Pavement Engineering M. Kharabsheh

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Continuously Reinforced Concrete Pavement

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Factors that must be Considered by Pavement Engineer. Must Know

Short Slabs can be designed and load transfer is provided by Aggregate Interlock (Contraction Joint)

The crack or contraction joint can be tied with Tie Bars of distributed steel to prevent the crack or joint from opening

Movement at joints can be permitted (Expansion Joints) and Dowel Bars are placed at the Joints to provide load transfer.

Pavement Engineering M. Kharabsheh

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Construction Joints with Tie Bars

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Contraction joint showing saw cut depth

Pavement Engineering M. Kharabsheh

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Aggregate Interlock (Contraction Joint)

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(Contraction Joint)

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(Contraction Joint)

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(Expasion Joint)

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Dowel Bars Storage

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Dowel Bars Construction

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Dowel Group Action

When traffic loads are applied at a joint, a portion of this load is transferred through the dowel bar into the next slab (this portion should be 50% for perfect load transfer)

The dowel bar immediately under the applied load bears a major portion of the load with other dowels assuming progressively lesser amount.

Pavement Engineering M. Kharabsheh

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Dowel Group Action

Maximum negative moment occurs at a distance 1.8L from the load.

The dowel bar immediately under the applied load carries full capacity (one full unit) and the portion of each dowel decrease to reach zero at a distance of 1.8L.

The corner dowel is the critical one for the edge load.

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Example

Load is 9000lb on each wheel

Assume 50% load transfer

Thickness= 10’ and Subgrade reaction = 50pci

Radius of relative Stiffness l = 51.1’ (from table 3.1 page 84)

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Example

X1 = 1 1/92 = x2/(92-12) x2 = 0.87 Effective Dowels group for load at A = xi =

1+.87+.74+.61+.48+.35+.22+.08 = 4.35 Total load carried by dowel

At point A = load from wheel

At A plus load from wheel at

Point B

Total load at A = 4500/(4.35*1)

+ 4500/(7.32*0.22) = 1035+135= 1170 lb

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Example on Bearing Stress by Dowel on Concrete

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