Longitudinal joints in concrete pavements, incorporating tie bars at their mid-depth, are not designed for lateral movement. Their primary purpose is to address the potential for differential settlement in the pavement foundation and warping caused by moisture and temperature fluctuations.
Regularly spaced longitudinal joints, typically at intervals like 4.5 meters, act as pre-determined breaking points. When uneven settlement occurs, the tie bars function as hinges, enabling the concrete carriageway to accommodate the settlement without uncontrolled cracking. This design feature, as highlighted by the Ministry of Transport (1955), prevents structural damage and maintains the pavement’s functionality.
Moreover, these joints also mitigate the effects of warping, a phenomenon where concrete slabs distort due to moisture and temperature gradients. By permitting a slight angular movement at the joints, stresses that could otherwise lead to cracking are relieved.
The inclusion of dowel bars in longitudinal joints serves two essential functions:
- Load Transfer: In the event of uneven settlement between adjacent panels, dowel bars facilitate load transfer, helping to maintain a level and smooth riding surface. This is crucial for ensuring the pavement’s usability and safety.
- Joint Closure: Dowel bars help keep the longitudinal joints tightly closed, preventing debris from entering and minimizing the potential for water infiltration. This, in turn, protects the underlying layers of the pavement and extends its lifespan.
In summary, longitudinal joints in concrete pavements, although not designed for lateral movement, play a crucial role in accommodating differential settlement, mitigating warping effects, and ensuring the structural integrity of the pavement. The strategic placement of tie bars and dowel bars within these joints contributes to their overall functionality and the longevity of the pavement.