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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
A B
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 ThreadedZJoint
Not Recommended
Tied Joints
•# 4 or #5 bars;
•24” to 48” long
•18” - 48” spacing
Rigid Pavement Design Course
0% Load Transfer
60.02δδloadedtot
0δunloaded
unloaded
δloaded
δ
tot
δ
Deflection of Loaded Slab
Deflection of unloaded Slab
Total Deflection
Where:
Applied Wheel Load (P)
0.026"Loaded δ 0 Unloadedδ
Rigid Pavement Design Course
Applied Wheel Load (P)
100% Load Transfer
30.01δ2
1δδ
totunloadedloaded
loadedunloadedtotδδδ
100%100δ
δLT
L
unlδ
0.013"Loaded δ 0.013" Unloadedδ
Rigid Pavement Design Course
Load Transfer
U 100L
LTE x
σ
Total U L fe L LLTE
LTE LTE
LTEσ
LTEδ
LTEδ
0
1.0(.55,100% LTE)
(.67,44% LTE)(1.0,0% LTE)
100u
L
LTE x
Total U L
1fe
L LTE
/
/
e w LTE
e w o LTE
Rigid Pavement Design Course
DowelBar
Subgrade
Critical Stress forMid Slab Loading
SlabThickness
Slab Length (L)
Single Axle Loading
Agg
Subbase
he
w
s
a
Traffi
c Lan
e
Should
erH
inge
Join
t
Hin
ge Jo
int
Do
3
4 2
Eh=
12 1- k
Tied Shoulder Effect
Rigid Pavement Design Course
7mm Wide
Lubricated, smooth dowel bar
d/2
(a)
(b)
d/4 except forearly entry sawcut(25 mm min.)
Load Transfer – Crack Width Requirements
Rigid Pavement Design Course
Load Transfer – Crack Width Factors
Rigid Pavement Design Course
101520253035404550
6 7 8 9 10 11 12 13 14 15 16
Slab Thickness (in)
Cra
ck W
idth
(m
ils)
Load Transfer – Crack Width Requirements:Thickness Factors
Rigid Pavement Design Course
Emergency Joints?
Rigid Pavement Design Course
Eff
ect
ive
ne
ss
, pe
rce
nt
Loading Cycles, 100 000
Influence of Joint Opening on Effectiveness, 9 Inch Concrete Slab, 6 Inch Gravel Subbase (82)
0 1 2 3 4 5 6 7 8 9 100
40
60
80
100
200.085
0.065
0.045
0.035
Joint Opening 0.025 in.
Rigid Pavement Design Course
Eff
ect
ive
ne
ss
, pe
rce
nt
Loading Cycles, 100 000
0 1 2 3 4 5 6 7 8 9 100
20
40
60
80
100
Influence of Joint Opening on Effectiveness, 7 Inch Concrete Slab, 6 Inch Gravel Subbase (82)
0.065 0.045
0.035
0.025
Joint Opening 0.015 in.
Rigid Pavement Design Course
Influence of joint opening on effectiveness (9 in. slab, cement stabilized subbase, k=542 pci)
Loading Cycles, 100 000
Eff
ect
ive
ne
ss
, pe
rce
nt
0 1 2 3 4 5 6 7 8 9 100
20
40
60
80
100
9-in. Slab
0.065-in.
0.065-in.
0.035-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 CourseEffect of Slab Thickness on Maximum Shear Stresses at
Joint Interface
Ma
x. S
he
ar S
tre
ss
at
Join
t In
terf
ac
e, p
si
60
50
40
30
20
10
010 12 14 16 18 20 24
Agg 107
Agg=106
Agg=105
Agg=5x104
Agg=104
Agg=5x103
Agg=103
Agg=102
Rigid Pavement Design Course
Jo
int
Eff
. %
10,000
Subgrade Mod. X Mod. Of Relative Stiff., psi-1
Figure 4-18. Relation between Joint Efficiency (Eff) and
Spring Stiffness (Agg)
0.2 0.6 1.0 1.4 1.8 2.2 2.6 3.0 3.4
100
80
60
40
20
0
Agg=106psi
Agg=105psi
Agg=5x104psi
Agg=104 psi
Agg=5x103psi
Agg=103psi
Agg=102psi
Rigid Pavement Design Course
Modulus of Aggregate Stiffness, in.
Effect of Aggregate Interlock in Reducing Maximum Tensile Edge Stresses
Max
. T
ensi
le E
dg
e S
tres
s x
(Sla
b T
hic
knes
s)2 ,
k-in
.in
.
Free E
dge
Interior
Edge W/Agg
Agg 106
30 60 100
144
120
96
72
48
24
0
Agg=105
30 60 100
144
120
96
72
48
24
0
Rigid Pavement Design Course
30 60 100
144
120
96
72
48
24
0
Agg=104
30 60 100
144
120
96
72
48
24
0
Modulus of Aggregate Stiffness, in.
Max
. T
ensi
le E
dg
e S
tres
s x
(Sla
b T
hic
knes
s)2 ,
k-in
.in
.
Agg102
Rigid Pavement Design Course
Effect of Aggregate Interlock in Reducing Maximum Edge Deflection
Load
Subgrade Mod. x (Mod. Of Relative Stiff.)2, in.
Ma
x. E
dg
e D
efl
ect
ion
, in
.
0 0.08 0.16 0.24 0.32
0.12
0.10
0.08
0.06
0.04
0.02
00 0.08 0.16 0.24 0.32
0.12
0.10
0.08
0.06
0.04
0.02
0
Free
Edg
eInterio
rEdge W
/Agg
Agg 106Agg=105
Rigid Pavement Design Course
0 0.08 0.16 0.24 0.32
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
00 0.08 0.16 0.24 0.32
Agg=104 Agg102
Ma
x. E
dg
e D
efl
ect
ion
, 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" 45"
Rigid Pavement Design CourseTensile Stress Contours for a Standard Key on a 10 in. Cement
Stabilized Base
P=200 psi
12" 12"
Esub = 10,000 psi
200 150 100 50
0
50
100
150
200
0 0
0
200
150
100
50
400350300
300
200
100 0
Rigid Pavement Design Course
Scale
Pounds / in.
Distribution of Nodal Forces Normal to the Contact Boundaries for Different Key Designs
Standard
Key
0.2h
0.1h
483
Deep Key
0.2h
0.2h 651
Large Key
0.4h
0.1h
822
0 100 200 300
Rigid Pavement Design Course
Round Key
0.2h
0.1h
859
0.2h
0.1h
Round Smooth Key
h
1409
Scale
Pounds / in.
0 100 200 300
Rigid Pavement Design Course
Effect of Key Design on Maximum Tensile Stress in the Slab*
Key Design KeywayPsi (MPa)
Key Psi (MPa)
Standard Key 312 (2.15) 586 (4.04)Large Key 1023 (7.05) 1229 (8.47)Deep Key 259 (1.78) 589 (4.06)
Round Key 451 (3.11) 501 (3.45)Round Smooth
Key201 (344) 344 (2.37)
Z-Key 721 (4.97) 274 (1.89)
* Slab thickness was 16 in. (40.6 cm)
Rigid Pavement Design Course
(a) Doweled Joint
Figure 4-37. Possible Joint Designs for the Example Problem
(b) Tied Joint with Aggregate Interlock
(c) Joint With Aggregate Interlock On Stab. Base
12"
12" 12"
4"
Rigid Pavement Design Course
(e) Thickened Edge Joint (f) Butt Joint
(d) Butt Joint on Stab. Base
Figure 4-37. Continued
12"
6"
12" 16"