Characterizing the Load Spectra on a Rural Expressway in Binzhou, China: A Case Study

Abstract

Recently, China has experienced an increase in gross vehicle weights (GVW) due to rapid economic growth. Coupled with plans for extensive infrastructure expansion, the use of mechanistic-empirical (M-E) pavement design is necessitated. To meet these demands, it is essential to first characterize these extreme loads in the context of an M-E pavement design framework through load spectra. This case study documented the challenges in characterizing the unique axle configurations, heavy axle loads and traffic flow of Chinese vehicles for use in the M-E Pavement Design Guide (MEPDG). Traffic data were compiled from a weigh-in-motion (WIM) site on the Tianjing-Shantou Expressway, a connector between Beijing and Shanghai, near Binzhou (Shandong Province) from 2006-2007. This expressway experiences extremely heavy axle loads thought to be representative of typical expressway traffic. For example, a 90th percentile single axle load was 12.9 tons, nearly 1.75 times heavier than that on a rural representative interstate in the U.S. Although load limits are in place, it was found that they were frequently exceeded, with 31% of single axles and 56% of tandem axles exceeding the limits. The axle spacings and frequency of axle types observed from the WIM data varied significantly from axle configurations in the U.S., making it impossible to utilize the vehicle classes in the MEPDG. Additionally, the MEPDG requires only a single value to be entered for speed; however, large fluctuations in vehicle speed were observed among the Chinese vehicles. Using the MEPDG to assess the implications on required pavement thickness to mitigate pavement distress, it was found that the 10th percentile speed required an additional 28 cm of asphalt concrete over the thickness required for the average vehicle speed.