Base Isolation for Seismic Retrofitting of a Multiple Building Structure: Evaluation of Equivalent Linearization Method

Although the most commonly used isolation systems exhibit nonlinear inelastic behaviour, the equivalent linear elastic analysis is commonly used in the design and assessment of seismic-isolated structures. The paper investigates if the linear elastic model is suitable for the analysis of a seismically isolated multiple building structure. To this aim, its computed responses were compared with those calculated by nonlinear dynamic analysis. A common base isolation plane connects the isolation bearings supporting the adjacent structures. In this situation, the conventional equivalent linear elastic analysis may have some problems of accuracy because this method is calibrated on single base-isolated structures. Moreover, the torsional characteristics of the combined system are significantly different from those of separate isolated buildings. A number of numerical simulations and parametric studies under earthquake excitations were performed. The accuracy of the dynamic response obtained by the equivalent linear elastic model was calculated by the magnitude of the error with respect to the corresponding response considering the nonlinear behaviour of the isolation system. The maximum displacements at the isolation level, the maximum interstorey drifts, and the peak absolute acceleration were selected as the most important response measures. The influence of mass eccentricity, torsion, and high-modes effects was finally investigated

Analysis of Fluid-structure Interaction for a Submerged Floating Tunnel

Abstract The behavior of a submerged floating tunnel (SFT) exposed to a water current of variable velocity is investigated through complex numerical analyses based on the Computational Fluid Dynamics (CFD) and the Finite Element Method (FEM) implemented in the ABAQUS code. An accurate modelling of turbulent phenomena is made, based on both Implicit Large Eddy Simulation and the RANS-based Spalart-Allmaras model, followed by a co-simulation procedure in which the fluid dynamics and the structural analysis are carried out separately and interfaced with each other. Circular and elliptical cross sections are considered, each of them fitted for combined railway and motorway services. The analysis is carried out in both static and dynamic way, by varying the current velocity with a given value of the residual buoyancy of the tunnel. The results emphasize the effect of the main parameters investigated, evidencing the great potentials of the adopted calculation tool for carrying out further investigations aimed at achieving useful elements for the design and optimization of the SFT

Seismic and Robustness Design of Steel Frame Buildings

In this paper, a design procedure that combines both progressive collapse design under column removal scenario and capacity design to produce a hierarchy of design strengths is presented. The procedure develops in the context of the European Standards, using the classification of European steel sections and considering the seismic design features. Three-dimensional models of typical multi-storey steel frame buildings are employed in numerical analysis. The design for progressive collapse is carried out with three types of analysis, namely linear static, nonlinear static and nonlinear dynamic. Since the behaviour following sudden column loss is likely to be inelastic and possibly implicate catenary effects, both geometric and material nonlinearities are considered. The influence of the fundamental parameters involved in seismic and robustness design is finally investigated

The EC 9 Design Provisions for Aluminium Shells: Background and Development.

The new Part 1-5 of Eurocode 9, shaped within the activity of CEN/TC 250/SC9 Committee chaired by F.M. Mazzolani, is the very first issue specifically devoted to shell structures made of aluminium alloys in the field of European codification. Because of this, the new document marks a major advance in the codification on shells for ...

Assessment of progressive collapse-resisting capacity of steel moment frames

"In this study the progressive collapse-resisting capacities of steel moment-resisting frame. buildings designed according to the Italian Code were evaluated. At first, a stepwise increment of amplified. vertical loads (pushdown analysis) for a variety of possible scenarios regarding the location of the. missing column was employed. Then, as the nonlinear dynamic analysis for progressive collapse analysis. does not require modeling of complicated hysteretic behavior and may be used as a practical tool, it. was applied for evaluation of progressive collapse potential with the same first story column suddenly. removed. According to the analysis results, the progressive collapse potential varied significantly depending. on the location of the removed column. It was also observed that the pushdown analysis may greatly. overestimate the inelastic response of the structure.

Base Isolation for Seismic Retrofitting of a Multiple Building Structure: Design, Construction, and Assessment

The paper deals with the seismic retrofit of a multiple building structure belonging to the Hospital Centre of Avellino (Italy). At first, the paper presents the preliminary investigations, the in situ measurements and laboratory tests, and the seismic assessment of the existing fixed-base structures. Having studied different strategies, base isolation proved to be the more appropriate, also for the possibility offered by the geometry of the building to easily create an isolation interface at the ground level. The paper presents the design project, the construction process, and the details of the isolation intervention. Some specific issues of base isolation for seismic retrofitting of multiple building structures were lightened. Finally, the seismic assessment of the base-isolated building was carried out. The seismic response was evaluated through nonlinear time-history analysis, using the well-known Bouc-Wen model as the constitutive law of the isolation bearings. For reliable dynamic analyses, a suite of natural accelerograms compatible with acceleration spectra of Italian Code was first selected and then applied along both horizontal directions. The results were finally used to address some of the critical issues of the seismic response of the base-isolated multiple building structure: accidental torsional effects and potential poundings during strong earthquakes

La seconda generazione dell’Eurocodice 9 (EN 1999 - “Aluminium Structures”)

Unico ad aver ricevuto il voto formale all’unanimità già a dicembre 2022, l'Eurocodice 9 di seconda generazione, dedicato alla progettazione delle strutture in alluminio porta con se alcune novità tra cui la riduzione del numero di parametri determinati a livello nazionale (NDP), l'introduzione di ulteriori tipologie strutturali (ponti, coperture, sistemi composti alluminio-calcestruzzo), nuove tipologie di connessione e altre ancora. Ce ne parlano Federico M. Mazzolani, Former Chair of CEN/TC 250/SC9 e Alberto Mandara – Chair of CEN/TC 250/SC9