1,720,959 research outputs found
Analisi delle caratteristiche meccaniche di acciai estratti da edifici esistenti in cemento armato
No full textAssessing the vulnerability of existing Reinforced Concrete (RC) buildings is an increasing need for mitigating seismic risk, as clearly demonstrated by recent earthquakes in Italy (e.g. L'Aquila 2009) as well in other countries.
The knowledge process plays a crucial role for a reliable assessment, so that the required actions to reduce the vulnerability through cost effective interventions can be carried out. An accurate knowledge of RC buildings requires that the geometry of the structural system, the amount and detailing of reinforcement, and the properties of the constituent materials are identified.
This work is addressed only to study the estimation of materials' properties and, specifically, of steel. The study is based on the results of tensile testing performed on more than 120 reinforcing bars extracted from public buildings constructed in Basilicata region in the period ‘50s - ‘80s . The sample, made up of both smooth and deformed bars, is a valuable source of information about the real strength of the reinforcement present in existing buildings.
The variation of the main mechanical properties is analyzed along various time intervals, always distinguishing smooth and deformed bars. In addition, a comparison is made between the results obtained in this work and the results obtained using as information source results from original acceptance test reports. This comparison, based on a series of statistical tests, shows that small differences can be found, thus confirming the low variability of the steel mechanical properties when compared to the in-situ concrete properties. From this result useful directions on the appropriate number of tests to be performed on steel can be derived, in order to reliably assess the seismic vulnerability of existing buildings while keeping the number of steel specimens to be extracted as low as possible
Fragility curves of gravity-load designed RC buildings with regularity in plan
No full textIn this paper Fragility Curves (FCs) relevant to existing RC framed building types representative of the Italian building population designed only to vertical load and regular in-plan have been derived from an extensive campaign of non-linear dynamic analyses. In the generation of the FCs, damage states according to the EMS98 scale have been considered while the intensity measure has been defined by adopting an integral parameter, such as the Housner intensity. FCs have been generated by varying different parameters, including building age, number of storeys, presence and position of infill panels, plan dimensions, external beams stiffness and concrete strength. In order to verify the effectiveness of the damage prediction, comparisons were made between the results obtained from the proposed FCs with those deriving from both prominent fragility studies available in the technical literature and damage distributions observed in past earthquakes. Results show that damage grades obtained by adopting the proposed FCs are generally lower than those provided by the other approaches considered. A comparison with real damage data, shows that the proposed FCs generally estimate more severe damage distributions than those observed in past earthquakes, although they give lower differences with respect to the other approaches
Concrete Strength Variability in Italian RC Buildings: Analysis of a Large DataBase of Core Tests
No full textThe knowledge of the materials’ mechanical properties is a preliminary and important step in the seismic vulnerability assessment of existing buildings. In RC structures, the compressive strength of concrete can have a crucial role on the seismic performance and is usually difficult to estimate. Major seismic codes prescribe that concrete strength has to be determined essentially from in-situ and laboratory tests. In some cases such estimation can be complemented by default values
in accordance to standards at the time of construction, therefore analysing the actual concrete properties typically found in RC existing buildings realized in different periods can make available
useful data. To this end, in this paper attention has been addressed to public buildings, namely schools and hospitals. A large database made up of about 1500 test results on concrete cores extracted from about 300 RC public buildings located in Basilicata region (Italy), has been prepared and analysed. The relationships between the actual strength values (mean and dispersion) and the construction period of buildings have been studied. Theoretical distributions to approximate the discrete distributions of strength values in different construction periods have been determined, thus providing relevant data for the structural assessment of individual buildings and, especially, for
large scale vulnerability evaluations
Procedures and experiences in the post-earthquake usability evaluation of ordinary buildings
No full textOne of the most critical issues in the post-earthquake emergency is assessing the usability of buildings in order to restart as soon as possible all the activities in the stricken area while permitting people to go back as safe as possible to their houses. Generally, this is made by means of surveys based on usability forms to be filled out by expert technicians. Different countries adopt different forms whose result in terms of usability is dependent essentially on building damage. The Italian approach accounts for, beyond the damage state, also the vulnerability of the building under examination. In this study, the data collected through the widespread survey performed in the aftermath of the L’Aquila (Italy) 2009 earthquake has been analysed, showing that some buildings judged as not usable although having null or very low damage. Therefore, the role of other causes, among which vulnerability, determining the negative usability outcome has been discussed out. Finally, a practical case faced by the authors during the usability survey in Emilia (Italy) after the 2012 seismic sequence highlights the role of vulnerability on the usability outcome
Experimental evaluation of drilling damage on the strength of cores extracted from RC buildings
No full textConcrete strength evaluated from compression tests on cores is affected by several factors causing differences from the in-situ strength at the location from which the core specimen was extracted. Among the factors, there is the damage possibly occurring during the drilling phase that generally leads to underestimate the actual in-situ strength. In order to quantify this effect, in this study two wide datasets have been examined, including: (i)about 500 core specimens extracted from Reinforced Concrete existing structures, and (ii) about 600 cube specimens taken during the construction of new structures in the framework of routine acceptance control. The two experimental datasets have been compared in terms of compression strength and specific weight values, accounting for the main factors affecting a concrete property, that is type and amount of cement, aggregates' grading, type and maximum size of aggregates, water/cement ratio, placing and curing modality, concrete age. The results show that the magnitude of the strength reduction due to drilling damage is strongly affected by the actual properties of concrete, being inversely proportional to its strength. Therefore, the application of a single value of the correction coefficient, as generally suggested in the technical literature and in structural codes, appears inappropriate. A set of values of the drilling damage coefficient is suggested as a function of the strength obtained from compressive tests on cores
Analisi dinamiche non lineari per la validazione di un metodo speditivo per il monitoraggio sismico di edifici esistenti in c.a.
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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
Sustainable Renovation of Public Buildings through Seismic–Energy Upgrading: Methodology and Application to an RC School Building
Full text linkThere are many existing buildings for which seismic rehabilitation interventions are required, especially in earthquake-prone areas like Italy. At the same time, the deep energy crisis that Europe is facing highlights the need for sustainable techniques that are able to increase the energy efficiency of buildings. In order to mitigate the social and cultural obstacles for deep renovations of buildings, effective techniques and methods are required to avoid relocating users, which often discourages such interventions. To this purpose and as the main novelty, this research is aimed at presenting a new strengthening technique for reinforced concrete buildings that is able to integrate structural seismic strengthening and energy efficiency improvements. It is made up of new framed structures connected from the outside to the existing building, thus reducing the intrusiveness and relocation needs of users. At the same time, the seismic strengthening technique is conceived for an optimal coupling with energy saving interventions like high-performance external insulation finishing systems. In this study, these techniques are described and applied to a reinforced concrete (RC) school building designed only for gravity loads, according to outdated standards. The results show that the considered strengthening technique increases the seismic performance of the building with respect to both life safety and damage limitation requirements, avoiding any further local interventions to the building’s interior. On the other hand, the energy renovation allows for significant savings, since the resulting reduction in the total non-renewable energy consumption is larger than 80%
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
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