Antonio Formisano

Low yield metal shear panels as an alternative for the seismic upgrading of concrete structures

The paper addresses the problem of seismic retrofitting of existing concrete structures through an innovative methodology based on low yield metallic shear panels. These panels are introduced in specific places in the concrete structure enhancing its strength and stiffness. However, the most important improvement concerns the energy dissipation capacity of the retrofitted structure. The paper presents a preliminary design methodology within the performance based design framework and details for the realization of the intervention. Elaborated non-linear finite element models are used in order to verify the quality of the results obtained from more simple models used in everyday engineering practice.

Numerical calibration of an easy method for seismic behaviour assessment on large scale of masonry building aggregates

The paper deals with the numerical calibration of a speedy procedure for large scale seismic vulnerability assessment of masonry building aggregates, which are typical building compounds diffused within historical centres of many Italian towns. First of all, based on several numerical analyses developed with the 3MURI calculation program, this simplified assessment procedure has been implemented, it being derived from the well known vulnerability form for masonry buildings integrated by five parameters accounting for the aggregate conditions among adjacent units. Later on, the set-up procedure has been validated through an application to a single building aggregate in the Vesuvius area. Since the results previously achieved have been again confirmed, subsequently the procedure has been used to investigate a wide area of the historical centre of Torre del Greco, allowing for the knowledge of the buildings most at risk under earthquake.Finally, the methodology has been applied to the historical centre of Poggio Picenze (AQ), damaged by the recent Italian earthquake (2009), in order to prove its effectiveness to foresee the damage level experienced by other types of masonry aggregates under seismic actions.

Seismic vulnerability of building aggregates through hybrid and indirect assessment techniques

This work approaches the seismic vulnerability assessment of an old stone masonry building aggregate, located in San Pio delle Camere (Abruzzo, Italy), slightly affected by the 2009 April 6th earthquake occurred in L’Aquila and its districts. This building aggregate has been modelled by using the 3muri® software for seismic analysis of masonry constructions. On one hand, static non-linear numerical analyses were performed to obtain capacity curves together with the prediction of damage distributions for the input seismic action (hybrid technique). On the other hand, indirect techniques, based on different vulnerability index formulations, were used for assessing the building aggregate’s behaviour under earthquake action. The activities carried out have provided a clear framework on the seismic vulnerability of building aggregates, as well as aid future retrofitting interventions.

NUMERICAL ANALYSIS OF SLENDER STEEL SHEAR PANELS FOR ASSESSING DESIGN FORMULAS

In the framework of passive control devices for the seismic protection of new and existing buildings, large attention is getting more focused on Steel Plate Shear Walls (SPSW). Such a system, which is characterized by the use of slender steel panels, has been largely adopted in the last few years both in the North America and Japan. The structural behavior of slender shear walls is strongly conditioned by buckling phenomena, which may have a significant influence also on the ultimate strength of the system, despite the development of stable post-critical behavior due to tension field mechanism. In order to assess the influence of the geometry on the structural behavior of shear plates, in this paper, the theoretical behavior of steel panels in shear, based on existing simplified methodologies (PFI method and strip model theory) is analyzed and then compared to the results obtained by an extensive numerical study carried out by means of accurate finite element models. The comparison between theoretical and numerical results has been developed with reference to different values of the thickness and by varying the aspect ratio of the plate. In addition, the influence of intermediate stiffeners is investigated. On the whole, the obtained results provide useful information for the correct design of slender steel plates in shear to be used as stiffening and strengthening devices in new and existing framed structures.

Theoretical and Numerical Seismic Analysis of Masonry Building Aggregates: Case Studies in San Pio Delle Camere (L’Aquila, Italy)

Masonry building aggregates are large parts of the Italian building heritage often designed without respecting seismic criteria. The current seismic Italian code does not foresee a clear calculation method to predict their static nonlinear behavior. For this reason, in this article a simple methodology to forecast the masonry aggregate seismic response has been set up. The implemented procedure has been calibrated on the results of two FEM structural analysis programs used to investigate three masonry building compounds. As a result, a design chart used to correctly predict the base shear of aggregate masonry units starting from code provisions has been set up.

Cold-formed thin-walled steel structures as vertical addition and energetic retrofitting systems of existing masonry buildings

According to the current trend for sustainable constructions in urban areas, the present paper deals with the analysis of vertical addition systems for energetic retrofitting of existing masonry buildings. Starting from the current European (EN 1998-3:2005) and Italian (NTC 08) technical codes for the seismic assessment of existing structures, first a FEM model has been implemented to investigate the structural performances of masonry units with variable storeys (1, 2 and 3) and material strength (fk = 1, 3 and 6 MPa). Later on, traditional (reinforced concrete, masonry and steel) and innovative (glued laminated timber and cold-formed thin-walled steel) technologies have been proposed as a solution for vertical addition of the studied buildings. Therefore, a numerical campaign of linear dynamic analyses has been undertaken on the examined structures aiming at selecting the best vertical addition solution. The achieved numerical analysis results have provided cold-formed steel systems as the dominant solution for improving the energetic behaviour of the inspected existing masonry buildings. Finally, the achieved numerical results have been confirmed by a consistent and reliable multicriteria decision-making (MCDM) TOPSIS method, where the proposed vertical addition systems have been compared with each other in terms of structural, environmental and economic performance parameters.

