Experimental testing and FE model validation of a historic high-rise building in Milan

In relation to Reinforced Concrete (RC) tall buildings built in the Fifties and Sixties of the 20th Century, it has acquired importance, in the last few years, to analyze the capabilities to withstand various kinds of environmental risks, defined according to actual parameters. The provisions prescribed by new structural design codes practiced today, indeed, have substantially changed both design actions and verification procedures as well, if compared to the building criteria in use in the past. The opportunity offered by the re-analysis of the building that houses still nowadays the technical offices of the Milan Municipality, constructed in Milan in the Sixties and classified as of strategic importance, has offered a good basis for the discussion of all this matter. In particular, it has shown the complexity of the reference framework of building rules which have to be considered. Also, it leads to an interesting debate about the decision of designing and planning suitable interventions, in relation to the basic issue of structural safety. A complete set of experimental tests was performed on the structural materials, such allowing to reach a comprehensive level of knowledge (level 3 for the Italian Building Code), which corresponds to a confidence factor equal to 1. Moreover, a monitoring system for the recording of accelerations has been installed to the structure in order to characterize the dynamic behavior of the building in terms of frequencies and mode shapes. In parallel, also static monitoring systems were installed at some critical locations for the measurement of displacements and strains. The wide set of experimental data which has therefore come from the dynamic testing of the building has allowed the calibration of an elastic numerical model with reference to the fundamental period and, in general, to the global stiffness properties. Through the model it has been possible to characterize the seismic response of the building, in view of a correct evaluation of the available safety margins and of possible upgrading interventions.