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This paper presents the results of experimental tests on reduced-scale models of multistory masonry buildings with rigid floors. The laboratory investigation includes pushover tests of the aforementioned buildings and quasi-static, monotonic and cyclic tests of basic elements (panels and columns) of common masonry structures. Such tests highlight a noticeable inelastic behavior of the masonry and, consequently, an appreciable ductility of the models. The presented laboratory experimentation does not allow an immediate extension of the experimental results to the behavior of actual structures, but it qualitatively highlights the investigated phenomenon. Furthermore, it allows the verification of the reliability of the numerical results provided by the non-linear theoretical models developed by researchers in recent years

In the current paper, the experimental investigation of an innovative solution based on the use of slender steel shear panels for seismic upgrading of existing reinforced concrete frames is presented. Based on a preliminary experimental evaluation of the performance of the bare r.c. structure, an ad hoc design procedure has been developed in the framework of the performance based design methodology. Therefore, the steel panel configuration arrangement has been defined according to a simplified analytical procedure and then checked by adopting a sophisticated FEM model. Finally, after the global numerical analyses of the whole system, the full-scale test of the upgraded structure has been carried out, confirming the effectiveness of the adopted retrofitting device.

This paper deals with a critical analysis of the current seismic design criteria provided by Eurocode 8 for Moment Resisting Frames. This approach is based on the capacity design principle, in which the design is governed by the strength and stability of the structural elements and by hierarchy ofstrength, this in order to allows development of high dissipative collapse mechanism. The drawbacks of this approach is that the maximum required inter-storey drifts, at service limit states, are not directly satisfied. This leads to an enlargement of geometrical dimensions of the elements, producing significant over-strength and nullifying the use of high behaviour factors. In this paper, an alternative design criterion is proposed. According to this the design is governed by maximum inter-storey drift at service limit state, whereas the satisfaction of capacity design rules is contextually verified. This means to design the structure with seismic actions corresponding toservice earthquakes (i.e. unitary q-factor). Linear and non-linear static analyses on 3, 6 and 9-storey steel frames were performed to compare the design methodologies in terms of push-over curves (i.e.over-strength), interstorey- drifts and collapse mechanisms. Furthermore, the effect of panel zone on the global seismic response of frames was taken into accountin the performed analyses. It has been properly modelled using one of the most diffused literature model, the so called Krawinkler's 'frame model', accounting both its elastic and plastic behaviour.

This paper investigates the role of the horizontal axial force on the in-plane shear and flexural strength of masonry spandrels subjected to seismic actions. Strength criteria included in the main national and international codes take into account for geometrical and material properties, but valuable considerations about the influence of the horizontal axial force are missing. Nevertheless, experimental programs and post-earthquake damage scenarios proved that the horizontal axial force within the spandrels can be also significant under seismic actions, especially when they are surrounded by strength and stiff vertical piers or when significantly compressed by the effect of tensile-resistant elements. As main purpose, the strength criteria proposed by the Italian code for the spandrels have been revised accounting for the effect of the horizontal axial force on its shear and flexural strength. A database containing experimental tests conducted on masonry spandrels was elaborated and used to compare experimental with theoretical results. Outcomes showed that the revised criteria match satisfactorily the experimental results when significant axial forces affect the spandrels, both in terms of strength and failure mechanism. Contrariwise, existing code formulations are representative for the spandrels subjected to low axial force such that rocking or pure shear mechanisms tend to prevail.

Seismic capacity assessment of existing buildings is of paramount importance for mitigating the seismic risk in earthquake-prone areas. In Europe, the next version of Eurocode 8 and the current version of the Italian standards suggest the adoption of both linear and nonlinear approaches to perform seismic analyses of existing masonry buildings. This paper discusses with the main issues concerning linear and nonlinear analyses methodologies provided by the Italian standards for existing unreinforced masonry buildings. An historical building located in Southern Italy, representative of the Mediterranean basin buildings, has been chosen as a case study and modelled through the equivalent frame model. According to the Italian standards, the influence of in-plane stiffness of floors and spandrels on the overall seismic capacity of the structure has been considered in the analyses. Beyond the code prescriptions, the effect of different ultimate drifts values assumed for the spandrels on nonlinear behavior of the structure has been analysed. The results of two types of linear analyses (lateral static force method and modal response spectrum analysis) have been compared among them and with those provided by the nonlinear static method. Conclusions show that either behavior and overstrength factors provided by the Italian standards are conservative than those estimated through the nonlinear static analyses. Moreover, it has been remarked that the value of ultimate drift adopted for the spandrel can affect significantly the nonlinear response of the structures, although this topic still represents an open issue.

