1. Dowel bars and tie bars are used in concrete pavement design. Dowel bars are placed across transverse joints and transfer loads between slabs while allowing for joint openings. Tie bars are placed longitudinally and prevent transverse cracking and lane separation. 2. The design of dowel bars involves determining the length using an equation considering bar diameter and joint width, and checking that the load transfer capacity meets requirements. Tie bar design involves determining the length based on bar diameter and bond strength, and the spacing is calculated based on the required bar area.

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Dowel Bars, Tie Bars
and Their Design
P a v e m e n t D e s i g n
Bhavya S. Jaiswal
Btech civil, Mtech Transportation
Engineering

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Dowel bars and its design
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• Placed across the transverse joints at
mid depth of the slab
• Reduces faulting and also prevents
corner cracking
• Transfers load from one to another slab
but not prevent the joints from opening.
• They are generally round, smooth,
epoxy coated bars.
Prepared by: Bhavya S. Jaiswal

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Design of the dowel bars
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1. Apply the following equation to find length of the dowel bars , Ld
𝐿𝑑 = 5𝑑
𝐹𝑓(𝐿𝑑 + 1.5𝛿)
𝐹𝑏(𝐿𝐷 + 8.8𝛿)
Where,
Ld = length of the bar
d = diameter of the bar
𝛿 = joint width
Ff = permissible stress in bending
Fb = permissible stress in bearing
2. Make a relation with the above equation and put trial value of Ld as 45cm and find
the Ld
Length of the Dowel bar = Ld + 𝛿 and provide a round about length as LDprovided
Prepared by: Bhavya S. Jaiswal

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Design of the dowel bars
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3. Find the load transfer capacity by the equations…
𝑃𝑆 = 0.785 × 𝑑2 × 𝐹𝑠
𝑃𝑓 =
2 × 𝑑3 × 𝐹𝑓
𝐿𝑑 + 8.8𝛿
𝑃𝑏 =
𝐹𝑏 × 𝐿𝑑
2
× 𝑑
12.5(𝐿𝑑 + 1.5𝛿)
Fs = permissible
stress in Shear
Prepared by: Bhavya S. Jaiswal

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Design of the dowel bars
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4. Take load transfer capacity as 40% if not given and find
0.4𝑃
𝑃𝑠
,
0.4𝑃
𝑃𝑓
,
0.4𝑃
𝑃𝑏
take which ever is maximum as a desire capacity and
P= design wheel load
5. Find the effective load transfer as 1.8𝑙
where, 𝑙 = radius of relative stiffness
Prepared by: Bhavya S. Jaiswal

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Design of the dowel bars
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Actual
capacity = [1 +
1.8𝑙 − 35
1.8𝑙
+
1.8𝑙 − 70
1.8𝑙
+
1.8𝑙 − 105
1.8𝑙
+
1.8𝑙 − 140
1.8𝑙
]
Assume 35cm spacing and find the actual capacity…
Check if Actual capacity > Required capacity
if it is not greater than reduce the spacing and check it again
Prepared by: Bhavya S. Jaiswal

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Tie bars and design of tie bar
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• Placed across longitudinal joints at
mid depth of the pavement.
• It reduces the transverse cracking.
• Prevents lane separation and also at
the same time prevents differential
deflection in the pavement.
• Generally, such bars are made up of
deformed epoxy coated steel.
Prepared by: Bhavya S. Jaiswal

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Design of the Tie bars
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1. Find the length of the tie bar using the following equation…
𝜎𝑠𝑡×∅
2×𝜏𝑏𝑑
Where,
𝜎𝑠𝑡 = working tensile stress (17.50)
∅ = diameter of the bar (max 20mm)
𝜏𝑏𝑑 = bond strength (24.6)
2. Find out the spacing between the bars…
1000
𝐴𝑠𝑡
× 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑠𝑖𝑛𝑔𝑙𝑒 𝑏𝑎𝑟
Prepared by: Bhavya S. Jaiswal

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Design of the Tie bars
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• Where ,
𝐴𝑠𝑡 =
𝐹×𝑤×𝐵×ℎ
𝜎𝑠𝑡
Where,
w = unit weight of the concrete (2400kg/𝑐𝑚2)
F = friction (1.5)
B = width of the slab (per lane)
h = thickness of the slab
𝜎𝑠𝑡 = 17.5kg/𝑐𝑚2
Prepared by: Bhavya S. Jaiswal

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References
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• IRC-58:2012
• The constructor : https://theconstructor.org/practical-guide/tie-bar-
constructions/37378/
• Engineerwing : https://www.engineerwing.com/2017/05/types-of-
concrete-pavement-uses.html
• Dowel bars : pavement interactive;
https://pavementinteractive.org/reference-desk/pavement-types-
and-history/pavement-types/dowel-bar/
Prepared by: Bhavya S. Jaiswal