IBSBI 2014, October 16 -18, 2014, Athens, Greece FOUNDATION OF A LIGHTWEIGHT STEEL ROAD BRIDGE ON PEAT Chrysanthos Maraveas 1 , Konstantinos Miamis 2 and Konstantina Tasiouli 3 1,2,3 C. Maraveas Partnership, Consulting Engineers, Greece 1 University of Manchester, School of Mechanical, Aerospace & Civil Engineering, UK e-mail: c.maraveas@maraveas.gr, steelstru@maraveas.gr, structures@maraveas.gr ABSTRACT: This paper presents the foundation study of the new road bridge in the valley of “Tenagi”, Kavala, Greece. Selection of a lightweight superstructure was mandated by the region’s poor foundation conditions (peat). Soil improvement techniques, such as deep soil mixing as well as construction of vertical sand drains and preloading embankments were also proposed. KEY WORDS: Peat; Sand Drains; Soil Deep Mixing; Soil Improvement; Through-Truss Steel Bridge. 1 INTRODUCTION Foundation of bridges on weak soils has always proven to be a great challenge for civil engineers, especially when the superstructure transfers heavy loads to the foundation system. In certain occasions, the geotechnical conditions determine the selection of the load-carrying system. This is the case for the new lightweight steel road bridge near Kavala, Greece, which will replace an old reinforced concrete one that is no longer in service due to failure (excessive rotation) of the foundation of the pier. Besides minimizing the weight of the bridge, techniques to improve the existing soil (peat with very poor geotechnical characteristics) were necessary to complete the foundation design. 2 DESCRIPTION OF THE BRIDGE 2.1 General Information The studied steel road bridge is located in the valley of “Tenagi”, Kavala (northern Greece) and will serve as an overpass for a 40m wide aqueduct canal. The 67m long, 4.75m wide single-span bridge is considered of vital importance for the region, as it will facilitate the crossing of agricultural vehicles and will dramatically decrease transportation times among the local farmlands. 2.2 Description of the superstructure The poor foundation conditions, which are discussed below, mandated the selection of a lightweight structural system for the bridge. After considering