Time-dependent phenomena as shrinkage and creep in concrete or relaxation in steel, deeply influence 26 the stress and strain patterns of prestressed concrete bridges. Such phenomena are more relevant for 27 staged-constructed bridges, in which a change of the static scheme occurs by the addition of restraints 28 to the initial scheme. The aim of this paper is to develop an approximated procedure allowing to calculate 29 the long-term stress and strain patterns in modern prestressed composite structures. The method is 30 based on the introduction of a suitable number of time intervals depending on the constructive phases 31 of the bridge; then, for each time step, the influence functions of the linear viscosity coefficient are 32 defined together with the variation of this coefficient. The further introduction of the hypotheses of linear 33 behavior of the viscous-elastic strain distribution and the external loads concentrated at the end of each 34 time step, leads to a significant simplification of the problem presented above. The proposed calculation 35 model is used to determine the stress–strain state of the ‘‘Quattroquerce Viaduct’’ located on the highway 36 ‘‘A3’’ Salerno-Reggio Calabria, Italy.

This paper extends a previous study proposed by the same authors in order to assess the response of the critical circular pier under combined axial stress and bending. The moment-curvature relationship of the critical section, given initially as a bilinear curve defined by three parameters (elastic stiffness, displacement at yielding, displacement at collapse), is now defined by a curve at three branches built thank to a more refined purely parametric approach. The main points of the curve (corresponding to the yield strength of steel, the maximum compressive stress of the concrete and the same at the ultimate limit state in confined conditions) are uniquely identified taking into account all contributions provided by technical rules in sections concerning to safety assessments of existing buildings. The methodology provides dimensionless formulations which allow obtain the main coordinates of the moment-curvature relationship. The procedure is simple and easy to use in the vulnerability seismic assessment of bridges but also for evaluation of the rotational capacity of generic RC building elements (beams, columns).

The correct use of non-adherent prestressing techniques in beam-column connections can significantly increase the seismic performance of precast concrete frames, making them a competitive alternative to the traditional cast-in-place concrete structures. In this sense, a fundamental factor of the nodes’ design is represented by the correct calibration of the ratio between the amount of mild steel and that of post-tensioned reinforcements, in order to provide the prescribed flexional and rotational capacity to the beam-column interface, and to guarantee at the same time the required dissipative and re-centering capacity. In this paper, a simple algorithm for the optimal and quick pre-dimensioning of the above mentioned parameters is proposed. It is based on the knowledge of the materials’ mechanical parameters and of the “target” stresses and deformations corresponding to the required performance level, which can be computed either through a Force Based Design approach or by a Displacement Based Design approach. In the case of centered post-tension and in the presence of symmetrical mild steel, the procedure can also be effectively represented in a graphical form, making it is easily possible to determine the post-tensioning stress that should be applied to the cables in order to guarantee that they remain in the elastic field after the seismic event, and to obtain the recentering of the system

A large number of research studies have been recently devoted to the modelling and analysis of infilled RC framed buildings under seismic actions, and the significant role that the infill plays in the overall structural performance is by now a well acknowledged result. In particular, the extension of N2 method to infilled frame allows the appraisal of this contribution within the framework of a non linear static analysis. The present paper reports the results of the non linear static assessment performed for two RC existing buildings located in a high seismic hazard area. Both building are characterized by regularity in plan and elevation, but while the first one is a low rise construction, the second one is relatively tall (7-storey). Thence, there is the possibility of considering two different and interesting situations. For the two case studies, moreover, a complete investigation protocol was previously carried out, providing a detailed experimental information about the materials (concrete, steel reinforcements, masonry infill). Numerical analyses were performed by using spatial models, both for the bare frames and for the infilled frames, in order to appraise the variation of the structural capacity because of the interaction of the infills with the RC elements.

In the last few years, the real-time monitoring of civil infrastructures has become an essential tool for the safety inspection, the design and planning of maintenance. In this context, the implementation of optic fiber sensors within the structural elements is particularly useful in order to check strains and displacements and assess the structural safety level. In this paper, it is presented a methodology aimed at the control of the safety and serviceability level for a Prestressed Reinforced Concrete viaduct. The procedure is based on information acquired by an optic fibre monitoring system implemented during the construction of the bridge. The processing of the data provided by the sensors at different times of the execution (from the casting of the piers to the launching of the deck elements until the completion of the structure) allowed the appraisal of the strain variations related to the load increments and to the stress losses in the different phases and the comparison with the theoretical values. The advantages provided by this procedure in view of the maintenance programs makes it an effective tool for the periodic control of the structural safety of bridges.

