87,092 research outputs found
Vulnerabilità strutturale e rischio sismico del patrimonio architetettonico: indagini, analisi, modelli
No full textNel volume, dopo avere brevemente delineato il quadro generale del problema, l'obiettivo è quello di fornire una panoramica delle metodologie per la valutazione e riduzione del rischio sismico a scala territoriale e degli strumenti di calcolo, modellazione e indagine sperimentale che possono essere impiegati operativamente per la valutazione della sicurezza di singoli edifici e monumenti.
Nei capitoli di cui si compone il libro, i quattro Autori hanno integrato le rispettive competenze che sono prevalentemente incentrate sulle analisi e metodologie per le valutazioni di vulnerabilità (Uva G.), sugli aspetti modellistici e computazionali (Casolo, S.) e sulla diagnostica (Porco, G. e Porco F.)
Sperimentazione e tecniche diagnostiche per le murature. Metodi di indagine: prove distruttive e non distruttive
No full textBridge monitoring by fiber optic deformation sensors: A case study
No full textIn 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
Assessment of the reliability of Structural Concretes During Execution Phases
No full textThe quality control of concrete is basically an assessment of compressive strength from which also depends the durability of the material. In the case of important constructions, the control of design prescriptions is not always easy. In addition to the uncertainty factors related to the composition of the material, there are also factors relating to the construction phases. These problems are amplified if the production is on site. These reasons can often suggest to perform, destructive and non-destructive test after the completion of the structure, in order to obtain further information about in-place concrete strength. These investigations, if accompanied by appropriate evaluation procedures, allow to determine the degree of concrete compaction, that if unsatisfactory, makes the material more permeable, less durable and less mechanically efficient. This paper collects the numerical elaboration of resistances measured on cubes made during the concrete placing 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 to assess the analytical congruence with the homogeneous classes provided in the design, the influence of compaction degree on in place strength value was qualitatively evaluate, with the aid of an analytical methodology
A finite element with micro-scale effects for the linear analysis of masonry brickwork
No full textIn this paper, we present a two-dimensional finite element able to describe local effects in the linear analysis of periodic brickwork, modelled as a Lagrangean system of rigid bodies interacting by point elastic interfaces. Particular emphasis is given to the description and the implications of the continuum modelling of the Lagrangean system, before the finite element discretization is performed. (C) 2001 Elsevier Science B.V. All rights reserved
Detecção de Cowpea aphid-borne mosaic virus em feijão-de-porco no estado do Pará.
No full textO feijão-de-porco é uma leguminosa utilizada em recuperação e recobrimento do solo e controle de plantas invasoras, por possuir efeito alelopático sobre outras espécies de plantas. A sua produtividade pode ser afetada por doenças, entre elas destacam-se as causadas por vírus. Em Altamira-PA, no campo experimental da Embrapa, observou-se plantas de feijão-de-porco apresentando os sintomas característicos de viroses como o mosaico, nanismo e deformação foliar. Assim, o objetivo deste trabalho foi identificar a espécie de vírus em amostras de feijão-de-porco. Para isso, as amostras foliares foram avaliadas utilizando os testes ELISA e em sequida o de RT-PCR com primers específicos para CABMV (CABMV-F e CABMV-R). No teste de RT-PCR obteve-se a banda esperada de 221 pb correspondente à parte do gene da capa proteica do vírus CABMV. Este foi o primeiro relato de CABMV em feijão-de-porco no Estado do Pará
Comparison between seismic retrofitting solutions for existing reinforced concrete buildings: a case study
No full textIn assessing the safety of existing buildings, the specific actions dedicated to the knowledge of the structure delineate the parameters of the linear or non-linear analysis aimed at identifying the most appropriate structural intervention. In this context, the present paper collects the seismic analysis of a school building in reinforced concrete, illustrating the different stages concerning the acquisition of geometrical and mechanical data, problems about structural modelling and the features of the seismic retrofitting proposed. In closing, a critical comparison between the results derived from some techniques frequently used to seismically improve existing structures
A numerical procedure for modeling the floor deformability in seismic analysis of existing RC buildings
No full textIn the paper is presented a research study on floor system behavior in existing Reinforce Concrete (RC) buildings under horizontal actions. Generally, vulnerability analysis consists in the study of effective structural behavior of buildings, in order to carry out the assessment, comparing seismic demand and structural capacity. To this purpose, the hypotheses at the base of Finite Element (FE) numerical model, as rigid floor assumption, assume a primary role for the accurateness of seismic analysis results. In the study, after carrying out a preliminary assessment on significant parameters, which influence the floor stiffness, a new numerical simplified procedure has been proposed. Starting by micro-models, made with solid elements, on several simple applications, the behavior of floor system in elastic field has been analyzed in terms of in-plane displacements and a thickness of an equivalent shell of orthotropic material has been defined, usable in macro-model of frame-shell elements. Subsequently, using the procedure proposed, a real case of existing RC buildings has been investigated. The results of linear analysis have been evaluated through their comparison with those obtained by a model where the flexibility of slab is simulated with a more consolidate method like “strut model”. The numerical analyses carried out have enabled to give interesting indications about both the accuracy of rigid floor assumption and assessment of slab elements
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