Il progetto di laurea (coordinatore Ariella Zattera), seguito come componente del collegio docenti per la disciplina degli Interni sviluppa le problematiche dell'esporre e si serve dell'exibit design per ricucire i rapporti tra la scala vasta del paesaggio salino e quella minuta dell'allestimento degli interni del magazzino del sale di Pier Luigi Nervi.

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.

The assessment of the plastic rotation of reinforced concrete beams is an essential aspect to avoid structural brittle collapses. The value actually available can be generally determined as sum of two different components. The first, due to bending, the second for inclined shear cracks. This paper presents a simplified model which provides the flexural plastic rotation of the rectangular beams with a ``closed-form solution''. The approach is substantially dimensionless and includes main influencing factors the cross -section, as mechanical material properties, ductility, geometrical and mechanical reinforcement ratio, confinement effects. In closing, in order to appreciate the reliability of the procedure, a comparison with models proposed by international technical standards is made

In this paper a simplified procedure to evaluate the seismic vulnerability of R.C. circular piers of bridges with simply supported deck is presented. The methodology starts from the definition of the socalled capacity curve of the pier which take account of the following collapse modes: ultimate curvature, lapsplice failure of longitudinal bars, buckling of longitudinal bars, shear failure, unseating of the deck, second order effects. The vulnerability level of the pier is then evaluated by using a vulnerability index defined for this purpose. The proposed procedure is also able to obtained normalised curves useful to analyse the influence of a single parameter (e.g. transversal confinement, longitudinal bars, seismic mass, slenderness) on the vulnerability index in order to define the best structural intervention necessary to achieve the design seismic performance.

The evaluation of the effects of seismic action on the decks of multi-girder bridges is often neglected by practitioners because it is thought that seismic code prescriptions (i.e., deck elastic behavior and minimum reinforcement) in addition to ultimate limit state reinforcement dimensioning for permanent and variable load, do not justify more accurate analyses aimed at checking and/or optimizing reinforcement layout. With the aim of verifying the reliability of this kind of approach, this article proposes a step-bystep procedure, based on the Strut-and-TieModel, for the design of R.C. girder bridge decks subjected to in-plane seismic actions. As a first application, the proposed approach is used for a single span girder bridge deck. The influence on the model of geometry and supports of the bridge deck as well as the layout of girders and cross-beams is also investigated.

The aim of this paper is to develop a procedure able to calculate the long-term stress and strain patterns in modern prestressed composite structures which are largely influenced by creep and shrinkage and whose final static configuration is the result of many phases of loading and restraints conditions. The introduction of equivalent moduli, depending on the viscous and elastic features of materials, can guarantee a significant simplification of the problem presented above. The proposed calculation model has been used to design the “Quattroquercie Viaduct” located on the highway “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