Robustness of Industrial Precast Buildings due to Damage Accumulation

La robustezza degli edifici industriali, definita come la capacità della struttura di resistere ad azioni eccezionali come eventi sismici evitando un collasso globale, è uno dei principali argomenti di ricerca a causa della grave perdita umana ed economica che causa la mancanza di tale caratteristica. La maggior parte degli edifici industriali esistenti sono stati realizzati con normative senza specifici standard per strutture prefabbricate in cui la progettazione degli elementi costruttivi si basava sulle singole soluzioni progettuali dei produttori. Le strutture industriali prefabbricate italiane esistenti a grandi luci possono essere suddivise in due categorie principali a seconda dell'evoluzione delle tecniche di prefabbricazione. La prima categoria si sviluppa dai primi anni trenta fino alla metà degli anni sessanta con strutture industriali in c.a. gettate in opera con un uso diffuso di volte leggere prefabbricate per coprire ampie luci, mentre la seconda è prodotta a partire dagli anni cinquanta tutt’ora in uso riguardante la tipica struttura a telaio prefabbricato con tutti gli elementi realizzati in stabilimento ed assemblati sul posto. Nelle prime tipologie di edifici industriali, la robustezza è definita considerando diversi stati limite di deformabilità e resistenza di pilastri e travi combinati con la vulnerabilità specifica del sistema voltato prefabbricato, sapendo che la struttura è soggetta ad una combinazione di eventi sismici ravvicinati nel tempo che portano all'accumulo del danno. Nel secondo caso la robustezza della struttura del telaio prefabbricato è solitamente basata sulle connessioni di elementi strutturali e non (pannelli di tamponamento) e nell'attivazione dell'effetto domino passando dal collasso di tipo locale a quello globale. In questo lavoro sono analizzati diversi modelli ad elementi finiti per rappresentare al meglio il comportamento strutturale lineare e non lineare di entrambi i tipi di strutture prefabbricate considerate.Robustness of industrial buildings, defined as the capacity of the structure to withstand exceptional actions like seismic events avoiding a global collapse, is one of the main topics of research due to the serious human and economic loss that the lack of such feature could cause. Most of the existing industrial buildings are made with precast elements realised with low-code without specific detailed standards for precast structures in which the technical achievement of them relies on the individual producers with their design solutions. Existing Italian precast structures for large-scale industrial buildings can be divided into two main categories depending on the evolution of prefabrication techniques. The first category was developed from the early thirties up to the mid-sixties, with RC industrial structures cast in place with a widespread use of precast vault to cover a large span, while the second one started to be produced at the beginning of the fifties and is still in use as regards the typical precast frame structure with all its main elements made in factory and assembled in place. In the first type of industrial buildings, only the roof is precast and usually made in reinforced hollow brick light-weight vault and the robustness is defined considering several limit states of chord-rotation and shear capacity of columns and main beams combined with specific vulnerabilities of the precast vault, considering that every seismic sequence is usually a combination of a mainshock and several aftershocks which lead to the damage accumulation on the structure. In the second case the robustness of precast frame structures is usually based on the connections of structural and non-structural elements (cladding panels) and on the activation of the domino effect passing from local to global collapse. In this work several finite element models to best represent the linear and nonlinear structural behaviour of both types of precast structures considered are analysed

Aftershock fragility assessment of Italian cast–IN–place RC industrial structures with precast vaults

Through a fragility analysis carried out with different probabilistic methods, the vulnerability of an Italian cast-in-place RC industrial structure with precast reinforced hollow brick light-weight vaults is evaluated via nonlinear analyses. After a brief description of the vault construction system, a typical case study built in the 1960s is considered and the influence of FE numerical modelling through three different representations of the vault system is assessed. Fragility curves are calculated by Incremental Dynamic Analysis (IDA), with three damage limit threshold values corresponding to local limit conditions regarding bending or shear that first occur in a few elements, as determined through pushover analyses. A comparison of fragility curves in the two horizontal directions (X–Y) for the three models is reported. Concerning the model with the greatest probability of collapse, seismic sequence effects on structural damage with the same ground motions for mainshock and aftershock are taken into account. Double Incremental Dynamic Analysis (D-IDA), with the mainshock represented by several fixed percentages of Near Collapse PGAs previously evaluated in X–Y directions and scaled aftershocks, is performed and compared to the IDA results. Aftershock fragility curves created with only the damage limit threshold value of Near Collapse are likened to the case that analyses a single seismic event (undamaged structure). Furthermore, ductility damage indices are calculated for maximum displacements obtained by each nonlinear dynamic analysis of IDA and D-IDA

