Impact of Trunnion Axle Groups on the Performance of Highway Infrastructure

The trunnion axle configuration has gained favor with many carriers of oversized and overweight loads. In addition, the frequency of interstate hauling of these specialized loads is increasing. The trunnion axle configuration allows for placement of more wheels in the transverse direction than conventional axle configurations, which may be more or less favorable to preventing premature load induced damage on highway pavements and structures. Currently the load allowances on multiple axle groups are non-uniform; the non-uniform allowances are disruptive to interstate commerce. In order to determine whether comparable overload limits can be endorsed for routine permitting of these two axle configurations in Texas, and to work towards uniformity of permitting practices in neighboring states, it is essential that state agencies understand the relative impact of trunnion axle loading on the premature damage of pavements. A project sponsored by the Texas Department of Transportation was therefore carried out at the University of Texas at Austin to determine the impact of trunnion axle loadings on the premature damage of both flexible and rigid pavements, relative to a standard tridem axle configuration. The research found that for flexible pavements, tridem axles are more damaging than trunnion axles; and for rigid pavements, trunnion axles are more damaging than tridem axles. For highway bridge structures, the damage caused by a truck with a trunnion axle does not significantly differ from that of a truck with a tandem axle.