Assessment of the Design Provisions for Steel Concentric X BracingFrames with Reference to Italian and European Codes

In the field of construction in seismic areas, the current Italian technical code for constructions NTC2008 is substantially based on the design criteria of Eurocode 8 (EC8), although with some differences. Focusing on steel structures with X Concentric Braces (CB), which is one of the most common seismic resistant structural typology in steel buildings, the paper illustrates a critical review of design methodologies specified in NTC2008, with the intent of providing simplified and more efficient design criteria and procedures able to ensure adequate safety levels under seismic actions, according to the modern design approach. The study is divided in two parts. The first part consists in the design according to the standard rules of typical steel X braced structures by linear analysis, both static and dynamic. The aim is identifying any possible weakness in the current design criteria, with particular reference to both the applicability of the proposed procedures and the actual possibility to size the bracing cross-sections and the connected structural members, like beams and columns. The second part consists in the assessment of the seismic response of structures examined. To this purpose, non-linear static analyses are performed in order to evaluate the most relevant behavioural issues, like the behaviour factor, the failure modes and the effectiveness of the capacity design criteria. Based on the results obtained, a proposal for the enhancement of design criteria is presented.

Local- and global-scale seismic analyses of historical masonry compounds in San Pio delle Camere (L’Aquila, Italy)

Abstract Masonry building aggregates are large parts of the Italian building heritage often designed without respecting seismic criteria. The current seismic Italian code does not foresee a clear calculation method to predict their static nonlinear behaviour. For this reason, in this paper firstly, a simple methodology to forecast the seismic response of masonry aggregates in San Pio delle Camere (L’Aquila, Italy) has been set up starting from the provisions of the Italian Guidelines on Cultural Heritage. The implemented procedure has been calibrated on the results of two FEM structural analysis programs used to investigate three masonry building compounds. As a result, a design chart used to correctly predict the base shear of aggregate masonry units starting from code provisions has been set up. Later on, the large-scale seismic vulnerability and damage appraisal of the inspected historical centre has been done on the basis of a quick methodology, already implemented and experienced by the author in some historical centres of the Campania region. The analysis result was a numerical correlation between vulnerability index and mean damage grade of examined building compounds. In particular, a damage forecast under numerical way has been firstly estimated and then compared with the real one. The post-earthquake scenario has represented an ideal term of comparison for effectively testing the reliability of the employed technique, which should be further extended to other Italian historical centres.

Steel Shear Panels as Retrofitting System of Existing Multi-story RC Buildings: Case Studies

The seismic retrofitting of existing reinforced concrete buildings is currently a major economic and social activities for the redevelopment of congested urban areas. Innovative reversible technologies by metal devices are capable of protecting buildings from damage, providing high levels of structural safety. The current paper is framed within this context, where steel plate shear walls (SPSWs) as retrofitting system of multi-story residential RC buildings, designed for vertical loads and located in the historic center area of Torre del Greco (Naples, Italy), have been used. The vulnerability analysis performed on the inspected buildings have shown their inability to withstand seismic actions. Therefore, the retrofitting design of such buildings through partial bay and full bay SPSWs has been done. The retrofitted buildings behaviour has been assessed through numerical analysis carried out in the non-linear field. The achieved results have shown a significant improvement of the structural performance of the tested improved buildings in terms of strength and stiffness. As a further research development, the available information on the design of SPSWs for retrofitting existing RC buildings will allow to design useful design charts capable of providing the optimal plate geometric dimensions as a function of predetermined performance targets.

Negative and positive incremental forming: Comparison by geometrical, experimental, and FEM considerations

ABSTRACT This study compares negative incremental forming (NIF) and positive incremental forming (PIF) processes by geometrical considerations, finite element method (FEM) analyses, and experimental evaluations. Conical frusta were manufactured starting from AA5052H19 aluminum alloy sheets using both techniques. The processes were also simulated with LS-DYNA software and a close correlation between the experimental and numerical results was observed. The analysis of forming forces, forming limit diagrams (FLDs), and sheets thinning highlights that the PIF technique allows one to reach higher formability and geometrical accuracy. Finally, the differences in terms of surface quality were also discussed.