.) To control the depth of frost penetration 3.) Prevent erosion of the pavement support 4.) Provide uniform slab support 5.) Facilitate drainage 6.) Provide increased slab support Rigid Pavement Design Course

  22. 60 50 40 30 20 10 0 Agg  107 Agg=106 Max. Shear Stress at Joint Interface, psi Agg=105 Agg=5x104 Agg=104 Agg=5x103 Agg=103 Agg=102 10 12 14 16 18 20 24 Effect of Slab Thickness on Maximum Shear Stresses at Joint Interface Rigid Pavement Design Course

  23. 100 80 60 40 20 0 Agg=106psi Agg=105psi Agg=5x104psi Agg=104psi Joint Eff. % Agg=5x103psi Agg=103psi Agg=102psi 0.2 0.6 1.0 1.4 1.8 2.2 2.6 3.0 3.4 10,000 Subgrade Mod. X Mod. Of Relative Stiff. , psi-1 Figure 4-18. Relation between Joint Efficiency (Eff) and Spring Stiffness (Agg) Rigid Pavement Design Course

  24. k-in. in. 144 120 96 72 48 24 0 144 120 96 72 48 24 0 Free Edge Interior Max. Tensile Edge Stress x (Slab Thickness)2, Edge W/Agg Agg=105 Agg  106 30 60 100 30 60 100 Modulus of Aggregate Stiffness, in. Effect of Aggregate Interlock in Reducing Maximum Tensile Edge Stresses Rigid Pavement Design Course

  25. k-in. in. 144 120 96 72 48 24 0 144 120 96 72 48 24 0 Max. Tensile Edge Stress x (Slab Thickness)2, Agg=104 Agg102 30 60 100 30 60 100 Modulus of Aggregate Stiffness, in. Rigid Pavement Design Course

  26. 0.12 0.10 0.08 0.06 0.04 0.02 0 0.12 0.10 0.08 0.06 0.04 0.02 0 Agg  106 Agg=105 Max. Edge Deflection, in. Free Edge Edge W/Agg Interior 0 0.08 0.16 0.24 0.32 0 0.08 0.16 0.24 0.32 Load , in. Subgrade Mod. x (Mod. Of Relative Stiff.)2 Effect of Aggregate Interlock in Reducing Maximum Edge Deflection Rigid Pavement Design Course

  27. 0.12 0.10 0.08 0.06 0.04 0.02 0 0.12 0.10 0.08 0.06 0.04 0.02 0 Agg=104 Agg102 Max. Edge Deflection, in. 0 0.08 0.16 0.24 0.32 0 0.08 0.16 0.24 0.32 Load , in. Subgrade Mod. x (Mod. Of Relative Stiff.)2 Rigid Pavement Design Course

  28. P=200 lb/in. 16 " 60 " 45" 45" A Typical Finite-Element Mesh Used for Analysis of Keyed Joints Rigid Pavement Design Course

  29. 0 0 0 P=200 psi 0 50 100 150 200 12" 12" Esub = 10,000 psi 3002001000 400350300 20015010050 200 150 100 50 Tensile Stress Contours for a Standard Key on a 10 in. Cement Stabilized Base Rigid Pavement Design Course

  30. StandardKey Large Key Deep Key 0.2h 0.2h 0.4h 0.1h 0.2h 483 651 822 0.1h Scale 0 100 200 300 Pounds / in. Distribution of Nodal Forces Normal to the Contact Boundaries for Different Key Designs Rigid Pavement Design Course

  31. Round Smooth Key Round Key 0.2h h 0.2h 0.1h 0.1h 859 1409 Scale 0 100 200 300 Pounds / in. Rigid Pavement Design Course

  32. Effect of Key Design on Maximum Tensile Stress in the Slab* * Slab thickness was 16 in. (40.6 cm) Rigid Pavement Design Course

  33. 12" 12" (b) Tied Joint with Aggregate Interlock (a) Doweled Joint 12" 4" (c) Joint With Aggregate Interlock On Stab. Base Rigid Pavement Design Course Figure 4-37. Possible Joint Designs for the Example Problem

  34. 12" 6" (d) Butt Joint on Stab. Base 16" 12" (f) Butt Joint (e) Thickened Edge Joint Figure 4-37. Continued Rigid Pavement Design Course

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