Giuseppina Uva

ANTAEUS Project for the Regional Vulnerability Assessment of the Current Building Stock in Historical Centers

ABSTRACT This article presents a methodology for the seismic vulnerability assessment of current buildings, suitable for the study of historical centers at the regional scale. The applicability is demonstrated with reference to four case studies: the historical center 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 geographical information system (GIS) technology. The collected data were used also for the validation of the algorithm, by comparing the results with those of the methodology used by the Gruppo Nazionale per la Difesa dai Terremoti (GNDT [Italian National Group for Defense Against Earthquakes]), 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 analyzed and discussed, proposing a strategy for improving the methodology.

Influence of soil deformability on the seismic response of a masonry tower

The manuscript deals with the dynamic interaction between the seismic response of a masonry bell-tower and the soil layer below its foundations. The study is based on a direct soil-structure interaction analysis, by means of a complete 3D FEM model in which, beside the non-linear behaviour of the masonry material, a large portion of the foundation soil is taken into account, assuming a condition of non-reflection of the elastic waves within the domain of interest by means of infinite elements. A fairly refined description of the tower geometry allowed a thorough examination of the interaction between the characteristics of the motion transmitted from the ground and the damage mechanisms of the tower, which may include crack patterns related to the second mode of vibration and the collapse of the belfry. The results of modal analyses highlighted the extent to which the soil deformability modifies the shape of second natural vibration modes of the tower. A relevant reduction of the high frequency content of the vertical component at the base of the tower was also observed, especially in the case of a more deformable soil. In the non-linear dynamic analyses, a constitutive relation with plasticity and damage for the walls material was assumed, while as forcing actions, the strong ground motions recorded in Mirandola during the shock of May 29, 2012, and in Gemona during the Friuli Earthquake on September 15, 1976 were assumed. These analyses allowed us to investigate two main issues: (1) the capability to take into account the higher vibration modes, which tend to have a relevant role in the damage of the upper part, especially the tower crown and belfry; (2) the specific effect of the vertical component of ground acceleration, usually considered quite relevant for this structural typology. The damage scenarios obtained in a condition of deformable foundation soil resulted different from those obtained in the hypothesis of a fixed base support. In this case, the resort to non-linear dynamical models, which also include a significant volume of deformable soil, is recommended in order to perform an accurate assessment of damage scenarios.

The influence of infilled panels in retrofitting interventions of existing reinforced concrete buildings: a case study

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.

Simplified vulnerability assessment of reinforced concrete circular piers in multi-span simply supported bridges

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.

The assessment of structural concretes during construction phases

Purpose – 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 statist...

Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building

ABSTRACT The new guidelines for the seismic assessment of existing buildings recently introduced by the New Zealand Society for Earthquake Engineering (NZSEE) recommend the Simple Lateral Mechanism Analysis (SLaMA) as an “analytical” first phase of any other numerically-based analysis. This article illustrates the development of the SLaMA method and its validation with reference to an existing RC building severely damaged during the Christchurch earthquake (2011). The capacity of the lateral resisting systems is assessed from component/subassembly to system level. The comparison of the results with observed damage and with the outcomes of refined numerical analyses confirms the effectiveness of this method.

The SonReb Method: Critical Review and Practical Aspects

Current regulations require surveys on materials in order to identify one or more representative values of the in-situ concrete strength. In this context, the SonReb method is widespread. It correlates the in-situ concrete strength with the ultrasonic pulse velocity and rebound-hammer index. The method improves the reliability of both non-destructive methodologies that are less reliable if considered separately. However, the method neglects the numerical dispersion of the acquired resistances, making uncertain the reliability of every representative value identified. Uncertainty is inherent not only in the variability of the parameters that determine the values, but also in the use of literature formulations calibrated on “recurring concretes”, i.e. concretes characterized by properties evenly variables (age, w/c ratio, …) that don’t allow wider use. In this work, a critical review of the SonReb method is proposed, through a purely statistical approach with the aid of surveys on some school buildings in the province of Foggia built in the 60s and 80s.