In 2007 the Italian National Research Council published the technical document CNR-DT 206/2007 “Instructions for the design, execution and control of timber structures”, with the purpose to provide a technical support to the operators of the sector, in line with the most advanced knowledge at that time. Since then, the world of timber engineering has largely used such document, even though the instructions are not mandatory standard rules, so that they became the most common tool in Italy for the structural use of timber, opening the markets and favouring competition and new applications. In latest years new studies, researches and innovative proposals have promoted the development and the growth of timber constructions also in the civil residential field. The framework of standard rules for constructions and products, both Europeans and Italians, has evolved too. For these reasons, CNR has considered as opportune to proceed to the editing of a new version, updated and widened, namely with the acronym DT 206-R1. The document comes from the spontaneous cooperation of an open group of specialists and operators of the sector, based on a wide discussion on the common scientific and technical expertise and knowledge. The current version has already taken into account the results of the public inquiry phase (concluded by now). The paper presents the main contents of the document, evidencing the innovations.

This paper provides a comphrensive review of the critical aspects of nonlinear modeling for evaluating the seismic response of masonry structures, emphasizing the issues relevant to engineering practice. Currently, the specialized technical community shares the opinion that, for a performance-based approach, numerical models are the only tools sufficiently effective to support the seismic assessment of existing buildings. However, their potential often falls short when attempting to accurately describe the behavior of masonry structures. In fact, these structures feature highly complex architectural configurations, different masonry types, and various structural solutions, meaning that extra care is required in numerical modeling. This is especially true when the modelers do not have a solid background in the software chosen and may not be practiced using the vast variety of options offered by the software houses. They are often unaware of the consequences that questionable modeling choices may have on the results obtained by the models. These extremely complex topics are treated in the paper from an engineering practice perspective, providing an in-depth overview of the challenging issues related to the use of different modeling strategies. The paper covers strategies ranging from the Equivalent Frame approach (widelyused in common engineering practice) to more refined techniques like 2D and 3D FiniteElement procedures based on continuous, discrete, and micro-mechanical approaches. Critical aspects in the modeling of both in- and out-of-plane responses of masonry, as well as the critical issues in wall-to-wall connections and diaphragm roles are investigated. All the examined issues are clarified through numerical examples highlighting also how a consistent and integrated use of different procedures may be beneficial. Finally, some of most relevant challenging issues concerning the use of numerical models in seismic assessment with the nonlinear static approach are presented and discussed.

This paper presents a novel hybrid-based methodology devoted to develop urban fragility curves and damage probability matrices to predict likelihood seismic damage scenarios for small and medium Italian urban centres, considering URM buildings only. The concept of urban fragility curve consists of a single curve mean-representative of the seismic fragility of an entire area accounting for the combinations of building classes and their percentage, then they differ from those typological. The methodology has been developed with reference to Rocca di Mezzo, a small Italian urban centre located in the central Apennine area, Italy. Based on CarTiS inventory, building classes have been firstly recognized and urban fragility curves, representative for damage scenarios at Ultimate Limit State, developed. To predict damage scenarios from low to high-intensity earthquakes, an approach to define multi-damage urban fragility curves and damage probability matrices has been also presented. To this aim, a damage scale suffered by building classes has been defined by converting the final outcomes of the AeDES form (used in Italy for post-earthquake surveys) in the damage levels provided by the European Macroseismic Scale (EMS98). Data coming from urban fragility curves have been compared with the actual damage scenario recorded in Rocca di Mezzo after the 2009 L’Aquila’s earthquake, in terms of both peak-ground acceleration and Mecalli-Cancani-Sieberg scale. The achieved results showed a good accordance between theoretical predictions and actual damage scenarios, coherent also with the damage scenarios occurred in other Italian historical centres hit by severe earthquakes over the years. Thus, the methodology can provide a first important indicator to support the development of emergently plans devoted to identify priority of interventions in such areas particularly vulnerable with respect to others.

This paper investigates the potentials of inter-story isolation systems (IIS) for retrofitting irregular masonry buildings by means of an isolated vertical addition realised on the roof of the existing structure. By assuming a case study, a wide parametric analysis is firstly carried out on lumped-masses model for identifying the dynamic properties of the isolated superstructure that minimizes the global seismic response. Hence, a 3D FE model is adopted for the detailed design and analysis of the IIS structure, with different solutions, in order to regularize the global seismic response of the IIS complex. Finally, some general design criteria are suggested.

