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Active Confinement of Structural Members for Seismic Strengthening of R/C Frame Buildings
No full textActive confinement (AC) of structural members is gaining growing attention in the academic and professional
communities as advanced seismic retrofit strategy of buildings. The study presented here is focused on the application of a highly
performing AC technology, so named CAM (Active Confinement of Masonry), conceived over than twenty years ago in Italy for
masonry structures, and subsequently adapted with effective results to reinforced concrete ones (named, for extension, CAM-R/C).
A representative case study is particularly examined, i.e. a school built in the early 1960 in Friuli Venezia Giulia region, Italy. A
seismic assessment analysis of the building is carried out in its current conditions, also supported by preliminary diagnostic
investigations, which highlights several seismic deficiencies, especially in terms of shear response of columns and beams.
Thus, a retrofit intervention based on the application of the CAM-R/C system is designed, which allows attaining a substantial
improvement of the structural performance.
A detailed description of the case study characteristics, the design criteria adopted for the considered seismic strengthening strategy,
drawings of the interventions, and a synthesis of the seismic analyses developed in original and retrofitted configurations are offered
in the pape
Stiffening effects-controlling sizing procedure of ADAS dampers in seismic retrofit of frame structures
Full text linkAdded Damping and Stiffness (ADAS) steel dissipators are among the most classical devices installed in dissipative bracing systems for the advanced seismic retrofit of frame buildings. An energy-based sizing procedure is formulated in this study for this class of dampers, where the total number of constituting plates is directly related, without iterative steps, to the supplementary damping energy required to jointly reduce stress states in structural members and storey drifts. The stiffening effects of the dissipative braces are expressly controlled, so as to compensate for the increase in storey shears induced by their incorporation in the frame skeleton. The sizing procedure is demonstratively applied to the retrofit design of a 6-storey reinforced concrete building, to explicate and discuss the use of its analytical relations and relevant limitations in practice. The evaluation of the seismic performance of the structure in retrofitted conditions allows comparing the response of the dissipative bracing system with the hypotheses formulated at the sizing stage
Structural performance study and improvement of Artemio Franchi Stadium in Florence
Full text linkArtemio Franchi Stadium in Florence is the first world-famous work by Pier Luigi Nervi, and is celebrated as a masterpiece of the Rationalist movement. In view of this, it has been declared a work of cultural and historical interest by the Italian Ministry for Cultural Heritage and Activities, with several specific preservation restrictions on its most distinguishing structural and architectural elements. With a view to the recently planned restyling and modernization works, a diagnostic field survey and testing campaign, and a static and seismic performance assessment study of the Stadium were commissioned by the Municipality of Florence. Furthermore, a retrofit design respectful of the architectural preservation requirements was requested for its reinforced concrete structure. The contents of the diagnostic and assessment study, as well as of the retrofit design, are presented in this paper. The results of the structural analyses, carried out by means of a detailed finite element model calibrated on the field survey and testing data, show slightly unsafe static conditions in less than 10% of the beams and columns constituting the bleacher sloped frames, and diffused unsafe conditions under seismic action scaled at the Basic Design Earthquake level. The proposed retrofit solution consists in incorporating dissipative braces equipped with fluid viscous spring-dampers in several spans oriented in orthogonal direction to the bleacher frames, and installing fluid viscous pure dampers across the majority of the technical separation gaps between adjacent bleacher blocks, so as to prevent their mutual pounding. The results of the analyses in retrofitted conditions highlight a transition to safe conditions for more than half of the unsafe members, and a remarkable reduction of the demand/capacity ratios in the remaining members. Safe stress states can be reached in the latter by means of simple additional local strengthening interventions. This substantial improvement of seismic performance is achieved with a minimal visual and functional impact on the existing structures, as prescribed by the imposed preservation restrictions
Local retrofit of reinforced concrete structures by the acm system
