Superload Effect on Pavement Life

Tuesday, April 26, 2022 - 15:30

Superloads (SLs) are a class of vehicles that typically exceed both gross vehicle weight limits and axle load limits, in addition to occupying two or more lanes of traffic. In PA, SLs require special permits but their effect on pavement distresses have not been evaluated. In this study, lab and computational analyses were combined to quantify the effect of SLs on flexible and rigid pavements. In rigid pavements, SLs were found to disproportionately increase fatigue damage particularly under conditions of high positive temperature gradients. Laboratory testing also indicated that this damage increases non-linearly, so that it is higher for pavements that are already significantly damaged than those that are still relatively undamaged. Additionally, the heavy loads increased the dowel looseness developed at transverse joints, although this increase would require 1,000 of passes of a SL. A higher dowel looseness may potentially lead to higher faulting. Computational analysis found that this potential was enhanced when the slab experienced high temperature gradients, as would be the case in late spring and summer. Untied shoulders and poor aggregate interlock are also other factors that may cause an increase in looseness and hence faulting. For flexible pavements, the fatigue damage, rutting, and potential for shear failure were particularly high when the AC and base layers were thin and relatively less stiff. However, as in the rigid pavements case, a single pass of a SL truck does not cause any appreciable damage to the flexible pavement. Predictive models for damage caused to flexible and rigid pavements were developed and implemented into Excel workbooks. The full documents are available online at the Pennsylvania Department of Transportation web site at


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