<p>Orthotropic deck structures are used in many steel bridges. Due to the typical detailing applied as around 1970, a significant number of deck structures constructed in that period suffer from fatigue damage. In many countries cracks have been detected, in particular in the weld between the deck plate and the trapezoidal stiffener. These cracks tend to grow relatively slowly, but are difficult to detect at an early stage because they initiate from inside the trapezoidal stiffener.</p><p>This paper presents a model with which the growth of these cracks can be predicted. The model is aimed at the growth rate prediction of through-thickness cracks that can be detected by visual inspection, but that do not have a risk of fracture, which would affect the traffic safety. Stresses are extracted from a detailed finite element model of the entire deck. A second, local finite element model including the crack is used as the basis of a fracture mechanics model. The growth rate determined with the model is calibrated and validated with measured cracks in various bridges.</p><p>The novel model can be used in daily engineering practice. It can serve to determine inspection intervals for orthotropic bridge decks. It can also serve to support decisions of repairing detected cracks or to determine the effectiveness of strengthening measures such as the addition of a high strength concrete overlay. The model has been successfully applied to 6 large existing bridges in The Netherlands.</p>
Reinforced concrete is an inherently non-linear material with non-linear compressive behaviour, concrete cracking and reinforcement yielding altering the stiffness and causing redistribution of forces within statically indeterminate structures. A practical design approach is described that has been developed to ensure robust computation of serviceability limit state and ultimate limit state demand in line with Eurocode BS EN 1992, including explicit modelling of material and geometric non-linearities and construction imperfections. The approach uses the MAT_CONCRETE_EC2 material model within the LS-DYNA finite-element analysis package and has been extensively used during the detailed engineering design of the concrete gravity substructure for the White Rose Extension Project off the coast of Newfoundland, Canada. The material model and validation of its behaviour in accordance with the Eurocode standard are described, along with other typical engineering applications where the approach may be of benefit. Specific benefits and implementation challenges encountered during the design process are also highlighted with a non-linear buckling assessment case study.
In order to address orthotropic steel deck fatigue problems typically encountered in the Netherlands, such as longitudinal deck plate to trough cracks, in-situ poured High Strength Concrete (HSC) deck strengthening has recently been used. This method has been further developed by using an innovative Prefabricated Ultra High Performance Fibre Reinforced Concrete/Béton Spécial Industriel ® (UHPFRC/BSI ® ) Slab solution.The prefabricated slabs can be installed faster than pouring and curing concrete in-situ. Also, if a deck plate repair is required, it can be made post deck strengthening using traditional welding methods as the presented solution is less sensitive to heat than the in-situ HSC solution, which utilises a heat sensitive Epoxy-Bauxite bonding layer between the concrete and steel deck. The presented solution has been used by Eiffage on one bridge in France (Pont de Illzach, Alsace) and it has been developed for the Ewijk Bridge. This development, documented in this paper, constitutes a significant change in terms of bridge typology and loading.
<p>A common problem in steel bridges is fatigue of orthotropic decks due to heavy traffic demands. Whilst replacing the asphalt with a high strength concrete overlay can solve this problem, it imposes significant additional self-weight. This additional self-weight often requires strengthening of the superstructure which in turn can result in long execution times with associated hindrance and costs. As no existing method addressed these issues Arup engineers developed an innovative solution for Rijkswaterstaat (RWS), the Dutch Highways Authority. The new solution consists of bolting steel plates to the orthotropic steel deck, stiffening it for fatigue. Arup and RHDHV work in a joint venture, the Managing Contractor, on the renovation of steel bridges for and with RWS.</p>
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