Joint Types and Behavior

Rigid Pavement Design Course Jointing Patterns

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

Rigid Pavement Design Course Construction Joints Planned interruptions Isolation joint Transverse or Longitudinal ED

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

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

Rigid Pavement Design Course 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 Bent or Threaded Z Joint Not Recommended Tied Joints # 4 or #5 bars; 24” to 48” long 18” - 48” spacing

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

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

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

Rigid Pavement Design Course Dowel Bar Subgrade Critical Stress for Mid Slab Loading Slab Thickness Slab Length (L) Single Axle Loading Agg Subbase hehe w s a Traffic Lane Shoulder Hinge Joint DoDo Tied Shoulder Effect

Rigid Pavement Design Course Load Transfer – Crack Width Requirements

Rigid Pavement Design Course Load Transfer – Crack Width Factors

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

Rigid Pavement Design Course Emergency Joints?

Rigid Pavement Design Course Effectiveness, percent Loading Cycles, Influence of Joint Opening on Effectiveness, 9 Inch Concrete Slab, 6 Inch Gravel Subbase (82) Joint Opening in.

Rigid Pavement Design Course Effectiveness, percent Loading Cycles, Influence of Joint Opening on Effectiveness, 7 Inch Concrete Slab, 6 Inch Gravel Subbase (82) Joint Opening in.

Rigid Pavement Design Course Influence of joint opening on effectiveness (9 in. slab, cement stabilized subbase, k=542 pci) Loading Cycles, Effectiveness, percent in. Slab in in. joint opening

Rigid Pavement Design Course 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 Effect of Slab Thickness on Maximum Shear Stresses at Joint Interface Max. Shear Stress at Joint Interface, psi Agg  10 7 Agg=10 6 Agg=10 5 Agg=5x10 4 Agg=10 4 Agg=5x10 3 Agg=10 3 Agg=10 2

Rigid Pavement Design Course Joint Eff. % 10,000 Subgrade Mod. X Mod. Of Relative Stiff., psi -1 Figure Relation between Joint Efficiency (Eff) and Spring Stiffness (Agg) Agg=10 6 psi Agg=10 5 psi Agg=5x10 4 psi Agg=10 4 psi Agg=5x10 3 psi Agg=10 3 psi Agg=10 2 psi

Rigid Pavement Design Course Modulus of Aggregate Stiffness, in. Effect of Aggregate Interlock in Reducing Maximum Tensile Edge Stresses Max. Tensile Edge Stress x (Slab Thickness) 2, k-in. in. Free Edge Interior Edge W/Agg Agg  Agg=

Rigid Pavement Design Course Agg= Modulus of Aggregate Stiffness, in. Max. Tensile Edge Stress x (Slab Thickness) 2, k-in. in. Agg  10 2

Rigid Pavement Design Course Effect of Aggregate Interlock in Reducing Maximum Edge Deflection Load Subgrade Mod. x (Mod. Of Relative Stiff.) 2, in. Max. Edge Deflection, in Free Edge Interior Edge W/Agg Agg  10 6 Agg=10 5

Rigid Pavement Design Course Agg=10 4 Agg  10 2 Max. Edge Deflection, in. Load Subgrade Mod. x (Mod. Of Relative Stiff.) 2, in.

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

Rigid Pavement Design Course Tensile Stress Contours for a Standard Key on a 10 in. Cement Stabilized Base P=200 psi 12" E sub = 10,000 psi

Rigid Pavement Design Course Scale Pounds / in. Distribution of Nodal Forces Normal to the Contact Boundaries for Different Key Designs Standar d Key 0.2h 0.1h 483 Deep Key 0.2h 651 Large Key 0.4h 0.1h

Rigid Pavement Design Course Round Key 0.2h 0.1h h 0.1h Round Smooth Key h 1409 Scale Pounds / in

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

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

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