The non-smooth contact dynamics method for the analysis of an ancient masonry tower

The dynamics of a medieval tower, inside the Basilica of San Benedetto in Ferrara (Italy), subjected to transversal dynamic loadings has been analyzed by using a distinct element code which implements the Non-Smooth Contact dynamics method. Since the contact between blocks is governed by the Signorini's impenetrability condition and the dry-friction Coulomb's law, the tower exhibits discontinuous dynamics. The sliding motions of blocks are non-smooth functions of time. Numerical simulations are performed with the aim of investigating the influence of the friction coefficient but also of the amplitude and frequency of the excitation at the base

Modelling and analysis of an ancient monastery under earthquake loading: assessment of seismic resistance

The paper discusses the static behaviour and the seismic vulnerability of a historical building, in particular a monastery currently used as a Regional Headquarter of the Marche Region by the Italian Army. The building is located in Ancona, a site characterized with a medium-high seismic risk. Monasteries, as churches, represent a large portion of the Italian (and European) cultural heritage particularly susceptible to damage and prone to partial or total collapse under earthquake loads; for these reasons they are of economic and engineering concern. The high seismic vulnerability of this type of buildings is due to both the specific mechanical properties of masonry materials (characterized by a very small tensile strength) and the particular configuration of the buildings itself, which are characterized by an open plan layout often with perimeter slender walls. Moreover the vulnerability of these historical masonry buildings is enhanced by the absence of adequate connections between the various parts constituting the structural complex and by the presence of thrusting horizontal structures (triumphal arches, etc.) as already discussed in several studies [1,2]. Furthermore, it is no longer used as a monastery, a fact that changes the hazard aspects [3]. A finite element methodology for the static and dynamic analysis of historical masonry structures is described and applied to the case study. In particular 3D linear and nonlinear analyses (which take into account the nonlinear behaviour of masonry) are performed. Also constitutive assumptions, characterized by elasticity, damage and friction, are done. The behaviour of the masonry is simulated by use of solid elements which can have their stiffness modified by the development of cracking and crushing. The comparison demand vs. capacity confirms the susceptibility of this type of buildings to extensive damage and possibly to collapse. At the end, we have conducted some analyses of active failure mechanisms in the light of the observed state of damage and of the FEM results

Seismic Assessment of a Monumental Building through Nonlinear Analyses of a 3D Solid Model

The paper analyzes the static behavior and the seismic vulnerability of the “San Francesco ad Alto” building in Ancona (Italy), which is currently used as a Regional Headquarter of the Marche Region by the Italian Army and was formerly a monastery. The global static structural behavior and the dynamic properties have been evaluated using the Finite Element modeling technique, in which the nonlinear behavior of masonry has been taken into account by proper constitutive laws. The concepts of homogenized material and smeared cracking are used to evaluate the capacity of the monastery to withstand lateral loads together with the expected demands resulting from seismic actions (N2 method), using a nonlinear static analysis (pushover). The comparison of seismic demand and capacity confirms the susceptibility of these types of buildings to extensive damage and collapse, as frequently observed in similar buildings. This paper aims to point out that advanced numerical analyses can offer significant information on the understanding of the actual structural behavior of historical buildings. It is believed that the methodology and the overall conclusions of this case study are valid for many historical monasteries in Europe

Monitoring cultural heritage buildings: The San Ciriaco bell-tower in Ancona

The preliminary results of an ambient-vibration based investigation conducted on the San Ciriaco Belfry in Ancona (Italy) is presented. The assessment procedure includes full-scale ambient vibration testing, modal identification from ambient vibration responses, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. As the most doubtful parameters, the modulus of elasticity of the masonry is adjusted to achieve the experimental results with numerical model by simple operation