Interaction domains for the buckling of isolated R.C. columns are an efficient and versatile instrument for the assessment of the resistance at Ultimate Limit State, and allow the optimization of the structural geometry and reinforcement ratio. The paper presents the procedure for deriving interaction domains for rectangular symmetrically reinforced columns, providing a detailed analysis of the load-carrying capacity for various classes of concrete and reinforcement steel bars. Domains have been obtained according to the “model-column method”, taking into account the uncertainties both in geometry and in the position of axial loads. Effects related to short-term creep are ignored. In order to facilitate the practical utilization, the generic domain has been approximated by a two-branch curve, parabolic and elliptic. The first-one is related to the collapse dominated by axial load, and the second one to flexural crisis. This approximation leads to simple closed-form expressions, particularly suitable for engineering preliminary design.

The participation of masonry infill panel to the overall seismic resistance of a framed building has a significant variation according to the specific mechanical characteristics of the infill, the geometrical distribution within the building and the local interaction among the panel and the surrounding primary RC elements. Especially in the case of structure designed only for vertical loads, essence of the infill can be decisive under an unexpected earthquake, providing an additional contribution to the strength and to the stiffness. On the other side, this beneficial role is often accompanied by the modification of the global collapse mechanisms, with the appearance of brittle failure modes. In the present paper, an existing RC framed building for which a good level of knowledge was available, including a wide experimental database, was chosen as a case study. A reference frame was considered for performing nonlinear static analyses aimed at investigating some significant aspects about the modelling of the infill and the relapse induced by the related computational choices on the structural response. In particular, it is faced the sensitivity analysis about specific parameters involved in the definition of the equivalent strut models: the width bW of the strut; the constitutive Force–Displacement law of the panel; the number of struts adopted to simulate the panel.

La memoria si inserisce nell’ambito delle analisi di vulnerabilità sismica di viadotti con impalcati semplicemente appoggiati su pile monofusto a sezione circolare, ed è riferibile a tutti quei casi in cui la risposta alle azioni orizzontali di natura sismica dell’intera opera d’arte dipende esclusivamente dal comportamento della sua pila critica. La vulnerabilità della struttura nei confronti di un prefissato stato limite è valutata partendo dalla capacità prestazionale (congruente con lo S.L. prescelto) della pila maggiormente esposta e determinando il tempo di ritorno che definisce l’intensità sismica compatibile con la suddetta capacità. Per ciascuno S.L. preso in considerazione, la procedura proposta può essere sintetizzata nei seguenti passi: 1) individuare la curva di capacità della pila, deducibile in maniera speditiva dall’utilizzo di opportuni abachi costruiti sulla base di grandezze adimensionali; 2) risalire al tempo di ritorno C R SL T , che definisce la capacità della struttura per quel livello prestazionale, a partire dalla curva di capacità utilizzando una procedura di analisi statica non-lineare (metodo N2); 3) costruire curve in grado di definire quantitativamente i contributi dei principali parametri (confinamento, armatura longitudinale, massa partecipante al moto, stato di compressione permanente, snellezza,…) che governano la definizione del periodo di ritorno in termini capacitivi C R SL T , in maniera tale che possano essere congruentemente modulati, anche ai fini di previsioni economiche, nel caso di interventi di adeguamento.

The paper presents some developments of a simplified procedure for the assessment of the seismic safety of RC multi-span simply supported bridges proposed by the authors in a previous research work. In this procedure, the capacity curve of the critical pier was obtained by means of a few parameters, known in advanced, concerning the geometry and the masses. Depending on the characteristics of the site (geographic coordinates, stratigraphy and topography), the seismic capacity curve of the most critical pier was first derived, and then, by an inverse application of the N2 Method, the "Capacitive Return Period" is determined for each Limit State (i.e., the return period of the earthquake which corresponds to the actual structural capacity). Starting from this basis, it is proposed a methodological approach able to quantitatively define the contributions of the relevant parameters (confinement, mechanical percentage of longitudinal reinforcement, participating mass; compression level; slenderness of the pier) that govern the structural capacity. The procedure is implemented in an user-friendly numerical/graphical format. These diagrams allow to identify the parameters on which acting for improving the seismic capacity by optimizing the economic cost and the effects obtained in terms of structural capacity and represent, thence, a valid support for the choice and calibration of seismic retrofitting interventions. The whole procedure is presented in a non-dimensional format, in view of the implementation in a specific software that will automatically provide the results on the basis of a few known input data, meeting the design exigencies of the professionals.

