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  • Special Issues

    • CRITICAL DISCUSSION ON SEISMIC DESIGN CRITERIA FOR CROSS CONCENTRICALLY BRACED FRAMES

    Silvia Costanzo, Mario D’Aniello, Raffaele Landolfo, Attilio De Martino

    Recent studies show that the application of EC8 design procedure for X-CBFs, leads to uneconomical and ineffective structural systems, characterized by massive structural members,  large lateral overstrength  and poor plastic engagement.  In this  paper, the EC8- compliant design procedure is summarized and critically discussed also comparing  the EC8 detailing  rules with those recommended  in US Code. In order to assess the influence of the different  codified  requirements,  a six-storey  residential  building  is selected  as benchmark case  and  alternatively   designed  according  to  both  European  and  US  code.  Nonlinear dynamic analyses are performed and the seismic performances of EC8 and AISC-compliant frames are discussed and compared.

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  • Special Issues

    • REMARKS ON THE APPROACHES FOR SEISMIC DESIGN OF MOMENT-RESISTING STEEL FRAMES

    Claudio Bernuzzi, Claudio Chesi, Davide Rodigari, Riccardo De Col

    Nowadays, moment-resisting steel frames are one of the most attractive typologies of structural systems resisting to earthquakes. According to the Eurocode for seismic design (EC8) four alternatives can be used, that differ in the type of seismic analysis and for the verification approaches. A research project is in progress at the Politecnico di Milano on the investigation of these seismic design methods. At first, this paper briefly discusses these approaches. Then attention is focused on a case-study, a one-bay four-stories rigid frame for which nine different seismic inputs have been defined. For each of them, the four admitted methods of seismic analysis are applied. The research outcomes underline nonnegligible differences from a structural point of view, suggesting the need of a deeper investigation of the range of applicability of the single methods.

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  • Special Issues

    • BETWEEN INNOVATION AND INTUITION: PATENTS FOR ANTI-SEISMIC BUILDINGS IN THE FIRST 50 YEARS OF KINGDOM OF ITALY

    Stefano Cocco

    This study proposes an analysis of the anti-seismic buildings patents granted in the first 50 years after the unification of Italy. The purpose is to expand and systematize the comprehensive knowledge framework in this particular field through the technological scenario reconstruction, referring to the patents for the anti-seismic residences. This particular field has been chosen because of the will to trace back, within a specific time span of the recent past, any potential technological precursors of the most common construction solutions in the Twentieth century. Among the identified solutions, albeit there are few of them, it is possible to trace back isolation systems, metal frame structures and reinforced masonry systems.

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  • Special Issues

    • ASSESSMENT OF DYNAMIC INCREASE FACTORS FOR PROGRESSIVE COLLAPSE ANALYSIS OF STEEL FRAMES SUBJECTED TO COLUMN FAILURE

    Massimiliano Ferraioli, Angelo Lavino, Alberto Mandara

    The nonlinear static force method and its dynamic increase factor (DIF) were investigated analysing steel frames subjected to column failure. The assessment was performed in terms of the ability of the nonlinear static method to predict the peak structural response observed in the dynamic analyses. The values of dynamic increase factor thus obtained were expressed as a function of the vertical displacement in the location of column removal.
    Variability in these results is then assessed showing that they vary more significantly depending on variables such as the number of spans, the location of column removal, the number of  building stories and the level of seismic design load. The values obtained were finally compared with the formulation of the dynamic increase factor proposed by GSA and based on the ductility factor. It was observed that using standard DIF formulae might lead to inaccurate results. In fact, these empirical formulae are based on the hypothesis of a constant value or a monotonic decreasing with ductility. On the contrary, in the cases where the hardening behavior of the catenary action is fully developed, the analytical curve of DIF first decreases and then increases with ductility.

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  • Special Issues

    • EFFECTIVENESS OF MULTI-MODE PUSHOVER ANALYSIS PROCEDURE FOR THE ESTIMATION OF SEISMIC DEMANDS OF STEEL MOMENT FRAMES

    Massimiliano Ferraioli, Angelo Lavino, Alberto Mandara

    A multi-run and multi-mode pushover procedure for the approximate analysis of the seismic response of steel moment-resisting frames is developed and evaluated. A set of generalized force vector is defined as the combination of modal forces in order to reproduce the inertial load pattern applied to the structure when the maximum drift occurs under the earthquake ground motion. The proposed procedure is easy to implement and reduces the computational cost when compared to nonlinear dynamic analysis and adaptive nonlinear static procedures. Furthermore, it overcomes the disadvantages in the use of the modal combination rules commonly used. The paper presents a parametric analysis of the response of steel moment resisting frames under various earthquake ground motions with increasing peak ground accelerations. The advantages of the proposed procedure compared to other nonlinear static procedures in literature are highlighted.

