كتاب Design and Construction of Cable-Stayed Bridges in the Czech Republic

Design and Construction of Cable-Stayed Bridges in the Czech Republic Jiri Strasky, Ph.D. Consultant T.Y. Lin International San Francisco, California For 22 years, Jiri Strasky worked as chief design engineer with Dopravni Stavby, Olomouc-a leading state company for the construction of bridges in Czechoslovakia. In this position, Dr. Strasky was responsible for the development and design of precast segmental, stress-ribbon and cablestayed bridges. After political changes in 1989, he opened his own design office and was appointed professor of concrete structures at the Technical University of Brno. In the United States, he served as a special consultant in the design of the first stress-ribbon bridge built in North America and for the recently completed Wisconsin Avenue viaduct. For his design work, he received the FritzSchumacher Prize from the University of Hannover, Germany, and an Award of Excellence from the Portland Cement Association. Currently, Dr. Strasky is a consultant with T.Y. Lin International in San Francisco. 24 The author discusses the design, analysis and construction of two innovative precast, prestressed concrete cable-stayed bridges recently built in the Czech Republic. The first bridge was built across the Elbe River near Podebrady and the second bridge was built over a major railroad junction in Prague- Vrsovice. The decks of these bridges comprise a spine box girder assembled of precast, match-cast segments and cast-in-place overhangs supported by precast concrete struts. External prestressing was used to strengthen the deck. To confirm the validity of the design, a static and dynamic analysis of the structural system was conducted together with model testing. The author shows how this system, with some modification, can be applied to other cable-stayed and segmental concrete bridges. T wo cable-stayed bridges using precast, prestressed concrete segmental construction (see Figs. 1, 2 and 8) were recently erected for a freeway in the Czech Republic. One bridge was built across the Elbe River near Podebrady while the other bridge was built over a major railroad junction in Prague-Vrsovice. The bridges combine the high quality and speed of construction of precast segmental structures with the structural continuity of cast-in-place concrete (see Figs. 3 and 4). The deck of the main span and approach spans of these bridges consists of a spine box girder assembled of precast, match-cast segments and cast-in-place overhangs supported by precast concrete struts. Both bridges are suspended in the bridge axis on composite steel pylons that are fixed into the deck (see Fig. Sa). The stays are arranged in a semi-fan shape and are formed by strands grouted in steel tubes. The approach spans are posttensioned (suspended) on draped external tendons placed in the bridge axis (see Fig. Sb). The precast concrete segments were erected in progressive cantilevers by a special crane moving on the deck. PCI JOURNAL
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