Analysis Procedure for Load-Zoning Pavements

Abstract

Most load-zoned roads in Texas are still posted with a gross vehicle weight limit of about 260 kN, corresponding to the legal load limit at the time these roads were designed and built. Since the load from a vehicle is transmitted to the pavement through its axles, establishing load limits based on axle load and axle configuration is a more rational approach than the one currently used. In recognition of the need for a better methodology of load-zoning pavements, the Texas Department of Transportation funded a project to develop a procedure for evaluating load restrictions on the basis of axle load and axle configuration. Research efforts conducted at the Texas Transportation Institute led to the development of the Program for Load-Zoning Analysis (PLZA), which pavement engineers may use to evaluate the need for load restrictions and to determine, as appropriate, the single- and tandem-axle load limits based on a user-prescribed reliability level. To predict the induced pavement response under surface wheel loads, PLZA uses a layered elastic pavement model that permits users to characterize pavement materials as linear or nonlinear. The predicted horizontal strain at the bottom of the asphalt layer and the vertical strain at the top of the subgrade are used to evaluate pavement performance. To combine the effects of different axle loads and axle configurations, PLZA uses Miner’s hypothesis of cumulative damage to predict service life and the probability of pavement failure within a prescribed analysis period. The methodology for load-zoning is described, and its application using data collected on in-service pavements is demonstrated.