Design of a Specific Bituminous Surfacing for the World's Highest Orthotropic Steel Deck Bridge: France's Millau Viaduct (05-2069)**
Bernard Heritier, Appia, France
Francois Olard, Eiffage Travaux Publics, France
Frédéric Loup, Appia, France
Serge Krafft, Appia, France

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, they must be resistant to thermal cracking at low temperatures and to rutting at high temperatures. The technical studies led in parallel to the construction of the Millau Viaduct (France) –the highest bridge in the world– have provided in particular the opportunity of new progress in the development of appropriate laboratory testing equipment and of an original polymer-modified surfacing. A comprehensive research program including both a large laboratory testing campaign and a finite element parametric study was performed in order to develop a handy tool for design of plate surfacings.