This paper proposes a simplified procedure for the seismic vulnerability analysis of multi-span simply supported bridges, in the case of single piers with solid circular sections. The proposed method can be applied whenever the seismic response of the whole bridge depends on the most critical pier. For an assigned limit state, the procedure determines the capacity curve of the critical pier as a function of three parameters (elastic stiffness, displacement at yielding, displacement at collapse), starting from the behaviour under combined axial stress and bending, and then taking into account the different possible collapse modes (shear failure; lap splice failure of the longitudinal bars; buckling) and the geometric nonlinearity. A significant numerical example is presented in which the traditional FEM solution is compared with the proposed simplified procedure

Reinforced concrete slabs are a widely diffused structural solution either in Italy, or abroad; this for a series of advantages connected to their structural conception and their performances. However, this series of advantages is obtained as a result of proper design, especially oriented to appropriately sizing the thickness of the plate itself. Moreover, for flat structures with concentrated loads, as the case of flat slabs on punctual supports, phenomenon of punching can't be neglected, as it inevitably affects the structure and so it must be taken into account even in the early stages of the project. In this paper an attempt to evaluate the reliability of punching verifications has been made, referring to some in force regulations; this has been possible making a comparison between the mean resisting value of punching, obtained applying law prescription and the real collapse load for some columns belonging to a building that collapsed during the early stages of its construction. For the specific case study analyzed, there has been the opportunity to perform an on-site investigation, collecting a great amount of information regarding the mechanical properties of the used materials, the real positioning of the rebars in the structural elements, the real amount of concrete cover and so on. Since in a punching failure mechanism a crucial element is the resistance of the concrete, the precise definition of its properties attains great importance, especially when existing buildings are involved. To analyze the exact conditions of collapse and the factors that may have originated it, an important procedure is the acquisition of information, as much as possible, about the mechanical properties of the onsite materials. After this first evaluation of the accuracy of the actual regulations, another interesting comparison has been carried out, studying the influence of two main factors in the definition of the punching shear resistance; more specifically, it has been observed which is the contribution of the variability of the compressive strength of the concrete on site and the effective depth of the plate. The first related to a series of circumstances that may affect the value of the resistance, reducing it from that established during the design phase, the second closely related to inaccuracy in the laying of the longitudinal reinforcement. Therefore two sensitivity analysis have been performed, either referring to Eurocode 2, or following the prescriptions given in Model Code 2010, varying once the mean value of the compressive strength of the concrete, once the effective depth d.

La stima della resistenza del calcestruzzo di strutture esistenti può essere effettuata con prove distruttive (carotaggi) integrate, in modo opportuno, da informazioni qualitative ottenute mediante prove non distruttive (PND). Un aspetto delicato consiste nello stabilire rapporti affidabili tra i risultati delle PND, i carotaggi ed i valori della resistenza in situ del calcestruzzo. Nella nota vengono preliminarmente analizzati i fattori che maggiormente condizionano la resistenza in situ dedotta dai carotaggi, attraverso una analisi comparativa delle diverse formulazioni presenti in bibliografia per l’elaborazione dei dati. A valle delle osservazioni sulla variabilità dei risultati ottenuti, è proposta una metodologia finalizzata alla stima di un coefficiente correttivo, denominato dagli autori “CDD”, considerante gli effetti di degrado e di rimaneggiamento della carota, con il quale ottenere la diminuzione percentuale ideale di resistenza meccanica (R) del calcestruzzo strutturale rispetto a quella del provino, in funzione del grado di compattazione gc. La metodologia proposta è stata applicata su due campionamenti, costituiti da carote e provini, provenienti dalle indagini condotte su due edifici in c.a., rispettivamente, esistente e di nuova realizzazione. La metodologia consente di quantificare e analizzare criticamente le differenze tra le resistenze misurate sulle carote e quelle dei provini prelevati durante il getto.

The use of macro-modeling approaches based on the concept of the equivalent strut for simulating infill panels presents a number of critical aspects, mainly related to the variability of the results from the parameters adopted (for example: width of the strut, non-linear constitutive law under cyclic actions, assignment of strut mechanical properties in multiple strut models). It should also be observed that it is particularly difficult to identify and calibrate the above mentioned quantities, even if the mechanical parameters of the masonry components (mortar and bricks) are known. It is thence highly desirable to define numerical procedures for aimed at this task, in order to reduce the variability of results due to the characteristics of the equivalent strut. In the present paper, the first results of a procedure aimed at the calibration of the macro-models of infill panels are presented. The adopted methodology directly considers the heterogeneity of materials and the texture effects at the micro-scale, exploiting a "Rigid Body and Spring Model"(RSBM), in which the masonry panel is described as a set of unitary cells constituted by rigid blocks and elasto-plastic springs. The non-linear cyclic law of the equivalent strut is then obtained by a simple numerical identification procedure. The approach has been validated on the basis of some reference experimental tests available in the technical literature, by comparing the experimental results and those obtained respectively by RBSM model and the strut model previously calibrated with the proposed procedure.

