Design of a specific bituminous surfacing for orthotropic steel bridge decks : application to the Millau Viaduct

This paper presents a rational approach for the performance-based design of bituminous wearing surfacings on orthogonally anisotropic steel bridges. Basically, the behavior of bituminous surfacings on steel orthotropic decks, under heavy truck traffic and environmental conditions, is highly complex. Both the geometry of the structure and the very high flexibility of metallic plates make the deformations and stresses very severe in steel bridge surfacings. In particular, the repeated loading make the fatigue strength be an important parameter for the design of such bituminous wearing courses. In addition, these specific surfacings must also have durability over the expected temperature range: it must beresistant to thermal cracking at low temperature and to rutting at high temperature. The technical studies led in parallel to the construction of the Millau Viaduct (France) –the tallest bridge in the world– have provided in particular the opportunity of new progress in the development of appropriate laboratory testing equipment and of original polymer-modified surfacing. Indeed, APPIA pulled the socks up and led a comprehensive research program including both a large laboratory testing campaign and a Finite Element analysis so as to develop a handy tool for design of plate surfacings. Eventually, as regards the realization of this one-off work, the bringing into play of considerable resources made APPIA succeed in delivering within the deadlines a surfacing of the highest standard for the Millau Viaduct.