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Isolamento sismico a grande scala per la salvaguardia del tessuto urbano nella ricostruzione post-sisma
No full textAfter a seismic event, the observation of the consequences to buildings and infrastructures always highlights
extensive damage situations in old or historical district of the hit towns. Damage depends not only on the local
amplification of the seismic action, but also on the quality of the materials and the construction technique. The
negative consequences of traditional design and construction approaches appeared in all their negative evidence in
all areas of Central Italy affected by recent seismic sequences of medium intensity (M5-M6) in 2016-17. Now the
reconstruction should solve the problem to rebuild with safety but preserving the historical aspect of buildings and
landscape. This paper proposes a particular application of the known technique of seismic isolation for the integral
seismic protection of entire urban quarter or entire small centers characterized by building of different characteristics
also significantly irregular. The adoption of seismic isolation systems at village or quarter scale involves the
construction of large floating slabs, supported by seismic isolators and/or dampers, above which to construct
buildings that can present the aesthetic and constructive characteristics of the collapsed traditional ones. These large
slabs could have the size of entire compartments (hundreds of meters on each side). Solution of ground isolation have
already been implemented in various countries to isolate complex of buildings.
The solution allows a correct interpretation of the objective to rebuild "as it was, there where it was", safeguarding
the landscape, prolonging the lifetime, and saving the expected cost. The paper illustrates a case study related to a quarter of a historic town in central Italy and shows the constructive solutions
Analisi comparative per l'ottimizzazione di dispositivi di protezione sismica a basso costo per strutture prefabbricate.
No full textIl lavoro presenta gli sviluppi di una ricerca orientata allo studio di dispositivi di protezione sismica a basso costo
da inserire nell'ambito delle unioni di sistemi costruttivi in c.a. prefabbricati con l’obiettivo del miglioramento della
risposta sismica di tali sistemi costruttivi. Dopo un primo lavoro orientato allo studio di tecnologie disponibili sul
mercato si è proceduto all’analisi di un caso di studio e alla valutazione delle capacità prestazionali prima e dopo
l’inserimento dei dispositivi. In particolare questa fase della ricerca si è concentrata sull’ottimizzazione dei
dispositivi di protezione adottati. A tal fine, con riferimento ad un telaio piano della struttura caso di studio, si è
sviluppata un'analisi comparativa della risposta sismica del sistema al variare delle caratteristiche meccaniche del
dispositivo. Le prestazioni strutturali attese sono state controllate in termini di sollecitazioni nei pilastri e nelle
travi. I dispositivi di protezione adottati sono del tipo ad attrito e sono installati a cornice nell’interfaccia travepilastro
e pilastro-fondazione. Dalle analisi condotte si è evidenziato un miglioramento della risposta sismica, sia in
termini di riduzione delle sollecitazioni che della capacità dissipativa. E’ stata infine accertata anche la convenienza
economica dell’inserimento dei dispositivi nell’organismo strutturale
Impiego di dispositivi dissipativi per la riduzione della vulnerabilità di strutture prefabbricate.
No full textThe paper focuses on low-cost anti-seismic devices to be installed on precast buildings. The
behavior of 2D precast RC frames equipped with dissipative devices placed at beam-column joints
and at the columns base is studied. The research is aimed at optimize the mechanical parameters of
the devices and to estimate the effectiveness of their insertion at the column base too. The
performances before and after the insertion of the devices are compared also accounting for the
easiness of installation and costs reduction
SEISMIC PERFORMANCES OF A LARGE LIGHTLY-REINFORCED WALLS CONSTRUCTION SYSTEM WITH THERMAL INSULATING FORM-BLOCKS
No full texthis paper presents the main results of a study concerning the seismic behavior of building built with Large Lightly Reinforced Concrete Walls - Wood Blocks System (LLRCW - WBS). The building system has been character-ized from the structural point of view via experimental tests that demonstrate suitable behavior in the constituent ele-ments regarding vertical, horizontal and cyclic loads. The results obtained from experimental tests have been used to define the calculation models with the complete characteri-zation of the seismic capacity of the LLRCW–WBS building system
Seismic capacity of buildings made with reinforced concrete panels cast with wood blocks system.
