“Load transfer” is a term used to describe the transfer (or distribution) load across discontinuities such as joints or cracks (AASHTO, 1993). When a wheel load is applied at a joint or crack, both the loaded slab and adjacent unloaded slab deflect. The amount the unloaded slab deflects is directly related to joint performance. If a joint is performing perfectly, both the loaded and unloaded slabs deflect equally. Load transfer efficiency is defined by the following equation:
This efficiency depends on several factors, including temperature (which affects joint opening), joint spacing, number and magnitude of load applications, foundation support, aggregate particle angularity, and the presence of mechanical load transfer devices. Figure 1 illustrates the extremes in load transfer efficiency. Most performance problems with concrete pavement are a result of poorly performing joints (ACPA, 2001). Poor load transfer creates high slab stresses, which contribute heavily to distresses such as faulting, pumping and corner breaks. Thus, adequate load transfer is vital to rigid pavement performance.
Load transfer across transverse joints/cracks is generally accomplished using one of the following:
- AASHTO Guide for Design of Pavement Structures. American Association of State Highway and Transportation Officials. Washington, D.C.↵
- Concrete Types. Web page on the American Concrete Pavement Association’s web site. http://www.pavement.com/PavTech/Tech/Fundamentals/fundtypes.html. Accessed 18 January 2002.↵