Month: April 2016

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    • PREFACE

    Dear Readers,

    this special issue comprises selected papers presented at the XXV edition of“Italian Steel Days” held in Salerno on October 1-2, 2015. This conference represents the place where Italian researchers present their results and development activities in the field of Steel Structures. Common papers’ emphasis is about the structural performance under seismic conditions. Due to the number of selected papers, in addition to the current issue, a second one is in preparation. The Guest Editors, Rosario Montuori and Francesco Fabbrocino, wishes to thank Dr. Gianmario Benzoni for this opportunity and for his assistance.

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    • SIMPLIFIED NUMERICAL MODELING OF ELEVATED SILOS FOR NONLINEAR DYNAMIC ANALYSIS

    Carlo Andrea Castiglioni, Alper Kanyilmaz

    Silos are industrial facilities used for storing a huge range of different materials. They should be designed to resist several loading conditions, and their seismic behaviour strongly depends on the geometrical and mechanical behaviour of their supporting frame, and the nonlinear behaviour of the content (e.g. friction, content-silo wall interaction). Nonlinear dynamic simulation of such systems can be very time-consuming, and most of the time unfeasible. This study compares a finite element model made of bricks elements and a simpler model with distributed masses on the silo walls. While simplified models were not suitable to simulate local behaviour of the silo wall, they reasonably predicted the global response of the elevated silo system. Yet, the accuracy strongly depended on the rigidity of the supporting structure, and this should be investigated carefully during the calibration phase.

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    • FULL AND PERFORATED METAL PLATE SHEAR WALLS AS BRACING SYSTEMS FOR SEISMIC UPGRADING OF EXISTING RC BUILDINGS

    Antonio Formisano, Luca Lombardi, Federico M. Mazzolani

    Metal Plate Shear Walls (MPSWs) represent an effective, practical and economical system for the seismic protection of existing RC framed buildings. They consist of one or more metallic thin plates, bolted or welded to a stiff steel frame, which are installed in the bays of RC framed structures. A case study of an existing RC residential 5-storey building, designed between the ‘60s and ‘70s of the last century and retrofitted with MPSWs, has been examined in this paper. The retrofitting design of the existing structure has been carried out by using four different MPSWs, namely three common full panels made of steel, low yield steel and aluminium and one innovative perforated steel plates. Finally, the used retrofitting solutions have been compared each to other in terms of performance and economic parameters, allowing to select the best intervention.

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    • FEM SIMULATIONS OF A NEW HYSTERETIC DAMPER: THE DISSIPATIVE COLUMN

    Paolo Castaldo, Bruno Palazzo, Francesco Perri

    A new replaceable hysteretic damper to better control seismic building damage, consisting of two adjacent steel vertical elements connected to each other with continuous X-shaped mild/low strength steel shear links, is investigated in this study. New Dampers, called Dissipative Columns (DC), provide additional stiffness and damping to a lateral system by using a basic and minimally invasive construction element: the column. The Dissipative Column has been conceived or as a device installed within a frame either external damper to provide macro-dissipation. In fact, considering different configurations, a parametric analysis, based on FEM simulations, is developed in order to evaluate the effect of the main geometrical and structural parameters as well as provide the design capacity curves of this new damper. In particular, non-linear pushover and cyclic analyses have been carried out in ABAQUS in order to characterize the local and global behaviour of the device also considering different steel grades. 

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    • AN ADAPTIVE CAPACITY SPECTRUM METHOD FOR ESTIMATING SEISMIC RESPONSE OF STEEL MOMENT-RESISTING FRAMES

    Massimiliano Ferraioli, Angelo Lavino, Alberto Mandara

    An adaptive version of the capacity spectrum method is proposed to estimate deformation demands of steel moment-resisting frames under seismic loads. Its computational attractiveness and capability of providing satisfactory predictions of seismic demands in comparison with those obtained by other advanced nonlinear static procedures in literature are examined. Both effectiveness and accuracy of these approximated methods based on pushover analysis are verified through an extensive comparative study involving both regular and irregular steel moment-resisting frames. The results obtained by nonlinear static procedures and nonlinear dynamic time-history analysis under spectrum-compatible accelerograms are eventually compared. The proposed procedure generally gives a more accurate solution than that obtained from the other nonlinear static procedures.

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    • Seismic Application of Pentamode Lattices

    Francesco Fabbrocino, Ada Amendola, Gianmario Benzoni, Fernando Fraternali

    The category of “extremal materials” has been introduced in the literature to define materials that simultaneously show very soft and very stiff deformation modes (unimode, bimode, trimode, quadramode and pentamode materials, depending on the number of soft modes). This definition applies to a special class of mechanical metamaterials – composite materials, structural foams, cellular materials, etc. – which feature special mechanical properties. Pentamode materials have been proposed for transformation acoustics and elasto-mechanical cloak, but their potential in different engineering fields is still only partially explored. We here present novel versions of pentamode materials: artificial structural crystals showing shear moduli markedly smaller than the bulk modulus. Novel pentamode lattices with tensegrity architecture are designed, through the insertion of actuated struts and/or prestressed cables within basic pentamode lattices. Such systems are proposed as tunable seismic base-isolation devices, profiting from their low and adjustable shear moduli, which can be easily adapted to the dynamic properties of the structure to be isolated.

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    • CRITICAL REVIEW OF SEISMIC DESIGN CRITERIA FOR CHEVRON CONCENTRICALLY BRACED FRAMES: THE ROLE OF THE BRACE-INTERCEPTED BEAM

    Silvia Costanzo, Mario D’Aniello, Raffaele Landolfo

    Steel chevron concentrically braced frames are expected to dissipate seismic energy by yielding of the brace under tension, while both beam and columns behave elastically. Besides the strength, also the stiffness of the brace-intercepted beam plays a key role to avoid unfavourable mechanisms. However, no codified requirements are provided to assure adequate beam rigidity. In order to examine this aspect, in the first part of this paper the main results of a numerical parametric study devoted to investigate the mutual interaction between the beam vertical deflection and the brace ductility demand are described. The second part of this article investigates the efficiency of both EC8 and AISC341-10 seismic provisions on the global performance of chevron bracings, particularly focusing on the design of the beam of the braced bays. The results of incremental dynamic analyses performed on several structures confirm the primary importance of the flexural stiffness of the beam.

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    • INFLUENCE OF THE CYCLIC BEHAVIOUR OF BEAM-TO-COLUMN CONNECTION ON THE SEISMIC RESPONSE OF REGULAR STEEL FRAMES

    Rosario Montuori, Elide Nastri, Vincenzo Piluso, Marina Troisi

    The work presented is aimed at the investigation of the influence of beam-to-column connection typologies on the seismic response of MR-Frames designed according to the Theory of Plastic Mechanism Control (TPMC). The investigated typologies are four partial strength connections designed in order to obtain the same flexural resistance. The first three joints are partial-strength semi-rigid connections while the fourth one is a beam-to-column connection equipped with friction pads properly designed to assure the earthquake input energy dissipation. Beam-to-column joints are modelled by means of rotational inelastic spring elements located at the ends of the beams whose moment-rotation curve is characterized by a cyclic behaviour accounting for stiffness and strength degradation and pinching phenomenon. The parameters characterizing the joints cyclic hysteretic behaviour have been calibrated on the base of experimental results aiming to the best fitting. The prediction of the structural response has been carried out by means of IDA analyses.