40 Years History about Structure, Design and Construction of the First Steel Orthotropic Bridge in Sofia

Abstract

The most spectacular and large bridge in Bulgaria and one of the largest in South-East Europe bridge in Sofia was put into operation at the beginning of October 1983. The bridge perform a multi-span, prestressed reinforced concrete construction with a total length of 2114 m, a total width of 21.5 m and an average height above the ground of about 10 m. This important, effective and aesthetic bridge serves as a connection between the busiest input-output highway and the airport of Sofia. It ensures a convenient access to some highways, railways, streets and the airport. As a result of this requirement, the erection of the prestressed reinforced concrete bridge is not allowed to cross the railway between Sofia and Varna. So, a 90 m long middle steel part was designed to cover two spans of 45 m each in the multi-span bridge structure. In transverse direction the orthotropic bridge, consists of two individual parallel triple-box decks parts, which carry the traffic in two opposite directions. Each deck has a 7.5 m wide roadway with two lanes. The bridge is analysed as a frame structure using the finite element method. The design parameters of the bridge are verified by static and dynamic tests. The steel structure is designed as a two-span continuous beam with a box cross-section and an orthotropic deck. The paper deals with the most important aspects which consider the design approach and the construction process of this large, steel orthotropic bridge in Bulgaria.