A NEW LIGHTWEIGHT STEEL BRIDGE FOUNDED IN PEAT Optimal Design and Soil Improvement

This paper presents the planned design for a new steel road bridge in the Tenagi valley, Kavala, Greece. The plans are for a single span steel truss trough bridge with a span of 67 m over an irrigation channel. The new bridge will replace an existing reinforced concrete one that is no longer in service due to excessive rotation of its single pier and deck failure. The major challenge associated with the design of the new bridge is the poor soil characteristics in the region. The soil is composed of peat to a depth of over 200 m. Optimization of the type, shape, and size of the bridge superstructure is critical in order to minimize soil intervention. In this article, the effects of several types of deck (a reinforced concrete deck, a fiber reinforced polymer deck, and a steel deck are considered) on the weight of the steel truss are examined. Shape optimization of the truss is conducted with the truss height as a variable. Beyond minimizing the weight of the bridge, soil improvement techniques such as deep soil mixing and the preloading of embankments must also be implemented to minimize settlement and increase the bearing capacity of the soil.