Full text linkDuring the last decades, low architectural impact strategies have been increasingly adopted in the seismic retrofit of reinforced concrete structures. Among the emerging technologies in this field, the active lateral confinement of columns, beams, and beam-to-column joints is gaining growing attention thanks to the localization of the interventions only on the members in unsafe conditions, the resulting small increase in size, and the limited demolition required for installation. The study presented herein is focused on the application of a highly performing confinement technology, named as ACM (Active Confinement of Masonry), which was conceived more than twenty years ago in Italy for masonry structures, and then successfully applied to reinforced concrete ones. A representative case study is examined in detail herein, i.e., a school built in the early 1960s in the Friuli Venezia Giulia area in Italy. A seismic assessment analysis of the building is carried out in its current state, also supported by preliminary diagnostic investigations, which highlights several seismic deficiencies, especially in terms of shear response of columns and beams. Thus, a retrofit hypothesis based on the installation of the ACM system is proposed, which allows attaining a substantial improvement in the seismic response capacities, while maintaining limited architectural intrusion. A detailed description of the case study characteristics and a synthesis of the time-history seismic analyses developed in original conditions are presented in this article, along with the design criteria, drawings of the interventions, and an evaluation of the resulting performance enhancement in retrofitted configuration
A case study of modern heritage building: Base isolation seismic retrofit for preservation of its architectural distinguishing features
Full text linkSeveral Italian buildings designed by eminent architects and structural engineers in the second half of the 20th century are now included in modern heritage listings. At the same time, as they were designed before the issue of coordinate national Technical Standards, often require important structural rehabilitation interventions. One of the most representative case studies of that period in Florence, i.e. the building now housing the Automobile Club Headquarter and a B&B Hotel, is examined in this paper. A seismic assessment analysis carried out on the structure highlighted strength deficiencies in several members and potentially severe pounding conditions between the two constituting wings of the building, separated by a narrow technical gap. In order to improve the seismic performance without altering the architectural appearance of the building, characterized by large windows in the façades, free internal spaces and elegant proportions of the main structural members, a base isolation retrofit hypothesis is proposed. A substantial seismic improvement is obtained in rehabilitated conditions, as assessed by the achievement of safe stress states for all members up to the basic design normative earthquake level, as well as of maximum relative lateral displacements of the two wings constrained below the technical gap width
Enhanced seismic retrofit of a reinforced concrete building of architectural interest
Full text linkModern heritage buildings designed in the 1950s and 1960s often feature poor seismic performance capacities and may require significant retrofit interventions. A representative case study in Florence, i.e., the edifice housing the Automobile Club Headquarters, is examined here. The building was designed in 1959 with an articulated reinforced concrete structure and presents some enterprising solutions for the time, including suspended floors accommodating large glazed curtain wall façades in the main halls. The original design documentation was collected with accurate record research and checked with detailed on-site surveys. Based on the information gained on the structural system by this preliminary investigation, a time-history assessment analysis was carried out. Remarkable strength deficiencies in most members and severe pounding conditions between the two constituting wings, which are separated by a narrow technical gap, were found. As a result, a base isolation retrofit hypothesis is proposed in order to improve the seismic response capacities of the building without altering its elegant architectural appearance, being characterized by large free internal spaces and well-balanced proportions of the main structural members. A substantial performance improvement is obtained thanks to this rehabilitation strategy, as assessed by the achievement of non-pounding response conditions and safe stress states for all members up to the maximum considered normative earthquake level. Furthermore, the very low peak inter-storey drifts evaluated in retrofitted conditions help in preventing damage to the glazed façades and the remaining drift-sensitive non-structural components
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Multi-storey Building Retrofit by ADAS- Equipped Braces
Full text linkIncorporation of dissipative bracing systems is an emerging seismic retrofit strategy for frame structures. Among the
several types of devices currently adopted as passive protection elements, Added Damping and Stiffness (ADAS) steel
dissipaters have a well-established tradition. This is a consequence of their plain working principle, based on the
elastic-plastic behaviour of the constituting plates, as well as of their relatively easy installation. In spite of this, the
design of ADAS dampers is not simple, because it requires a proper balance between the addition of energy dissipation
and horizontal translational stiffness. An energy-based design criterion is formulated to this aim in this study, which
directly relates the total number of plates of the dissipaters to the supplemental damping energy needed to jointly
reduce stress states and storey drifts, expressly taking into account the reduction of the fundamental vibration period
due to the stiffening effect of the bracing system. A seismic retrofit intervention is demonstratively designed by
applying this criterion for a 6-storey building with reinforced concrete structure, an assessment analysis of which
shows poor seismic performance capacities. A comparative analysis among three different installation hypotheses of
the ADAS devices allows to select the distribution capable of attaining the best performance of the retrofit measure
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