A Novel Sensor System for Measuring Wheel Loads of Vehicles on Highways
With the development of the highway transportation and business trade, vehicle Weigh-In-Motion (WIM) technology has become a key technology for measuring traffic loads. In this paper a novel WIM system based on monitoring of pavement strain responses in rigid pavement was investigated. In this WIM system multiple low cost, light weight, small volume and high accuracy embedded concrete strain sensors were used as WIM sensors to measure rigid pavement strain responses. In order to verify the feasibility of the method, a system prototype based on multiple sensors was designed and deployed on a relatively busy freeway. Field calibration and tests were performed with known two-axle truck wheel loads and the measurement errors were calculated based on the static weights measured with a static weighbridge. This enables the weights of other vehicles to be calculated from the calibration constant. Calibration and test results for individual sensors or three-sensor fusions are both provided. Repeatability, sources of error, and weight accuracy are discussed. Successful results showed that the proposed method was feasible and proven to have a high accuracy. Furthermore, a sample mean approach using multiple fused individual sensors could provide better performance compared to individual sensors.
A Review and Perspective about Pavement Monitoring
Pavement monitoring is an essential part of pavement research and very important to the socialized transportation system. Since the middle of 20th century, various sensing technologies have been devoted to improve sensitivity, functionality, scale, survival rate and resistance to harsh environment. At the same time, other related monitoring system, such as bridge monitoring, Weigh-in-Motion (WIM), traffic classification systems are also developed vigorously, and can be integrated with pavement monitoring with more benefit.In this paper, pavement monitoring is categorized based on the monitoring frequencies and sensing technologies, and each category is traced back with important development described. The history and current status of the related and integrated monitoring systems are reviewed according to different monitoring targets and sensing methodologies. Some new developments representing future trends are also discussed.
MOVING LOADS ON A PLATE ON ELASTIC FOUNDATION
A number of studies have been conducted recently to find the dynamic response of multilayered media as models of pavement systems to moving loads. The dynamic response of an infinite plate on an elastic foundation subjected to constant amplitude or harmonic moving loads was investigated. The advance velocity was assumed to be constant. Formulations were developed in the transformed field domain using a double Fourier transform in space and moving space for moving constant loads; a triple Fourier transform in time, space, and moving space to include the initial application of the load for moving harmonic loads; and a double Fourier transform in space and moving space for the steady-state response to moving harmonic loads. The effects of velocity, load frequency, and damping on the deflected shape, and the maximum displacement were investigated. The critical (resonant) velocities and frequencies were obtained by analyses, and expressions to find them were suggested. The effect of multiple loads on the maximum displacement was also investigated. The variation of the maximum dynamic displacement was affected by the distances and the differences in phase between the loads.