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  • Special Issues

    • SEISMIC UPGRADING OF RC STRUCTURES WITH ONLY BEAM CONNECTED STEEL PLATE SHEAR WALLS

    Eduardo Totter, Antonio Formisano, Francisco Crisafulli, Federico Mazzolani

    Steel Plate Shear Walls (SPSWs) connected to the boundary frame beams only are suitable structural systems to resist lateral loads. These systems allow for designers to avoid the high flexural demands over columns imposed by conventional SPSWs connected to both beams and columns of the surrounding frame. They can be successfully applied for seismic upgrading of existing RC structures to provide them higher levels of strength, ductility and energy dissipation capacity. This paper presents a numerical assessment of the seismic response of an existing RC structure upgraded with only beam connected SPSWs. The structure, designed for resisting vertical loads only, was erected in the district of Bagnoli in Naples. The used numerical approach is based on the simplified strip model with concentrated plasticity links. The achieved results are focused on fundamental seismic performance issues of the upgraded structure, which are compared to the upgrading solution experimentally applied to the same case study.

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  • Special Issues

    • SEISMIC BEHAVIOUR OF SHEATHED CFS BUILDINGS: SHAKE TABLE TESTS AND NUMERICAL MODELLING

    Alessia Campiche, Sarmad Shakeel, Vincenzo Macillo, Maria Teresa Terracciano, Bianca Bucciero, Tatiana Pali, Luigi Fiorino, Raffaele Landolfo

    The objective of this paper is to describe the shake table tests and the numerical modelling of a cold-formed steel (CFS) building. The two-storey full scale building, named as ELISSA mock-up, was subjected to shake table tests at University of Naples “Federico II”, as a part of the European project Energy efficient LIghtweight- Sustainable-SAfe steel construction (ELISSA). The tests were performed at two phases of the building construction process. In the first phase, only structural part of mock-up was subjected to dynamic identification tests, while in the second phase, the architectonic nonstructural elements were added and the mock-up was tested under the action of natural earthquake input with the varying scaling factors. Test results showed that the investigated construction system has a good seismic performance, with very low inter-storey drifts and negligible damages. Moreover, the non-structural elements influenced greatly the seismic response of building. Furthermore, a numerical model was also developed for the experimental mock-up at both construction phases using the OpenSees software. Models were able to simulate with a good accuracy the nonlinear dynamic response of the whole building at both phases.

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  • Special Issues

    • SEISMIC PERFORMANCE OF DUAL STEEL FRAMES WITH DISSIPATIVE METAL SHEAR PANELS

    Gianfranco De Matteis, Giuseppe Brando, Federica Caldoso, Federica D’Agostino

    This paper deals with seismic response of dual steel frames with dissipative metal shear panels. The main goal is to provide design indications accounting for the main behavioural aspects of metal shear panels. To this purpose, numerical Incremental Dynamic Analyses (IDAs) using historical records have been carried out on two different steel frames, which have been properly designed in order to comply with specific design criteria. The outcomes highlight that metal shear panels allow a significant increment of collapse peak ground accelerations as well as a general reduction of both permanent and transient story drifts. The paper concludes with the evaluation of the equivalent q-behaviour factors to be used for simplified analysis. As it could be expected, a significant increment (up to 150%) have been determined in case of structures endowed with metal shear panels.

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  • Uncategorized

    • BEARABLE MAXIMUM SEISMIC ACTION FOR EXISTING CONCRETE DAMS BY ITALIAN STANDARD

    Martina Colombo, Marco Domaneschi, Aldo Ghisi, Stefano Griffini
    The recently updated Italian standard adds, to the conventional safety assessment, the evaluation of the bearable maximum seismic action for existing concrete dams. This prescription actually represents a trend of current International guidelines that are gradually replacing the previous, deterministic safe/fail rationale and are accounting for nonlinear behavior. Depending on dam typology, a preliminary evaluation of the maximum bearable seismic action can be interpreted as the research of a capacity function for a given failure mechanism. In this work, the bearable maximum seismic action is investigated through numerical, three-dimensional, finite element simulations via a multipurpose code for two existing concrete dams placed in a region of low-to-moderate seismicity. In the first case, an arch-gravity dam, the overcoming of the limit stress conditions in wide parts of the bulk, the stiffness degradation in the global nonlinear response, and the displacement discontinuity in structural joints are used for the evaluation. In the second case, for a buttress-gravity dam, the sliding in the construction and foundation is instead considered.

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