Development of Long Span Arch Bridges

This paper gives a summarized account of development of long span concrete arch bridges,puts forward the conception of both the theoretic ultimate and theoretic feasible span length of arch bridges and specifically,provides the theoretic feasible span length respectively for the concrete and steel arch bridges.Taking the newly-built Krka Bridge in Croatia as the proto- type,the paper also proposes a type of new structure of steel and concrete composite truss arch. It is found in the comparison of the structure with only the concrete arch and steel truss arch,the structure of the steel and concrete composite truss arch has certain advantages in aspects of its structural performance,economy and the structure is a one that deserves research in a further way.