The paper concerns the seismic vulnerability assessment of masonry bell towers in Italy, by comparing full non-linear dynamic and non-linear static analysis. An idealized case study is considered, in order to assess some basic and common features of the seismic structural response and to appraise the performance of the proposed approaches. The problem is simplified by using a plane 2D scheme. A specific Rigid Body and Spring Model is adopted to describe the in-plane dynamics. Constitutive laws were assigned following a simplified heuristic approach including the main meso–scale damage mechanisms: i) very low tensile strength; ii) significant post-elastic orthotropy plus texture effects; iii) different rules for post-elastic axial and shear damage; iv) different dependence of the shear strength on the vertical and horizontal axial stress component; v) hysteretic energy dissipation due to cyclic loading. Even using a quite coarse mesh, the model is capable to describe the higher vibration modes with a reasonable computational effort and using realistic accelerograms. Non linear static analysis was performed, by using the RBSM model, obtaining the capacity curve and assessing the seismic demand. A comparison between the two approaches is proposed, in order to appraise the difference in the results and to evaluate quality and significance of results in terms of operational drawbacks and reduction of computational times. Particular attention is devoted to the fact that static non-linear analyses tends to neglect the damage effects induced by higher vibration modes, as well as the influence of the shear response on the global damage.

The purpose of this paper is the validation and application of the vulnerability assessment method based on a simplified survey form for the evaluation of the seismic vulnerability index for masonry and RC buildings: the “ANTAEUS” form. The form has been used for the survey of 4560 buildings in the municipalities of Foggia, Carlantino, Vico del Gargano and Sant'Agata di Puglia. For each one, a sample of the buildings has been extracted and then used for the calculation of the index of vulnerability with the GNDT method, with the purpose of validating the ANTAEUS algorithm. On the basis of these results, a calibration of the parameters involved has been made, introducing some improvements in the form and in the algorithm, with the aim of best matching the GNDT index. Finally, the collected data have been implemented within a GIS software and used to draw a number of significant thematic maps about the vulnerability parameters and the final vulnerability indexe for the four historical towns.

In the last few decades, the scientific community has been extensively involved in the investigation about the interaction between infill masonry walls and RC frames in the seismic structural behavior, both for new and for existing buildings. With respect to this issue, some extensions of the N2 Method have been proposed in order to evaluate the contribution of masonry infill to the structural response. This paper presents an extensive case study regarding the analysis of an existing RC framed building located in a high seismic risk area in Calabria (Southern Italy), for which the project, dated back to the early ‘70s, provided only the presence of vertical loads. In order to collect the data required for the application of the safety assessment procedure and achieve the necessary knowledge level, a broad experimental test campaign was performed on the building in order to assess the condition and quality of both RC elements and infill walls. A number of non-linear static (pushover) analyses were performed on proper structural models of the building, considering both the bare framed structure and the infilled one, in order to appraise the influence of infill walls on the failure mechanisms. In particular, a sensitivity analysis was performed by assigning different Partial Safety Factors (PSF) to the mechanical parameters of infill walls, in order to investigate their effect on the overall structural response of the building.

The object of the paper is the influence the soil-structure interaction on the dynamical response of a masonry tower, for which a high level of stress is involved already in the static field. The relevant deformations and displacements at the base of the tower suggest that a significant volume of ground is engaged into the overall dynamic response, both as a participating mass and as a potential carrier of energy dissipation. In order to investigate this aspect and assess the sensitivity of the dynamic response of the soil-structure system to different soil characteristics, the non linear dynamic response of a case study is analyzed, by including in the model a significant volume of foundation soil and considering two different ground types. The numerical model is based on a specific Rigid Body and Springs approach, able to model the significant inelastic aspects of the constitutive behaviour and the meso-scale damage mechanisms with a moderate computational effort.

