Joint Design - PowerPoint PPT Presentation

1 / 34
About This Presentation
Title:

Joint Design

Description:

Define tie bar requirements for longitudinal joints. Types of Joints. Contraction joint ... Rubberized asphalt (ASTM D3405) Silicone. Preformed compression seals ... – PowerPoint PPT presentation

Number of Views:130
Avg rating:3.0/5.0
Slides: 35
Provided by: kurts3
Category:
Tags: astm | design | joint

less

Transcript and Presenter's Notes

Title: Joint Design


1
SESSION 7
  • Joint Design

2
Objectives
  • Identify types of joints
  • Determine suitable joint spacings
  • Determine load transfer requirements
  • Develop joint reservoir designs
  • Define tie bar requirements for longitudinal
    joints

3
Types of Joints
  • Contraction joint
  • Construction joint
  • Expansion joint

4
Joint Type?
Butt Joint
Construction Joint (transverse or longitudinal)
5
Joint Type?
Initial Sawcut
Contraction Joint (transverse or longitudinal)
6
Joint Type?
Expansion Joint with Filler Material
Expansion Joint
7
Elements of Joint Design
  • Transverse joints
  • Joint spacing
  • Load transfer design
  • Sealant reservoir design
  • Longitudinal joints
  • Tie bar design

8
JPCP Joint Spacing
  • Short enough to prevent mid-slab cracking
  • Intricately linked with
  • Slab thickness
  • Base support
  • Climatic conditions
  • Generally between 3.6 and 6.1 m (12 and 20 ft)

9
Example JointSpacing Guidelines
10
Uniformity of Joint Spacing
  • Uniform joint spacing
  • Joints spaced at fixed intervals
  • Variable joint spacing
  • 3 or 4 joint spacings in a repeating pattern,
    e.g., 3.7 - 4.6 - 4.0 - 4.3 m (12 -15 - 13 - 14
    ft)
  • Intended to reduce rhythmic response of vehicles

11
Joint Orientation
  • Perpendicular
  • Joints perpendicular to centerline
  • Skewed
  • Joints placed at an angle to pavement centerline
    (counterclockwise skew)
  • May be beneficial for nondoweled joints
  • Limit skew to minimize corner breaks (maximum
    110)

12
Example Variable Spacing and Skewed Joints
  • 4.6 m

4.3 m
4.0 m
3.6 m
(12 ft)
(15 ft)
(13 ft)
(14 ft)
13
Skewed Joints
14
LoadTransfer
  • Ability of joint to convey wheel load from one
    side to the next
  • Reduces deflections
  • Reduces pumping, faulting
  • Methods
  • Dowels
  • Aggregate interlock

15
Load TransferIllustration
0 Load Transfer
  • Wheel
  • Load

Direction of Traffic
Leave Slab
Approach Slab
16
Load TransferRecommendations
  • Dowels recommended for most highway pavements
    (slab thickness gt 200 mm 8 in)
  • Minimum 32 mm diameter (38 mm preferred)
  • Corrosion inhibitor required

17
Dowel Layout
Conventional Spacing
18
Alternative Dowel Layout
Cluster Spacing
19
Joint Sealing and Reservoir Design
  • Purposes of joint sealing
  • Reduce moisture infiltration
  • Keep out incompressibles
  • Cost-effectiveness of sealing?

20
Consideration Factors
  • New or rehabilitation design
  • Climate
  • Joint design
  • Base and subgrade type and drainability
  • Local experience
  • Others?

21
Joint Channel Design
  • Unsealed joints
  • Crack control sawcut (3 mm 1/8 in

22
Joint Channel Design (continued)
  • Sealed joints
  • Crack control sawcut (3 mm 1/8 in)
  • Joint reservoir sawcut (typ. 10 to 15 mm 0.4 to
    0.6 in wide)

23
Joint Reservoir Sawcut
Reservoir Widening Cut
Depth of Widening Cut (25 to 38 mm) (1 to 1.5 in)
Crack Control Sawcut
24
Joint Reservoir Design
  • Selection of sealant material
  • Estimation of joint movements
  • Determination of required joint width

25
Sealant Materials
  • Rubberized asphalt (ASTM D3405)
  • Silicone
  • Preformed compression seals
  • Placed in state of compression
  • Must be compressed 20 to 50 of normal width over
    service life

26
Joint Reservoir
Width
  • 3 to 6 mm
  • (1/8 to 1/4 in) Recess

Depth
Backer Rod
Joint Sealant
Shape Factor W / D
27
Example Compression Seal Installation
Compressed Width
Reservoir Depth
Preformed Compression Seal
28
Estimating Joint Movements
  • ?L C L (? ?T ?)
  • ?L Joint opening, in
  • C Adj. factor (0.8 gran. base, 0.65 stab.)
  • L Joint spacing, in
  • ? Thermal coef. of expansion (3.8 to
  • 6.6 x 10-6), in/in/oF
  • ?T Temperature range, oF
  • ? Drying shrinkage coefficient (2 to
  • 8 x 10-4), in/in

29
Required Joint Reservoir
  • Hot-poured/silicone sealants
  • Required joint width
  • W ?L / S
  • W Required joint width
  • ?L Joint opening
  • S Allowable sealant strain
  • Required sealant depth
  • Apply proper shape factors

30
Required Joint Reservoir (continued)
  • Compression seals
  • Select uncompressed seal width
  • USW gt ?L / (Cmax - Cmin)
  • Cmax 0.5 (typ) Cmin 0.2 (typ)
  • Determine width of sawcut
  • W (1 - Pc) USW
  • Pc of compression at installation

31
Longitudinal Joint Design
  • Contraction (sawed) joints
  • Between lanes or between lane - shoulder
  • Adequate sawing depth/timing
  • Effective tie bar system
  • Construction (butt) joint
  • Commonly between lane and shoulder
  • Effective tie bar system

32
Longitudinal Contraction Joint
33
Longitudinal Construction Joint
34
Summary
  • Joint types
  • Joint spacing guidelines
  • Load transfer recommendations
  • Joint sealant system
  • Longitudinal joint requirements
Write a Comment
User Comments (0)
About PowerShow.com