SlabCalc LogoSlabCalc Concrete Technical Division

Load Transfer

The mechanism by which loads on one slab panel are shared with adjacent panels across a joint

Load transfer is the mechanism by which loads applied to one slab panel are shared with adjacent panels across a joint. Effective load transfer prevents faulting—the condition where one side of a joint settles lower than the other—creating uneven surfaces and accelerated joint deterioration.

Why It Matters

Without load transfer, each slab panel acts independently. A vehicle crossing a joint loads one panel fully while the adjacent panel carries nothing. This causes differential deflection: the loaded panel deflects downward while the unloaded panel stays put. Over time, this repeated uneven loading erodes the subgrade beneath the joint, causing permanent faulting and progressive deterioration.

For residential driveways and garage floors, load transfer prevents the common problem of one slab section sitting higher than its neighbor at joints—a tripping hazard and water pooling point.

Technical Details

Load transfer mechanisms:

  • Aggregate interlock: Cracked concrete faces interlock at roughened surfaces. Works in control joints where cracks are tight (< 0.035 inches). Effectiveness decreases as crack width increases.
  • Dowel bars: Smooth steel bars placed across joints. Primary engineered load transfer device. Allows horizontal movement while transferring vertical loads. Standard for pavements and heavy-duty slabs.
  • Keyways: Formed or saw-cut tongue-and-groove profile at construction joints. Less effective than dowels but simpler. Common in residential construction.
  • Tie bars: Deformed bars across longitudinal joints preventing lane separation. Hold slabs together (unlike dowels which allow movement).

Load Transfer Efficiency (LTE):

  • Measured as deflection ratio between loaded and unloaded sides
  • 100% LTE: both sides deflect equally (perfect transfer)
  • 0% LTE: no transfer, loaded side deflects fully
  • Target: 75%+ for acceptable performance
  • Below 50%: joint rehabilitation needed

Factors affecting load transfer:

  • Joint opening width (wider = less interlock)
  • Aggregate size and angularity (larger, angular = better interlock)
  • Temperature (cold weather opens joints, reducing interlock)
  • Traffic volume and load magnitude
  • Subgrade support condition

Learn More

← Browse all glossary terms