In the assessment of existing RC buildings, the reliable appraisal of the compressive strength of in-situ concrete is a fundamental step. Unfortunately, the data that can be obtained by the available testing methods are typically affected by a high level of uncertainty. Moreover, in order to derive indications about the degradation and ageing of the materials by on site tests, it is necessary to have the proper terms of comparison, that is to say, to know the reference data measured during the construction phases, that are often unavailable when the building is old. In the cases when such a comparison can be done, the in situ strength values typically turn out to be lower than the reference strength values (tests performed on taken samples during the construction). At this point, it is crucial to discern and quantify the specific effect induced by different factors: ageing of the materials; poor quality of the placement, consolidation or cure of the concrete during the construction phases; damage due to drilling. This paper presents a procedure for correlating the destructive compressive tests and non-destructive tests (ultrasonic pulse velocity tests) with the data documenting the compressive strength tested during the construction phases. The research work is aimed at identifying the factors that induce the difference between the in-situ strength and cubes taken from the concrete casting, and providing, so, useful information for the assessment procedure of the building.

Ten existing masonry towers, located in the coastal Po Valley (Italy), are analysed in the presence of seismic excitations. They show some affinities which justify a comparative analysis: they are located in the same region and made of masonries having similar mechanical properties, and the majority of them are almost coeval. On the other hand, they exhibit different geometries (e.g. slenderness, thickness of the perimeter walls, height, percentage of perforations, etc.) which may be responsible for their different structural response to the same seismic excitations. Therefore, the aim of the work is to study the effect of the geometry on the seismic behaviour of such towers by assuming as mechanical properties for masonry the ones provided by the technical literature for existing towers in the coastal Po Valley. Full non-linear dynamic analyses are performed by means of a specific Rigid Body and Spring Model (RBSM). This is based on a relatively refined 2D discretization obtained by assembling rigid quadrilateral elements interconnected by non-linear axial and shear springs, exhibiting softening and realistic energy dissipation under cyclic loads. The geometry of the towers is deduced from both existing available documentation (cross-section, front and planar views) and in situ surveys. On the basis of such geometrical data an equivalent 2D mesh is built, where different thicknesses are assigned to adjoining elements, wherever necessary, in order to properly take into account the actual behaviour of the structure within a 2D approach. Four artificial design consistent horizontal accelerograms are applied to the 2D models and the response in terms of collapse mechanisms and force–displacement histories are analysed in detail. Although this study is only a first attempt to analyse the relationship between some typological features of the chosen towers and the structural response they exhibit in the presence of seismic excitations, the results obtained and the comparative analysis that follows are enough to show clearly the strong dependence of the towers’ structural behaviour on their geometric characteristics (slenderness, base shear area, presence of belfry, big perforations, presence/absence of internal vaults, etc.).

L’azione resistente offerta da elementi non strutturali quali le tamponature influenza sensibilmente il comportamento globale e locale degli edifici in c.a. La presenza dei pannelli di chiusura può alterare il cinematismo globale e indurre nelle interazioni nodali con gli elementi del telaio meccanismi di crisi fragile. Nella presente memoria, sono illustrate le risultanze delle analisi statiche non lineari condotte su modelli numerici bidimensionali appartenenti ad un edificio esistente in c.a. sul quale è stata svolta un’ampia campagna di indagine sui materiali. Lo studio è volto a delineare le problematiche inerenti la modellazione delle tamponature ponendo risalto all’influenza sul comportamento non lineare globale, indotta dalla larghezza del puntone equivalente, dalla legge costitutiva per azioni cicliche e dall’uso di modelli numerici multi-biella.

The mechanical characterization of in situ materials is one of the most important issues in the safety assessment of existing buildings, and – especially for masonry structures – represents a major source of uncertainty. In fact, the possibility of achieving a good “Level of Knowledge” is strictly related to the availability of comprehensive experimental tests on the structures, including destructive testing. In the case of masonry buildings, it is very difficult to extract a representative number of “undisturbed” samples or apply alternative techniques (such as in situ diagonal test) without causing unacceptable damages to the structure. The research work presented in the paper concerns the analysis and experimental characterization of a number of “non-engineered” masonry types commonly present in Calabria (a high seismic prone region located in Southern Italy). The definition of non-engineered is actually referred to self-constructed masonry buildings dated back to the first half of the 20th Century, in the absence of any kind of design and technical control about materials and procedures. The attention has been focused on a number of towns in the Province of Cosenza. Here, a survey has been carried out in order to detect and classify the structural features of the buildings: elements, textures, structural configurations. Afterwards, masonry elements and materials have been experimentally investigated (by testing samples taken on site and manufactured in laboratory). All data have been processed and compared with the Italian and European Standards, in order to derive a reference database for the local masonry building types. In a context where it would be very difficult to directly obtain the required experimental information, the objective is to improve the knowledge about local materials and their mechanical features, providing at the same time a reference methodological approach. In the absence of appropriate information (i.e., of a low level of knowledge) the safety verification and vulnerability assessment turn out to be very conservative. It is thence nearly impossible to provide an effective strategy for the rehabilitation/retrofitting against seismic risk, whereas the systematic, complete substitution of the existing residential housing would became the only solution, which is nowadays a non sustainable option.

