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  • Underground tunnels in seismic areas

    Analytical and numerical models of the structural safety of an underground tunnel under seismic ac- tions are discussed. Three procedures are compared: the first is analytical, in two versions (Penzien-Wu 1998 and Penzien 2000), and the others are numerical, referring to the computer codes Flush and Flac, in two-dimension space. The analytical procedure considers the soil as homogeneous. The tunnel cross-section is circular and this allows an application to the underground railway of Naples, which has effectively this structural cross-section. When conditions are equal, the three procedures offer similar results in terms of maximum values of internal force components and in fair agreement as distribution along the wall. However important effects are highlighted next to soil discontinuities, in particular in seismic conditions.

    The complete paper is available in Italian only.

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  • A methodology for the evaluation of site effects in an area of Lombardia Region (Italy)

    In the paper the application of a methodology for the evaluation of site effects in an area of Lombardia Region (Italy) is shown. The objective of the project was to develop a methodology that may be easily repeated, to take into account site effects in urban planning.
    Therefore, a series of geologic, geomorphologic, geotechnical and geophysical analyses have been carried out, to identify the areas affected by site effects and to characterize the litho-technical units. The expected seismic inputs have been individuated and numerical analyses using one-dimensional (1D) code, analyzing single soil columns, and two-dimensional (2D) codes, working with finite or boundary elements on sections, have been done. The results, in terms of amplification coefficients, as a ratio between spectral intensity calculated in the periods of 0.1-0.5s and 0.5-1.5s of output and input, give elements for planning, both for urban general choices and for building design. In fact the results of all the analyzed situations, provide some correlations between the geometric and geophysical characteristics of the sites and the values of the amplification coefficients. These correlations could be used as a tool for extrapolations in similar situations, when only the geologic, geophysical and geotechnical characteristics of a site are known.
    The procedure provides three level of widening: the 1° level, a qualitative analysis, gives the identification of the areas characterized by the local effect. The 2° level, through a semi-quantitative analysis, gives, when the geologic, geophysical and geotechnical characteristics of a site are know, the possible level of the expected amplifications, using the performed correlation curves. The 3° level, characterized by a quantitative analysis, necessary during the project design of strategic build or in the case in which the application of the 2° level show the inadequacy of the seismic code, gives a the response spectra applying during the project design phase
    The proposed procedure, furthermore, is characterized by a modularity that allows its implementation and up- dating.

    The complete paper is available in Italian only.

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  • A new design strategy to control the torsional seismic response of isolated asymmetric-plan systems

    A new design strategy to control the torsional seismic response of isolated asymmetric-plan systems by using dissipation devices is herein presented. Effects of the plan-wise distribution of supplemental damping on torsionally dynamic behaviour have been investigated by using modal analysis techniques in the state space representation. Numerical analysis leads to the optimal plan-wise allocation of damping resources on varying the dynamic characteristics of the asymmetric-plan system. Results are verified by both applying H2 and H norm methods and numerically integrating the dynamic equations to recorded seismic events.

    The complete paper is available in Italian only.

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  • Effective procedures to evaluate the seismic vulnerability of monumental buildings

    In this paper, a preliminary study about effective procedures to evaluate the seismic vulnerability of monumental buildings of particular typology (churches) is proposed. The method is able to work out the seismic- acceleration levels related to the different limit states, before and after the possible interventions. This evaluation, feasible for each different macroelement /1/ that a church is typically made of, is in agreement with the seismic-safety procedures proposed by the recent Italian Decree, in case of local mechanisms in masonry existing ordinary buildings. The application of the methodology to two case studies is presented: the church of S. Giovanni Battista in Colletorto (Campobasso, Italy), damaged by the 2002 earthquake, and the church of S. Lazzaro in Foligno (Perugia, Italy), struck by the 1997 seismic events.

    The complete paper is available in Italian only.