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6th International Conference on Accelerated Pavement Testing , NANTES, FRANCE, 27-/09/2021 - 29/09/2021; The concept of truck platooning is to take advantage of the connectivity technologies and automated driving support systems to link trucks in close formation (convoy) in order to increase transport efficiency, reduce fuel consumption and gas emissions while improving road safety. However, closely guided trucks following each other could have a different impact on road structures than the usual truck traffic. Notably, different studies with traffic simulators highlight the significant effect of the wander pattern of traffic on the damage observed on test road structures. On the other hand, the positioning systems could offer the opportunity to choose an optimized wander pattern of the trucks within the platoons, especially designed to mitigate the overall damage. In this context, the study reported in this paper addresses, through numerical simulations, the multi-loading effects of truck platoons on road structures for different configurations of wander patterns. The aggressiveness of these patterns is evaluated on the basis of the viscoelastic response of the pavement structures (strain field) computed using software ViscoRoute\textcopyright 2.0. Finally, recommendations on the choice of wander pattern configurations to be tested on APT facilities are proposed.

26th PIARC World Road Congress, ABU DHABI, EMIRATS ARABES UNIS, 06-/10/2019 - 10/10/2019; In Europe, regulation on weights and dimensions of trucks are prescriptive, rather than performance based, as it is introduced in some other countries (Australia, Canada, South Africa). The performance based standards (PBS) allow more flexibility in the vehicle design and optimize their performances with respect to the infrastructure constraints. Thus, PBS facilitate innovation and industrial progresses, while mitigating adverse effects on infrastructure and road safety. Therefore, the European project FALCON (2016-2018), supported by CEDR proposed a methodology for the development of performance-based criteria and future PBS in Europe. This paper presents the approach developed for bridges and pavements criteria assessment and implementation. For bridges, an exhaustive catalogue of structures has been developed, made of a pool of influence lines representative of the European bridge stock. Then, several design traffic load models used in the EU Member States, including the load models proposed in the Eurocode EN1991-2 Traffic loads on road bridges have been applied and compared on these structures. The governing load models and structures for the current traffic loads have been determined. This enabled proposing a performance-based standard approach, using either a bridge formula or a well-chosen upper limit of the load effects induced by the authorized heavy vehicles. For pavements, a catalogue representing the standard, bituminous and rigid, European pavement structures was developed. The various wears have been reviewed, and design criteria have been listed. The individual impacts of the vehicles of a reference fleet have been calculated, making possible to rank them in terms of aggressiveness for the pavement. That paves the way for a future PBS approach of heavy vehicle type approval, or a revision of the European Directive 2015/719 on commercial vehicles weights and dimensions. It also opens new perspectives to develop a SIAP (Smart Infrastructure Access Programme) to be implemented on the Trans-European road Network, as a tool to enhance the durability of the existing infrastructure with the lowest restrictions on the road freight movements.

Some ageing bridges exposed to heavy traffic loads or abnormal loads may have critical details, either against extreme loads or in fatigue. Old bridges were designed with design codes and load models which are now exceeded by the authorized vehicle loads. Therefore, keeping the bridge safety and reliability at an acceptable level requires periodical reassessments of some structural parts, using updated traffic data, e.g. weigh-in-motion (WIM) data. For extreme loads and current ultimate limit states, extrapolated maximum axle, vehicle or total loads, depending on the considered effect and influence line length, are used to assess the maximum load effects which may be exceeded with a given probability. They are compared to the design loads affected of the partial safety factors. For fatigue limit state and lifetime assessment, the updated traffic loads, if available, or some estimation based on similar traffic flow, are used to calculate expected lifetime with the Miner's law and fatigue resistance (S-N) curves. These lifetimes are compared to the required ones, taking into account the elapsed bridge lifetime. In several country, like in France, abnormal loads regulation was made more flexible in order to avoid long administrative delay to get the permits, and up to some gross vehicle weight limits, the permit can be obtained very easily and quickly on-line through Internet. Some routes are allowed to different classes (1 to 3 in France) of abnormal loads, up to 120 t. Before labelling a route for a given class, all the sensitive bridges should be checked. In 2017, the prefect of Normandy asked to open the bridge of Normandy to the class 3 abnormal loads (120 t). The bridge concessionaire and the Ministry of Transport appointed IFSTTAR and a consulting company (Quadric) to perform some assessment of the impact of these abnormal loads on the bridge orthotropic deck lifetime in fatigue. The paper will present some of the sensitive bridges and details, a quick review of abnormal loads or load models, the trend of heavy vehicle weight limits in the EU, and then the impact of these loads on existing bridges. A special focus will be done on the study carried out for the fatigue of Normandy bridge under current and abnormal traffic loads, and how the abnormal loads can reduce the bridge lifetime. These results are useful for the decision makers to take the final decision on abnormal load authorization.