Da alcuni decenni la comunità scientifica è impegnata ad identificare adeguatamente l‟influenza dei telai tamponati sul comportamento sismico delle strutture in c.a. sia esistenti che di nuova realizzazione. Recentemente in tale ambito, sono state proposte alcune estensioni del metodo N2 per valutare il contributo apportato dalla tamponatura sulla risposta strutturale. La presente memoria, illustra l‟analisi di un edificio esistente ubicato in Calabria, risalente agli inizi degli anni ‟70, progettato per resistere alle sole azioni verticali. Al fine di raccogliere i dati necessari per svolgere le verifiche di sicurezza e raggiungere il Livello di Conoscenza richiesto dalle norme, è stata sviluppata sull‟immobile un‟ampia campagna di indagine sperimentale che ha permesso di valutare la condizione e la qualità degli elementi strutturali e delle pareti di tamponatura. Su modelli strutturali dell‟edificio relativi sia alla struttura nuda che tamponata, sono state effettuate diverse analisi statiche non lineari, per valutare l‟influenza dei pannelli murari sui meccanismi di collasso. In particolare, per valutare l‟effetto delle tamponature sulla risposta strutturale globale è stata condotta un‟analisi di sensibilità assegnando Fattori di Confidenza (FC) diversi alle caratteristiche meccaniche dei pannelli murari.

In the last few years, the real-time monitoring of civil infrastructures has become an essential tool for the safety inspection, the design and planning of maintenance. In this context, the implementation of optic fiber sensors embedded in the structural elements is particularly useful to check strains and displacements and assess the structural safety level. In this paper, a methodology aimed at the control of the safety and serviceability level of a Prestressed Reinforced Concrete Viaduct located in the city of Bari (Italy) is presented. The procedure is based on information acquired by fiber optic monitoring system implemented during the construction of the bridge. The processing of the data provided by the sensors at different times of the execution has allowed the appraisal of the strain variations related to the load increments and to the stress losses in the different phases and the comparison with the theoretical values. This comparison enables a double check: control in the construction phases, safety in the service life.

The dynamic behaviour of an existing building is sometimes difficult to predict, particularly when the information available for the specific case study is not as much as would be necessary for a complete description of the structure. Dynamic response to vibration induced by external natural/artificial sources, thanks to the relative ease with which it can be measured and analysed, makes vibration-based assessment an attractive complement to traditional visual inspection and nondestructive evaluation methods. This study moves from an investigation that is being carried out on a building sited in the port area of Bari, Apulia, where excavation and dredging operations are thought to be responsible for a series of damage that could involve structural and non structural elements in the monitored buildings due to vibration induced in the entire surrounding area. Having the chance to measure the real acceleration and displacement at the basement floor and in some other relevant parts of the building, it will be possible to update the finite element model, matching the response of the FE model in a series of combinations of parameters with the real measured dynamic excitation. Many other studies regarding dynamic identification and the usual modern methods make use of ambient-vibration induced by the so-called environmental noise or, otherwise, inducing a dynamic response by artificial sources of vibration. In this research work the source is known in terms of frequency and magnitude and, so, with an adaptive procedure it will be possible to predict the future damage, serviceability loss or, more generally, the performance of the building towards different combinations of static and dynamic loads

The paper proposes a systematic comparison between two methods of analysis that are well established in the field of earthquake engineering: nonlinear dynamic analysis and nonlinear static procedure (NSP), applied to the out-of-plane seismic response of two masonry façades representative of many ancient Italian churches. The comparison is based on extensive numerical analyses, which focus on the flexural and torsional mechanisms, while the in-plane damage mechanisms and the possible detachment between the façade and the lateral walls because of a poor connection have been presently disregarded. The computations, both in the static and in the dynamic field, are based on a rigid body and spring model specifically implemented for this issue, computationally efficient and equipped with a realistic model of damage and hysteresis at the mesoscale. An innovative aspect of this study is the heuristic modelling of three-wythe masonry, to include some typical texture effects on the macroscale nonlinear response. For each façade, two different masonry textures were considered, performing extensive dynamic analyses that offered a detailed overview about the performance under earthquakes of different intensities. In parallel, NSP and the classical N2-based seismic assessment were applied. A critical discussion and comparison of the results of the two methods is presented to rationally appraise limits and opportunities. In particular, flexural and twisting out-of-plane mechanisms were clearly appraised in the dynamic field, whereas NSPs were not always able to describe the collapse, because they missed the partial failures determined by higher vibration modes, as could be expected.