Unreinforced masonry is the most diffused construction material in the major part of historical centers in Europe. In a building subjected to earthquake forces the contribution of in-plane shear resistance of the masonry walls is a determinant factor for the stability of the whole structure. In particular, the masonry piers are the structural elements subjected to the combination of normal and shear forces. In general, ductile tools to model the in plane behaviour of masonry are always welcome in order to evaluate the capacity of walls subjected to vertical and horizontal actions. In this framework, two no-tension approaches to model the behaviour of masonry walls loaded with in-plane forces, involving a minimum energy procedure, are presented. Both the procedures allow the representation of the stress maps in the panel in case of monotonic increase of shear load. The results of the numerical analyses are compared and discussed., Frattura ed Integrità Strutturale, 14 (51)

This paper presents the results of an experimental program conducted on H-shaped reduced-scale reinforced masonry spandrels subjected to monotonic loadings. It summarized tests units, test set-up and experimental results relative to seventeen samples reinforced by thin-steel stripes arranged with different configurations, and compared with those unreinforced. The first configuration comprised masonry spandrels strengthened by unbonded horizontal and diagonal steel stripes (i.e., stripes connected by means of threaded rods to the nodal area of the panel), while the second masonry spandrels reinforced by bonded horizontal stripes (i.e., stripes connected with 5 or 13 threaded rods over the spandrel length). For each reinforcement configuration, slender, intermediate and squat slenderness ratios have been considered for the samples. The conducted research investigated the effectiveness of the reinforcement to enhance the seismic response of the spandrels. Test results demonstrated that the application of steel stripes is beneficial in changing the failure modes from shear-dominated into flexural-dominated, especially for intermediate and squat panels prone to brittle shear mechanisms. Despite that increases of strength are reduced with respect to unreinforced samples, when reinforced the post-peak response changes significantly being it characterized by a remarkable ductile response for whatever spandrels’ slenderness ratios.

Typically, panel-to-panel and panel-to-foundation connection zones in Cross-Laminated Timber (CLT) walls consist of steel-to-timber mechanical connections (hold-downs and angle-brackets) and timber-to-timber contact. While hold-downs and angle brackets are extensively studied in literature, the role of timber-to timber contact is underestimated. The platform constructional technology used for build CLT walls requires that the vertical timber panels compresses the horizontal CLT floors, engaging the orthogonal to grain timber properties in the seismic response. This paper discusses a new development concerning a theoretical sectional model for CLT panels proposed by the authors in a recent work, where strength of the panels subjected to combined axial force and bending moment was studied accounting for orthogonal to grain timber properties. As advancement, a theoretical moment-curvature model for CLT panels is proposed in this paper and the displacement capacity (i.e., ductility) is investigated. The main parameters which affect the ductile behavior of the panels have been studied by means of parametric analyses, i.e. varying cross-section dimensions, amount of axial force, and hold-downs resistance. Theoretical results have been also compared with numerical ones derived from a bi-dimensional finite element model developed by the authors and a good matching between the results has been highlighted.

Modeling of masonry buildings subjected to seismic actions still represents an open problem in structural engineering. The equivalent frame model is the most used approach to analyze the seismic behavior of both existing and new masonry constructions but, despite this, several aspects are being researched to improve its effectiveness. Among these, modeling of spandrel panels plays a key role to correctly analyze the in-plane seismic response of unreinforced masonry walls. Actually, horizontal mono-dimensional beam-like elements provided of both strength and displacement capacity are used to schematize the spandrel panels, also according with the most of current national and international codes. In this paper an alternative strut and tie scheme to model the spandrel panels, suitable to be used within the equivalent frame approach, is presented: the compressed masonry material is schematized with an equivalent diagonal no-tension truss, whose length and effective compressed area are obtained with limit equilibrium conditions, while tensile-resistant element is represented by no-compression truss. Such model allows a more realistic representation of the mechanical behavior of spandrels because both amount of axial force within the spandrel and the reduced elastic flexural and shear stiffness due to progressive cracking of material are taken into account. Moreover, the local failures of both compressed masonry and/or tensile-resistant elements are better identified and, consequently, also the failure mechanisms of the whole equivalent frame are better detailed. The proposed schematization has been used to simulate the seismic behavior of some reference case studies of existing masonry walls, strengthened with different steel ties arrangement. These walls have been modelled with a hybrid equivalent frame model which consists of mono-dimensional beam-like element for piers, fully rigid offsets for the nodal panels and a strut and tie scheme for spandrels.

This paper deals with the experimental monotonic and cyclic behavior of masonry spandrels reinforced with Fiber Reinforced Polymers (FRP). The research is a part of a wider program, started by the authors in the last decade, regarding the analysis of the seismic behavior of masonry spandrels in historical buildings of the Mediterranean area. The paper summarizes the properties of the test units, the test set-up and the results of the experimental monotonic and cyclic behavior conducted on twenty-four scaled down H-shaped spandrels made with homogeneous material (e.g. mortar with low tensile strength). Both unreinforced and FRP-reinforced specimens with three different slenderness ratios – e.g. slender, intermediate and squat – and three different arrangements of FRP laminates have been considered for the tests. The main objective has been to verify the possibility of preventing brittle failure modes, typical of spandrels subjected to in-plane seismic actions (e.g. diagonal cracking), and of increasing their strength by applying specific reinforcement systems, so encouraging more ductile behavior characterized by toe-crushing at the ends of the spandrels itself.

