Design principles of surfacings on orthotropic steel bridge decks

This dissertation describes the research into surfacings of orthotropic steel bridge decks. The motive for this research is the frequently reported problems of this type of structures including cracking and rutting of surfacing materials and fatigue related cracks in the steel plate. An intensive experimental program was carried out on three wearing course materials, namely mastic asphalt, guss asphalt and an open synthetic material. The program also included on a bituminous based membrane material. The results of the experimental program were analysed to characterise the complex mechanical behaviour of the different materials. Within the framework of this research, models that describe the response of the surfacing materials were developed, including a newly developed unified model that describes the time-temperature characteristics of many road materials. Furthermore, constitutive relations for elastic as well as inelastic response of the materials were developed. All the developed models were implemented in the Finite Element System CAPA-3D. For verification of the different models results of laboratory tests and full-scale experiments in the LINTRACK APT facility were used. Furthermore, a scientific approach in which the non-linear response of the materials, the geometry and the load are well presented, was used to give an insight into the interaction between the different components of the structure and the vehicle at different temperatures. Because this scientific approach is too sophisticated and expensive for routine analyses and design of the structure, a practical design concept is proposed. In this concept, the geometry and the load are well presented, but the material behaviour is simplifiedCivil Engineering and Geoscience

Estimation of fatigue characteristics of asphaltic mixes using simple tests

A simplified procedure for estimation of fatigue characteristics of asphaltic mixes is presented. The procedure requires the determination of the so-called master curve (Le. the relationship between the mix stiffness, the loading time and the temperature), the asphalt properties and the mix composition. It is shown that the master curve does not only give information about the variation of the mix stiffness, the loading time and the temperature, but also on the fatigue behaviour of asphaltic mixes. This information can reliably be obtained from rather simple tests, which can be performed in any road-engineering laboratory. Procedures of the determination of the fatigue characteristics of asphaltic mixes from simple tests are of special interest in mix design procedures where the quality of various mixes with respect to fatigue and crack resistance has to be evaluated. It is obvious that such a procedure is also extremely attractive for specification and pavement evaluation purposes. An insight is provided as to how the fatigue parameters for an asphaltic mix can be estimated using the Wohler approach.Laboratory for Road and Railroad ResearchCivil Engineering and Geoscience