The compressive strength of in-place concrete is a crucial mechanical parameter which influences the performance level and the safety assessment of existing RC structures both under seismic loads and under dead loads. Italian NTC and Eurocode 8 [1,2] have established that the fundamental basis of the safety assessment is the "Knowledge Level (KL)", which shall be defined according to the procedures adopted for in situ inspection and materials testing (destructive and non-destructive). Within this framework - in the case of RC constructions - a major requirement is the explicit identification of the reference values for the strength of in situ concrete. The afore mentioned building codes, however, do not include any consideration about the uncertainty level affecting the results of in situ tests, which can indeed invalidate the reliability of the mechanical parameters. This problem is instead well addressed by FEMA 356 [3], which prescribes a limit value (14%) to the statistical dispersion of the measures performed on a set of concrete specimens. In this paper, after presenting and discussing a procedure applied for processing experimental data provided by in situ tests in a number of real case studies (school buildings in the Province of Foggia, Italy), the attention will be focused on the problem of the data scattering in the case of in situ concrete strength. It is shown that the variance is a crucial parameter, which should always be considered when performing the safety assessment, even if FEMA requirements, in this respect, are too much restrictive.

The subject of this paper is to propose a seismic vulnerability assessment method based on a simplified survey form. Presently, most part of the mid-scale seismic vulnerability studies in Italy are based on GNDT method proposed by Benedetti and Petrini in 1984 for masonry buildings. Although this method is widely accepted and validated, it requires the compilation of a detailed survey form for each building by a team of specialized engineers. For this reason, the method becomes time consuming and expensive for wide scale seismic vulnerability assessments. The purpose of this work is to propose a simplified form (the ANTAEUS form) that can be quickly compiled by non-specialized technicians with the use of pre-existing documents (plans or land registry files) and by performing a short visit of the building. An algorithm for the estimate of the vulnerability index is also provided, with the aim of matching the GNDT index. The methodology has then been applied for a seismic risk assessment study (the ANTAEUS project) concerning four historical centres of the Province of Foggia

The paper concerns the seismic vulnerability assessment of masonry bell towers in Italy, which is performed by comparing full non-linear dynamic analysis and non-linear static analysis. An idealized case study is considered, in order to assess some basic and common features of the seismic structural response and to appraise the performance of the proposed approach. The reference model is supposed to be structurally independent, i.e. with no adjacent interacting construction. The geometrical dimensions are chosen in order to represent an average north-Italian masonry bell tower, without the intent to cover all the possible situations. The analyses were performed by considering two different materials: poor masonry quality; medium-good masonry quality. The seismic response of these structures involves a coupling between flexural and axial vibration modes, the presence of shear damage patterns, and high vibration modes causing the belfrys collapse. The problem is simplified by using a plane 2D scheme. A specific Rigid Body and Spring Model is adopted to describe the in-plane dynamics. Constitutive laws were assigned following a simplified heuristic approach including the main meso-scale damage mechanisms: i) very low tensile strength; ii) significant post-elastic orthotropy plus texture effects; iii) different rules for post-elastic axial and shear damage; iv) different dependence of the shear strength on the vertical and horizontal axial stress component; v) hysteretic energy dissipation due to cyclic loading. Even using a quite coarse mesh, the model is capable to describe the higher vibration modes with a reasonable computational effort and using realistic accelerograms. Non linear static analysis was then performed, by using the RBSM model, obtaining the capacity curve and assessing the seismic demand. A comparison between the two approaches is proposed, in order to appraise the difference in the results and to evaluate quality and significance of results in terms of operational drawbacks and reduction of computational times. Particular attention is devoted to the fact that static non-linear analyses tends to neglect the damage effects induced by higher vibration modes, as well as the influence of the shear response on the global damage.

