No abstract

The seismic events that struck the Italian region Emilia-Romagna in 2012 provoked not only numerous injuries and casualties but also vast damage to thousands of buildings, infrastructures, and production sites. In particular, unlike other Italian sequences, that of 2012 was notable for the high value of losses in the industrial sector. Soon after the earthquakes, plans were set up in order to provide financial help to both citizens and enterprises, and to this aim the regional authority gathered and classified damage and loss reports. Information was collected in a database called SFINGE. This study is an empirical data analysis of a consistent subset of SFINGE, whose elements are long-span-beam buildings used as production sites. Results are in terms of direct economic losses and cost of reconstruction. This work is a precious source of seismic economic consequence assessment tools for the considered building typology, within the framework of Performance-Based Earthquake Engineering.

The 2012 Emilia-Romagna earthquake, that mainly struck the homonymous Italian region provoking 28 casualties and damage to thousands of structures and infrastructures, is an exceptional source of information to question, investigate, and challenge the validity of seismic fragility functions and loss curves from an empirical standpoint. Among the most recent seismic events taking place in Europe, that of Emilia-Romagna is quite likely one of the best documented, not only in terms of experienced damages, but also for what concerns occurred losses and necessary reconstruction costs. In fact, in order to manage the compensations in a fair way both to citizens and business owners, soon after the seismic sequence, the regional administrative authority started (1) collecting damage and consequence-related data, (2) evaluating information sources and (3) taking care of the crosschecking of various reports. A specific database-so-called Sistema Informativo Gestione Europa (SFINGE)-was devoted to damaged business activities. As a result, 7 years after the seismic events, scientists can rely on a one-of-a-kind, vast and consistent database, containing information about (among other things): (1) buildings' location and dimensions, (2) occurred structural damages, (3) experienced direct economic losses and (4) related reconstruction costs. The present work is focused on a specific data subset of SFINGE, whose elements are Long-Span-Beam buildings (mostly precast) deployed for business activities in industry, trade or agriculture. With the available set of data, empirical fragility functions, cost and loss ratio curves are elaborated, that may be included within existing Performance Based Earthquake Engineering assessment toolkits.

According to EN 1998‐4:2006 3.4 (4), elevated silos may be designed considering medium or high ductility class for the support structure, abbreviated DCM and DCH respectively, for which an overall behaviour factor q greater than 1,5 may be assumed. Undoubtedly, when a silo or tank supported by a sway frame or a vessel with integrated legs is considered, it is expected that plasticity will be induced due to the overall system's performance and thus, motion amplitudes will be reduced due to energy dissipation. However, the shell upper‐structure is a very thin‐walled class 4 cross section. Hence, it might fail due to buckling at much smaller motion amplitudes (corresponding to acceleration amplitudes) than those, which the support structure can follow without failing. Therefore, from the authors' point of view it is not sufficient to settle with a single behaviour factor for the overall structural system. Alternatively, a two‐step approach is recommended: With this two‐step approach it can be verified, that (sudden) buckling of the shell does not happen prior to the introduction of plasticity at the sub‐structure and in extension to the desired energy dissipation. The proposed two‐step approach is demonstrated by suitable examples with a different range of parameters. Therewith, it will be shown that the assumption of q = 1,5 for elevated silos or tanks can be unsafe. An improvement of the current EC8‐4 rules is proposed in order to enable a practical, safer and more efficient design procedure.

Summary A refined substructure technique in the frequency domain is developed, which permits consideration of the interaction effects among adjacent containers through the supporting deformable soil medium. The tank‐liquid systems are represented by means of mechanical models, whereas discrete springs and dashpots stand for the soil beneath the foundations. The proposed model is employed to assess the responses of adjacent circular, cylindrical tanks for harmonic and seismic excitations over wide range of tank proportions and soil conditions. The influence of the number, spatial arrangement of the containers and their distance on the overall system's behavior is addressed. The results indicate that the cross‐interaction effects can substantially alter the impulsive components of response of each individual element in a tank farm. The degree of this impact is primarily controlled by the tank proportions and the proximity of the predominant natural frequencies of the shell‐liquid‐soil systems and the input seismic motion. The group effects should be not a priori disregarded, unless the tanks are founded on shallow soil deposit overlying very stiff material or bedrock. Copyright © 2016 John Wiley & Sons, Ltd.