Meaning
Structural load-sharing mechanisms distribute the vertical forces applied by moving vehicles across the joints of adjacent concrete pavement slabs. Establishing effective joint shear transfer prevents differential deflection, which is the main cause of slab corner cracking and subgrade erosion under repeated traffic. This transfer is typically achieved through steel dowel bars, keyways, or aggregate interlock.
Mechanical Function
When a heavy vehicle wheel moves across a joint, the load is partially transferred from the loaded slab to the unloaded slab. This interaction reduces the maximum bending stress in both concrete elements. The presence of steel dowels ensures that the slabs deflect together, which maintains a flat riding surface.
Proper shear transfer is essential to prevent localized damage from heavy warehouse equipment.
Failure Mode
Repeated dynamic loads wear away the concrete around the dowels, leading to a loss of shear transfer efficiency. This degradation causes the joints to fault, creating a stepped surface that damages forklift tires and disrupts warehouse operations. It also accelerates subgrade erosion due to the increased movement of water and soil.
Design Method
Engineers specify the spacing and diameter of steel dowels based on the expected axle loads and concrete thickness. This calculation ensures the joint remains stable over the design life of the floor. Proper installation is required to prevent joint locking.
