Innovative Bridge Weigh-in-Motion System for Bridge Maintenance: A Case Study with Bridge on Highway I-59

One of the primary causes of bridge failure is overloaded commercial vehicles. In order to prevent deterioration of a bridge it becomes important not only to design and build bridges according to the regulations but also enforce commercial vehicle maximum weight standards. For these reasons, a bridge weigh-in-motion (B-WIM) system should be a key asset in maintaining the balance sought. The B-WIM device placed on the soffit of a bridge includes strain transducers and, usually, separate axle detectors placed on the deck, to determine axle loadings, axle spacing, speed, and gross vehicle weight as a truck moves across the bridge. B-WIM devices have become an important means to better enforcement and better bridge design in many international countries. The objective of this paper is to gather as much information as possible about existing and emerging B-WIM systems in order to determine its potential for implementation in the United States. The information sought includes the benefits of using B-WIM, the steps involved in implementing its technology in the United States, and how to evolve the current systems. The paper summarizes an assessment study that was carried out on an Interstate 59 (I-59) bridge structure in Alabama with a B-WIM (Bridge Weigh-In-Motion) system called SiWIM, developed in Slovenia by ZAG and CESTEL. The main objective of this study was to assess the performances of the system based on the preliminary data, and to acquire experience on its implementation, in order to elaborate technical rules for the choice of bridge types suitable for B-WIM, and how to design their instrumentation. The accuracy classes of the system with respect to the specifications are assessed. The data were analyzed with regard to overloading on axles (single axle or axle group) or gross weight overloading and to calculate what proportion of the loaded vehicles was overloaded, either on axles or relative to the vehicle’s gross weight. The effect on the road structure was also analyzed, because dimensioning for the road structure is based on knowledge of the traffic or on an ability to assess the volume of traffic accurately. Moreover, the damaging impact of an overloaded vehicle may vary, in that the number of standard axle loads per vehicle factor and the incidence of overloading are not covariants. Therefore, measurements were carried out to gain a picture of the make-up of the heavy traffic in terms of loads and the incidence of overloading. By gaining a picture of the make-up of the heavy traffic in terms of loads and the incidence of overloading it is possible to establish a foundation in fact for (a) appropriate actions to achieve better compliance with regulations, (b) planning of road maintenance, and (c) dimensioning the road structure in road building and road maintenance.