For the seismic assessment of existing RC buildings an important question is the reliable appraisal of the in situ concrete strength. This parameter can be performed by resorting to destructive tests (concrete core drilling) properly combined with qualitative information provided by Non-Destructive tests (NDTs). However, there are many factors that influence the results of the experimental tests, and it is difficult to establish whether the value obtained is really representative of the material in situ and if there are alterations which have arisen in time. In the paper, a methodology aimed at the definition of a coefficient called " C DD" is proposed. This coefficient takes into account the effects of the deterioration and alteration of the drilled core, and provides an ideal percentage decrease of the mechanical strength (Δ. R) of the concrete core (with respect to the original one), as a function of the compaction degree g c. The proposed methodology was applied to 2 set of samples, including drilled concrete cores and cubic specimens, respectively coming from an existing and a brand new building. The method allows to appraise and critically compare the difference between the strength obtained from drilling tests and the one measured on the specimens sampled during the casting

The purpose of this paper is to collect the numerical elaboration of resistances measured on cubes made during the concrete casting and on cores extracted after the completion of the structure, for the concrete used in the construction of the “Esaro” Dam facilities (Cosenza, Italy). In addition to the statistical treatment of the sample, aimed at assessing the analytical congruence with the homogeneous classes provided in the design, the influence of compaction degree on in place strength value was qualitatively evaluated. Design/methodology/approach – The reliability of the concrete during the construction phases was evaluated by two analytical control types according to Italian and European technical rules: “production controls” based on statistical processing of resistance values; “laying controls” that serve to assess the compaction degree with a statistical approach. Findings – Results highlighted in the assessing of compliance checks of the mixture, the fundamental relation between statistical approach and concrete laying control. They become important when is necessary to quantify, especially in the case of great infrastructure, the gap between “potential” and “structural” concrete. Originality/value – The advantage obtained by controlling the compaction degree in the construction phase is unquestionable. Specifically, it might allow a reduction of the drilling cores, and so minor structural damage, especially for relatively recent structures favouring extensive non-destructive tests.

During the seismic events occurred in the last decades, the existing reinforced concrete (RC) building stock has often exhibited a significant brittle collapse of joints and secondary elements such as infill walls. A quite common strategy, in the attempt of mitigating this vulnerability, is the generalised implementation of strengthening interventions on the structural elements, even in the absence of a complete seismic assessment procedure. This paper presents some considerations about the effects induced by strengthening interventions involving the tying of the infill panels to the RC frame. Within this context, an appraisal of the actual displacement capacity and the possible alteration induced on the global collapse mechanism is provided. The analyses and discussion of results are presented with reference to an actual case study concerning a school building, which was part of a wide vulnerability assessment investigation performed in the Province of Foggia, Italy. In particular, seismic analyses performed using nonlinear static analysis procedures on the strengthened configuration and on the original structure are critically compared and discussed.

This paper presents a methodology for the seismic vulnerability assessment of current buildings, suitable for the study of historical centres at the regional scale. The applicability is demonstrated with reference to four case studies: the historical centre of the city of Foggia (Italy) and three other small towns of this province, for a total of 4519 housing units. Field data were collected by several teams of technicians by means of a survey form, provided in electronic format. The subsequent data processing and drawing of vulnerability maps was performed using GIS. The collected data were used also for the validation of the algorithm, by comparing the results with those of the GNDT methodology, which is widely adopted in Italy. The results of the research study and the application showed some critical points, related to the poor nature of the information collected and to the reliability of the final results. These issues are analysed and discussed, proposing a strategy for improving the methodology.

Macro-modelling approaches are widely used for assessing the effects of infill panels. However, they contain some specific uncertainties concerning the definition of the equivalent strut (such as the width of the strut, the non-linear constitutive law under cyclic actions and assignment of mechanical properties in multiple strut models) that causes the variability of global structural response. As a result, there is the need to identify what are the parameters that influence the overall response of the building. After the identification of significant parameters, it is crucial to quantify the variation of the results regarding the safety verification of the building. In order to investigate this aspect, for two existing buildings with different heights, using a range of permissible values, the characteristic points (yield strength and maximum point) of the cyclic non-linear law were changed. The procedure has been carried out with the other preliminarily fixed parameters of the equivalent struts. With this approach, a variation of the safety in performance terms was assessed by carrying out a sensitivity analysis of the non-linear cyclic law. The results proposed lay the foundations for further consideration of issues relating to the modelling uncertainties and the development of simplified models for the assessment of existing structures designed to withstand only vertical loads.

The paper presents a study about the monitoring of a pre-stressed reinforced concrete viaduct in Bari (Italy), by means of an optical fiber system embedded into the structural elements. The application case had two objectives: controlling the structural efficiency during the phases of construction, and allowing, in the future, the periodical check of the structural performance under service loads. Sensors were directly anchored to the prestressing strands during the manufacturing phases of the precast beams. By processing and analyzing the data acquired by the system during the different construction phases, it was possible to assess the strain variations related to load increments and stress losses, by comparing them with expected theoretical values. The specific case study shows that the availability of real-time monitoring procedures is nowadays a precious tool for checking the structural safety of critical facilities, in particular bridges.