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Driving vehicles with one or more passive trailers has difficulties in both forward and backward motion due to inter-unit collisions, jackknife, and lack of visibility. Consequently, advanced driver assistance systems (ADAS) for multi-trailer combinations can be beneficial to accident avoidance as well as to driver comfort. The ADAS proposed in this paper aims to prevent unsafe steering commands by means of a haptic handwheel. Furthermore, when driving in reverse, the steering-wheel and pedals can be used as if the vehicle was driven from the back of the last trailer with visual aid from a rear-view camera. This solution, which can be implemented in drive-by-wire vehicles with hitch angle sensors, profits from two methods previously developed by the authors: safe steering by applying a curvature limitation to the leading unit, and a virtual tractor concept for backward motion that includes the complex case of set-point propagation through on-axle hitches. The paper addresses system requirements and provides implementation details to tele-operate two different off- and on-axle combinations of a tracked mobile robot pulling and pushing two dissimilar trailers.

In bridges with light curvature, curvature effects may be ignored if they are within acceptable range. In contrast to ACI 343R, the Canadian Highway Bridge Design Code, AASHTO Guide Specifications for Horizontally Curved Bridges, and AASHTO-LRFD Bridge Design Specifications specify certain limitations to treat a horizontally curved bridge as a straight one in structural design. However, these limitations proved to be inaccurate in estimating the structural response. To investigate the accuracy of these limitations, a series of curved concrete cellular, multi-box, and solid-slab bridge configurations were analyzed in this study using finite element modeling to investigate their behavior under dead loading. The major internal forces developed in the members were determined and then compared with those obtained for straight bridges of identical configuration. The stipulations made in bridge codes for treating a curved bridge as a straight one were proven unsafe when correlated with the finite element analysis (FEA) results. As such, sets of empirical expressions were developed to determine such limitations more accurately and reliably. [ABSTRACT FROM AUTHOR]

In recent years, horizontally curved bridges have been widely used in congested urban areas, where multilevel interchange structures are necessary for modern highways. In bridges with light curvature, the curvature effects on bending, shear, and torsional stresses may be ignored if they are within an acceptable range. Treating horizontally curved bridges as straight bridges with certain limitations is one of the methods to simplify the design procedure. Bridge design specifications and codes have specified certain limitations to treat horizontally curved bridges as straight bridges. However, these limitations do not differentiate between bridge cross section configurations, in addition to being inaccurate in estimating the structural response. Moreover, these specifications were developed primarily for the calculation of girder bending moments. To investigate the accuracy of these limitations, a series of horizontally curved, braced concrete slab-over steel I-girder and slab-on-concrete I-girder bridges were analyzed, using three-dimensional finite-element modeling, to investigate their behavior under dead loading. The major internal forces developed in the members were determined, namely, girder longitudinal bending stresses, vertical deflections, vertical support reactions, and bridge fundamental flexural frequencies for different degrees of curvature, span length, bridge width, and span continuity. Empirical equations for these straining actions were developed as a function of those for straight bridges. The stipulations made in bridge codes for treating a curved bridge as a straight bridge were then correlated with the obtained values from the finite-element modeling. Results proved that such code limitations were unsafe. Based on the data generated from this parametric study, sets of empirical expressions were developed to determine such limitations more accurately and reliably. [ABSTRACT FROM AUTHOR]

Driving vehicles with one or more passive trailers has difficulties in both forward and backward motion due to inter-unit collisions, jackknife, and lack of visibility. Consequently, advanced driver assistance systems (ADAS) for multi-trailer combinations can be beneficial to accident avoidance as well as to driver comfort. The ADAS proposed in this paper aims to prevent unsafe steering commands by means of a haptic handwheel. Furthermore, when driving in reverse, the steering-wheel and pedals can be used as if the vehicle was driven from the back of the last trailer with visual aid from a rear-view camera. This solution, which can be implemented in drive-by-wire vehicles with hitch angle sensors, profits from two methods previously developed by the authors: safe steering by applying a curvature limitation to the leading unit, and a virtual tractor concept for backward motion that includes the complex case of set-point propagation through on-axle hitches. The paper addresses system requirements and provides implementation details to tele-operate two different off- and on-axle combinations of a tracked mobile robot pulling and pushing two dissimilar trailers. [ABSTRACT FROM AUTHOR]