No full textThis paper presents the main results of a nonlinear analysis used for the seismic design of a building
constructed with LLRCW - WBS panels (Large Lightly Reinforced Concrete Walls - Wood Blocks
System). The building system has been characterized from the structural point of view via
experimental tests that demonstrate suitable behavior in the constituent elements regarding vertical,
horizontal and cyclic loads . The results obtained from experimental tests have been used to define the
calculation models with the complete characterization of the seismic capacity of the LLRCW–WBS
building system. The results of the numerical analyses in terms of the mechanical behavior of the
panels, of their stress-strain states and of their global and local elastic-plastic behavior are then
described
Assessment and Seismic Improvement with Traditional and Innovative Technologies in the Reuse Design of San Benedetto Novello in Perugia
No full textThe paper deals with the design procedures for the refurbishment, seismic improvement and reuse of a class of historical buildings defined ordinary since they have an intermediate relevance within the cultural heritage of a country. The procedures include the basic knowledge, the assessment methods, the design works aimed at defining appropriate cost-effective technologies and methods for the structural and seismic retrofitting. The research is carried out with reference to an emblematic study-case concerning the reuse of the complex of San Benedetto Novello in Perugia as a center for artistic and cultural activities. The complex includes architectural elements attributed to Gaelazzo Alessi and is nowadays partially occupied by offices. The study provides for the evaluation of the structure safety considering both the global and local level with reference to the performance levels expected at the different limit states. The works for seismic improvement have been designed respecting the peculiarities of the ecclesiastical complex and allowing the performances required by the new functions. Special focus is given to the use of innovative restoring and strengthening technologies allowing for works characterized by cost effectiveness and contained invasiveness
Precast Industrial Buildings in Italy - Current Building Code and New Provisions Since the 2012 Earthquake.
No full textFirst of all the paper describes the Italian regulatory framework for precast buildings. Then the work focuses attention on the structural weaknesses most frequently found in existing precast buildings. It also discusses the changes made to building standards and to the technical specifications following the earthquake that struck the regions of Emilia-Romagna, Veneto and Lombardy in May 2012. Finally, it presents the guidelines developed by the Working Group on the Seismic Conformity of Industrial Buildings for the rapid restoration of accessibility and seismic improvement of existing precast buildings
Dissipative Devices for Vulnerability Reduction of Precast Buildings.
No full textThe paper presents the development of a study on low cost seismic protection devices to put in place at the joints of prefabricated structural systems with the aim of improving their seismic response. In particular, this phase of the research focuses on the optimisation of protection devices used on two-dimensional mono-and multi-storey frames. A comparative analysis of the seismic response of the systems varying the mechanical characteristics of the devices was developed. The friction-type protective devices adopted were installed at the beam-column and column-foundation interfaces. The performed analyses show a significant improvement in seismic response, in terms of both reduction of stresses and increase of dissipative capacity
Analysis of masonry structures strengthened with polymeric net reinforced cementitious matrix materials
No full textThe seismic rehabilitation techniques of masonry structures based on the use of plasters reinforced with
steel nets have been widely utilized in the last decades. More recently nets made of materials other than
steel have been used as plaster reinforcement, among them there are the polymeric nets. These nets
allow to overcome some of the limitations of the other strengthening materials and present a good
cost–benefit ratio. Experimental campaigns performed on masonry panels reinforced with polymeric nets
have allowed to define their mechanical properties for practical design applications and for assessing
their seismic capacity. Considering the results of these experimental campaigns in the present study analysis
methods of masonry structures made of masonry brick panels strengthened with plasters reinforced
with polymeric nets are proposed. The strength and ductility increments of the strengthened panels are
accounted for in the global analysis of the construction adopting suitable values of the behavior factor. In
the ambit of the limit analysis of the in plane and out of plane collapse mechanisms criteria that allow to
account for the contribution of the polymeric net in the containment of the evolution of these mechanisms
are defined
Vertical collapse mechanisms in masonry buildings due to seismic vertical component
No full textThe acceleration histories recorded in the epicentral areas during the last earthquake in Central
Italy (2016-17) show very intense vertical components. During the post-earthquake damage assessment operations
in the epicentral areas, some damage frameworks different from those described in the literature have
been observed, with a macro-element collapse mode attributable to the action of the earthquake vertical component.
The paper presents some of these buildings characterized by the presence of horizontal cracks, by the
displacement of the highest levels, by vertical cracks in the sub-window walls. The masonry walls are undamaged
without the typical shear or flexure failure cracks and the lower levels do not show any damage. The
crack pattern and the associated collapse mechanisms cannot be included within the classic in-plane and outof-
plane mechanisms. A collapse mechanism characterized by the loss of vertical connection of entire structural
bodies is therefore hypothesized. The activation of this type of mechanism would seem to exclude the
formation of the classic collapse mechanisms on which the seismic capacity checks of the masonry structures
provided by the technical codes are based. A simplified linear kinematic analysis able to analyze the described
behavior is proposed and illustratively applied to a case study building. Criteria for the identification and verification
of the proposed mechanisms are described, with the aim to introduce the method in design codes
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