The whole Mediterranean area historical heritage is mostly constituted by 'ancient' unreinforced masonry constructions which are particularly vulnerable to earthquakes. Due to the particular attitude to out-of-plane collapse mechanisms, 'ancient' constructions largely contribute to increase the seismic risk. In this paper, a methodology for retrofitting unreinforced masonry buildings, aimed to gradually transforms the 'ancient' masonry building into a 'modern' code-conforming building, is proposed. This approach has been applied to an existing masonry building located near L'Aquila (Italy) and damaged during the 2009 earthquake. The results demonstrate the usefulness of a methodological approach to implement retrofitting actions. Thus, appears more easily to calibrate the interventions as a function of the structural weakness and to quantify the role of each intervention in terms of capacity-to-demand ratio. Moreover, a gradual control of the seismic performance enhancement with respect to the original capacity can be achieved, avoiding high economic costs related to unnecessary interventions.

In 2007 the National Research Council published the technical document DT 206/2007 “Instructions for the design, execution and control of timber structures”, with the purpose to provide a technical support to the operators of the sector, in line with the most advanced knowledge at that time. Since then, the world of timber engineering has largely used such document, even though the instructions are not mandatory standard rules, so that they became the most common tool in Italy for the structural use of timber, opening the markets and favoring competition and new applications. In latest years new studies, researches and innovative proposals have promoted the development and the growth of timber constructions also in the civil residential field. The framework of standard rules for constructions and products, both Europeans and Italians, has evolved too. For these reasons, CNR has considered as opportune to proceed to the editing of a new version, updated and widen, namely with the acronym DT 206-R1. The document comes from the spontaneous cooperation of an open group of specialists and operators of the sector, based on a wide discussion on the common scientific and technical expertise and knowledge. The current version has already taken into account the results of the public inquiry phase (concluded by now). The paper presents the main contents of the document, evidencing the innovations. They mainly concerns the following sections: 4) Materials and products; 5) Complementary materials; 6) Elements, typologies and structural systems; 7) Design rules and criteria; 8) Connections; 9) Specific rules for structural types and systems; 10) Design for earthquake resistance. The activity of the committee is still in progress, with the aim of a continuous update.

Il contributo intende discutere il ruolo degli itinerari, intesi come soggetto e Oggetto della narrazione, nella ricostruzione del patrimonio in contesti fragili. Laddove la struttura identitaria appare soccombere, oppressa da processi di urbanizzazione troppo rapidi o al contrario da fenomeni di abbandono, il patrimonio assume il connotato di un progetto da costruire piuttosto che di un insieme di reperti da conservare. Questa tesi trova fondamento in un’idea di patrimonio che mantiene saldo il legame tra la cosa in sé ed il valore che le viene riconosciuto dalla persona - o dalla comunità - che ha il compito di conservare, manutenere, trasmettere. Il tema è esplorato attraverso la presentazione di due progetti elaborati in occasione di concorsi di idee, aventi ad oggetto manufatti non più utilizzati e molto diversi tra loro, ricadenti sul limite dei centri storici attuali di Benevento e Napoli. In entrambi i casi le mappe degli itinerari storici hanno sostenuto la comprensione dei manufatti ricadenti nelle aree di progetto, motivando posizioni forme e dimensioni altrimenti incomprensibili. I progetti assumono a loro volta l’itinerario come tema. Sequenze architettoniche ordinano le tracce stabilendo precise gerarchie, selezionano le memorie da tramandare fino a reinventare un sistema di riferimenti per rigenerare una identità nella quale è possibile riconoscersi.

La ricerca si concentra sulla definizione di un sistema innovativo per la conoscenza, la tutela rigeneratrice e la valorizzazione turistico-sostenibile del patrimonio, favorendo l’aggregazione di competenze scientifico-tecnologiche al fine di rafforzare la competitività dei sistemi locali e delle filiere produttive non solo nei settori dei servizi associati al turismo e beni culturali ma anche in settori ad altissima tecnologia.

Il saggio affronta il tema di alcune architetture del presente che stanno oltre la storia e l’archeologia. Rimandano a spazi primordiali oltre il tempo e ormai senza tempo. E tuttavia intersecano la storia (dato che traducono principi che si riscontrano in diverse epoche dell’architettura con le specifiche declinazioni dei linguaggi) e incrociano l’archeologia (considerato che questa fornisce le testimonianze e le tracce reali di condizioni che altrimenti resterebbero concetti o sarebbero unicamente espressioni di leggende). Sono architetture che riallineano agli inizi e propongono la ricerca di essenzialità, il bisogno di silenzio, la necessità del vuoto.