Joint Types and Behavior. Rigid Pavement Design Course Jointing Patterns

Joint Types

and Behavior

Rigid Pavement Design Course

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

• Subbase/Slab interface friction

• Load transfer

• 1) Shear – aggregate interlock

2) Dowel


A B

Contraction Joints• Control trans. Cracking

• Formed by weakened joint

- Saw Cutting

- Grooving

- Insert Strip

- With and without dowel


Construction Joints• Planned interruptions

• Isolation joint

• Transverse or Longitudinal

ED


Isolation Joint• Space for expansion

- temp/moisture increase

- Use compressible filler, LT or slab thickening

C


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


Longitudinal Joints

Tie Bar

Tie Bolt

Dowel Bar

F

H

G


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


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


Applied Wheel Load (P)

100% Load Transfer

30.01δ2

1δδ

totunloadedloaded

loadedunloadedtotδδδ

100%100δ

δLT

L

unlδ

0.013"Loaded δ 0.013" Unloadedδ


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


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


7mm Wide

Lubricated, smooth dowel bar

d/2

(a)

(b)

d/4 except forearly entry sawcut(25 mm min.)

Load Transfer – Crack Width Requirements


Load Transfer – Crack Width Factors


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


Emergency Joints?


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.


Eff

ect

ive

ne

ss

, pe

rce

nt


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.


Influence of joint opening on effectiveness (9 in. slab, cement stabilized subbase, k=542 pci)


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


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


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


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


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


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


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


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


Round Key

0.2h

0.1h

859

0.2h

0.1h

Round Smooth Key

h

1409

Scale

Pounds / in.

0 100 200 300


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)


(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"


(e) Thickened Edge Joint (f) Butt Joint

(d) Butt Joint on Stab. Base

Figure 4-37. Continued

12"

6"

12" 16"

Documents

Joint Types and Behavior. Rigid Pavement Design Course Jointing Patterns