A STRUCTURAL INSIGHT FOR THE PRESERVATION OF MARINA CITY TOWERS IN CHICAGO

In relation to reinforced concrete high-rise buildings built in the Fifties and Sixties of the 20th Century in Chicago, it has acquired importance the re-analysis of their structural performance according to the provisions prescribed by new structural design codes, that have substantially changed both design actions and verification procedures. In this paper the case study offered by the two Marina City towers is analyzed. Marina City towers (1959 - 1967) designed by Bertrand Goldberg represent an important architectural landmark in the Chicago skyline. At the time of their completion, the Marina City towers were the tallest reinforced concrete apartment buildings in the world. Typically, this kind of high-rise buildings was designed for withstanding vertical and wind lateral loads only. Although the seismic hazard is classified as low in the area of Chicago, the design seismic forces could become more severe than wind actions for historical tall buildings, due to the limited ductility resources available in the structural elements, mainly in the shear walls. The aim of this work is the analysis of these towers from a structural point of view considering three different codes: the Chicago Building Code of the 1950s, the current Chicago Building Code and the ASCE7-10.