This English translation of the successful French edition presents the conception and design of steel and steel-concrete composite bridges, from simple beam bridges to cable-supported structures. This book focuses primarily on road bridges, emphasizing the basis of their conception and the fundamentals that must be considered in order to assure structural safety and serviceability, as well as highlighting the necessary design checks. The principles are extended in later chapters to railway bridges as well as bridges for pedestrians and cyclists. For these structures, particular attention is paid to consideration of the dynamic performance. The assembly of the steel and the placing of the reinforced or pre-stressed concrete slab are explained while emphasizing their influence on the design of the structure.