Orthotropic decks - developments and future outlook

Bridges with steel orthotropic decks, first introduced in the 1950s in Germany, have been subsequently built in other countries, with several thousand of such structures now in service throughout the world, The performance record of orthotropic decks has been satisfactory, excepting occasional fatigue cracking which had occurred on some decks built in the 1960s and 1970s, mainly caused by inappropriate details and fabrication defects. Specific causes of such failures are discussed. Developments of design methods for orthotropic decks are discussed. For basic design simplified approaches, such as the Pelikan-Esslinger method, are generally used. The applicability of the classical (Wohler's) fatigue theory is limited. Therefor current design specifications permit empirical fatigue safety assessment by conformance with approved geometric standards. Due to their light weight, durability and load carrying capacity, orthotropic decks have a promising future being indispensable in the super-long span bridges. Because of their capability for being structurally integrated with the main members of the existing steel bridges, orthotropic decks are also excellently suited for replacing the deteriorating concrete decks. In the U.S. nearly 40% of highway bridges are now considered structurally deficient" or, functionally obsolete", with failed concrete decks accounting for about two-thirds of the deficiency cases. Several major U.S. bridges have recently received new orthotropic decks. Special problems encountered with redecking are discussed.