2013 Session: 219

• Effect of Controlling Heavy Vehicle Gaps on Long-Span Bridge Loading
  Abstract: Long-span road bridges are governed by congested traffic rather than free-flowing conditions. During congestion, heavy vehicles can get quite close to each other, thus giving potential critical loading events for the bridge. In this paper, the effects of a system capable of warning truck drivers when the gap falls below a certain threshold are investigated. The effects are studied both in terms of increase in traffic disruption and reduction in loading. Ideally, the minimum distance between trucks should be adjusted for the site-specific traffic features and for the load the bridge is able to carry safely. Doing so, it will be possible to allow for future increase in truck weight regulations and/or heavy traffic volumes, by adjusting the control gap value. Importantly, the proposed system does not presume any restriction to the truck weight. By contrast, the system is meant to be an alternative way of limiting the load on long-span bridges by keeping the trucks apart, rather than by limiting the truck weight. The introduction of such a gap control system is studied by means of micro-simulation. The car-following model used here has been shown able to replicate many observed congestion patterns. Results show that the introduction of the gap control system does not significantly disrupt the traffic further. On the other hand, having only 10% of trucks complying with the gap control device beneficially reduces the total traffic loading by about 10%. When most trucks are compliant, nearly 50% reduction in the total load can be attained.
  Authors: Caprani, Colin C.; OBrien, Eugene John; Lipari, Alessandro
  Authors: Caprani, Colin C.; OBrien, Eugene John; Lipari, Alessandro
  Year: 2013
  Document Type: Paper
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-1045
• Dynamic Load-Sharing of Longitudinal-Connected Air Suspensions of Triaxle Semitrailer
  Abstract: The effects of suspension parameters and driving conditions on dynamic load-sharing of longitudinal-connected air suspensions of a tri-axle semi-trailer are investigated in this study. A novel nonlinear model of a multi-axle semi-trailer with longitudinal-connected air suspensions is formulated based on fluid mechanics and thermodynamics and validated through test results. The effects of road surface conditions, driving speeds, air line inside diameter and connector inside diameter on dynamic load-sharing capability of the semi-trailer were analyzed in terms of load-sharing criteria. Simulation results indicate that, when larger air lines and connectors are employed, the DLSC (Dynamic Load-Sharing Coefficient) optimization ratio reaches its peak value when the road roughness is medium. The optimization ratio fluctuates in a complex manner as driving speed increases. The results also indicate that if the air line inside diameter is always assumed to be larger than the connector inside diameter, the influence of air line inside diameter on load-sharing is more significant than that of the connector inside diameter. The proposed approach can be used for further study of the influence of additional factors (such as vehicle load, static absolute air pressure and static height of air spring) on load-sharing and the control methods for multi-axle air suspensions with longitudinal air line.
  Authors: Chen, Yikai; He, Jie; King, Mark J.; Liu, Hongchao; Zhang, Weihua
  Authors: Chen, Yikai; He, Jie; King, Mark J.; Liu, Hongchao; Zhang, Weihua
  Year: 2013
  Document Type: Paper
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-1117
• Methodology to Estimate Added Bridge Costs due to Overweight Trucks
  Abstract: Overweight vehicle operations impact bridge infrastructure by increasing the frequency of maintenance, rehabilitation and reconstruction/replacements activities. This creates an added cost to the highway agency. The methodology to estimate the added cost requires the AASHTO design vehicles for bridges to be correlated to the observed vehicles on the road. This paper presents a statistical approach to accomplish this task and it is illustrated by using the state highway network in Indiana. Since bridge damage cost is not only a factor of gross vehicle weight but a function of all the three overweight vehicle variables: gross vehicle weight, axle spacing and axle loads, adopting a permit structure on the basis of gross vehicle weight only will result in some vehicles underpaying by about 92%.
  Authors: Agbelie, Bismark Richard Delaidem Kofi; Labi, Samuel; Sinha, Kumares C.
  Authors: Agbelie, Bismark Richard Delaidem Kofi; Labi, Samuel; Sinha, Kumares C.
  Year: 2013
  Document Type: Paper
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-4198
• International Bridge Formulas and Resulting Bridge Load Stresses for Truck Weight Regulation
  Abstract: This paper identifies and characterizes existing international bridge formulae and presents the results of an analysis of bridge load stress effects resulting from these formulae. This is done to provide insight into this method of regulating truck size and weight for future decisions regarding the creation of new bridge formulae, or modification of existing ones.The bridge formulae vary significantly in terms of the level of restrictiveness of allowable loads and imposed load effects due to both the formulae themselves and truck configurations. Bridge formulae should be designed to limit the imposed stresses on bridges based on criteria suitable to a jurisdiction’s truck fleet and infrastructure characteristics in order to adequately regulate truck sizes and weights. They should also be applied to all consecutive axle group combinations to ensure adequate internal axle load distribution.Many issues may result from the implementation of an unsuitable bridge formula for the infrastructure and transportation characteristics of a jurisdiction in terms of the design overstress criteria and additional axle spacing and weight limits. The unintended, and possibly undesirable, outcomes of implementation of a bridge formula must be monitored and resolved for safety, dynamic performance and infrastructure impacts. With the continuously changing infrastructure and truck transportation characteristics, bridge formulae must be re-evaluated and updated to ensure the adequacy to limit weights.
  Authors: Moshiri, Maryam; Montufar, Jeannette
  Authors: Moshiri, Maryam; Montufar, Jeannette
  Year: 2013
  Document Type: Paper
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-4286
• Effect of Controlling Heavy Vehicle Gaps on Long-Span Bridge Loading
  Authors: Lipari, Alessandro
  Authors: Lipari, Alessandro
  Year: 2013
  Document Type: Presentation
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-1045
• Dynamic Load-Sharing of Longitudinal-Connected Air Suspensions of Triaxle Semitrailer
  Authors: Chen, Yikai
  Authors: Chen, Yikai
  Year: 2013
  Document Type: Presentation
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-1117
• International Bridge Formulas and Resulting Bridge Load Stresses for Truck Weight Regulation
  Authors: Montufar, Jeannette
  Authors: Montufar, Jeannette
  Year: 2013
  Document Type: Presentation
  Subject: Freight Transportation
  Session: 219
  Paper Number: 13-4286