The local authorities asked in 2017 the concessionaire of the bridge of Normandy (CCISE), a 856 span length cable stayed bridge, to study the feasibility opening it to abnormal loads up to 120 t. The CCISE asked the advice of the bridge designer, M. Virlogeux, and to IFSTTAR, to measure the current traffic loads on the bridge, in operation since 1994, to assess the fatigue lifetime under this real traffic loads, and to estimate the potential lifetime reduction if the abnormal loads up to 120 t were allowed. IFSTTAR and Cerema installed a bridge WIM system (SiWIM) in July 2017 on the bridge to measure the traffic loads over more than 7 months. These data allowed assessing the expected lifetimes of the most sensitive details of the orthotropic steel deck. These lifetimes were compared with those obtained under 3 other traffics recorded on other French motorways. Then the fatigue damage induced by 4 conventional abnormal loads (2 cranes of 96 and 108 t, and to vehicles C1 and C2 of 94 and 120 t) was calculated. Finally, the lifetime reduction if each of these 4 abnormal loads cross the bridge twice a day was assessed., Les autorités locales ont demandé en 2017 au concessionnaire du pont de Normandie (CCISE), ouvrage haubané de 856 m de portée, d'étudier la possibilité d'ouvrir le pont à des transports exceptionnels jusqu'à 120 t. La CCISE a demandé l'avis du concepteur de l'ouvrage, M. Virlogeux, et à l'IFSTTAR de mesurer les charges de trafic sur le pont en service depuis 1994, d'estimer la durée de vie en fatigue et sa réduction potentielle si les convois jusqu'à 120 t étaient autorisés. L'IFSTTAR et le Cerema ont installé un système de pesage par pont instrumenté (SiWIM) en juillet 2017 pour mesurer les charges de trafic pendant plus de 7 mois. Ces données ont permis de calculer les durées de vie des détails les plus sensibles du platelage de la dalle orthotrope. Ces durées de vie ont été comparées à celles obtenues avec 3 autres trafics autoroutiers français. Ensuite le dommage en fatigue induit par 4 convois exceptionnels (2 grues de 96 et 108 t et 2 convois conventionnels C1 et C2 de 94 et 120 t) a été calculé. Finalement la réduction de durée de vie du pont a été estimée si chacun de ces 4 convois passaient 2 fois par jour.

TRB, Transportation Research Board Annual Meeting, WASHINGTON, ETATS-UNIS, 13-/01/2019 - 17/01/2019; Due to a request to open the Normandy bridge in France to abnormal loads, some detailed investigations have been carried out on the current traffic loads, and on the expected fatigue lifetimes, with and without the abnormal loads. This long span cable-stayed bridge is made of a steel orthotropic deck, quite sensitive to fatigue under traffic loads. Using the simplest standardized fatigue load model of the Eurocodes (LM3 of Eurocode 1991-2) is much too conservative and leads to unrealistic calculated lifetimes of a few years. Therefore, a real traffic load assessment was performed with a Weigh-in-Motion (WIM) system. A bridge WIM (B-WIM) system has been installed on the bridge, and the traffic loads were measured continuously over 7 months. The influence lines of the most sensitive details, mainly at the welds between deck plate and longitudinal stiffeners, at various transversal locations, were re-calculated with a 3-D finite element model (FEM), and compared to former measured influence lines. Fatigue lifetimes were assessed using the Miner's law, using successively a simplified load model made of a standard tridem axle, the measured traffic loads on the Normandy bridge, some measured traffic loads on other French motorways, and finally with a superimposition of the current traffic loads and the expected abnormal loads. The transverse location of the wheels on the deck has a great influence on the fatigue damage. With all these results, pratical recommendations were delivered to the bridge concessionary about the acceptability of the abnormal loads.