1,721,490 research outputs found
Experimental study of confined masonry walls under blast loading
No full textTerrorist organizations around the world have used explosives on many occasions to carry out attacks in urban centers. The victims and injuries in these attacks are often due to structural collapses and the impact of debris. This threat leads researchers to study the performance of ordinary building systems exposed to extreme impulsive loads. Confined masonry buildings are a widely used construction system in seismic zones in many parts of the world and have been widely studied under seismic loads. On the other hand, studies of the response to out-of-plane impulsive loads, such as those caused by intentional or accidental explosions, are scarce. In this paper, results of three experimental explosions at different scaled distances are presented. The explosives on and 1 m above the ground were used. Confined masonry walls with and without openings were tested. The complex interaction between air blast and ground shock was analyzed. Levels of damage obtained with different scaled distances are presented. The results are compared with iso-damage curves.Fil: Codina, Ramon Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería; ArgentinaFil: Ambrosini, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería; Argentin
Muros de mamposteria sometidos a explosiones
Full text linkLas organizaciones terroristas de todo el mundo han utilizado explosivos en muchas ocasiones para llevar a cabo atentados en centros urbanos. Algunas de las víctimas y los heridos en estos tentados suelen deberse a colapsos estructurales y al impacto de escombros. Esta amenaza obliga a los nvestigadores a estudiar el comportamiento de los sistemas de construcción ordinarios expuestos a cargas impulsivas extremas. La mampostería encadenada es un sistema de construcción muy utilizadon en zonas sísmicas de muchas partes del mundo, ampliamente estudiados bajo cargas sísmicas. En cambio, son escasos los estudios sobre su respuesta a cargas impulsivas fuera del plano, como las causadas por explosiones intencionadas o accidentales. En este trabajo se estudian 2 explosiones con diferentes distancias escaladas. Se utilizaron explosivos apoyados el suelo cerca de muros de mampostería encadenada con una abertura. Se analizó la compleja interacción entre las ondas de presión y la estructura. Se modela usando codigos comerciales las sobrepresiones, impulsos y la respuesta estructural.Fil: Codina, Ramon Humberto. Universidad Nacional de Cuyo. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Ambrosini, Ricardo Daniel. Universidad Nacional de Cuyo. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaXXVII Congreso Argentino de Mecánica ComputacionalResistenciaArgentinaUniversidad Nacional del Nordeste. Facultad de IngenieríaAsociación Argentima de Mecánica Computaciona
A stabilized finite element method for the two-field and three-field Stokes eigenvalue problems
Full text linkIn this paper, the stabilized finite element approximation of the Stokes eigenvalue problems is considered for both the two-field (displacement–pressure) and the three-field (stress–displacement–pressure) formulations. The method presented is based on a subgrid scale concept, and depends on the approximation of the unresolvable scales of the continuous solution. In general, subgrid scale techniques consist in the addition of a residual based term to the basic Galerkin formulation. The application of a standard residual based stabilization method to a linear eigenvalue problem leads to a quadratic eigenvalue problem in discrete form which is physically inconvenient. As a distinguished feature of the present study, we take the space of the unresolved subscales orthogonal to the finite element space, which promises a remedy to the above mentioned complication. In essence, we put forward that only if the orthogonal projection is used, the residual is simplified and the use of term by term stabilization is allowed. Thus, we do not need to put the whole residual in the formulation, and the linear eigenproblem form is recovered properly. We prove that the method applied is convergent, and present the error estimates for the eigenvalues and the eigenfunctions. We report several numerical tests in order to illustrate that the theoretical results are validated.Peer ReviewedPostprint (author's final draft
Numerical and analytical study of overpressures and impulses inside a masonry box subjected to external blast loading
No full textBlast loads have attracted considerable attention in recent years due to accidental or intentional events involving important structures, which have occurred around the world. The activities related to terrorist attacks have increased and, unfortunately, the current trend suggests that they will continue to rise in the future. In relation to the design of structures subjected to blast loadings, there are still many uncertainties in the specialized technical literature. Particularly, the overpressures and impulses inside constructions are difficult to estimate due to many reflections of the shock wave. The main objective of this work is to study the propagation of the blast wave inside constructions subjected to external loadings. An experimental study was performed using a masonry box with reinforced concrete beams and columns and a typical window. The results were previously presented. In this article, numerical models are developed in order to compare results and to obtain design guidelines. Explosive charges of equivalent 1?5 kg of TNT and elevated 1m above the ground were detonated at different distances from the window, and overpressures and impulses were obtained at five points inside and outside the room. However, empirical?analytical results using a well-known technical manual are also obtained and compared. The obtained results are useful to evaluate numerical codes and empirical formulas.Fil: Codina, Ramon Humberto. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Ambrosini, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico; Argentin
Full-scale testing of leakage of blast waves inside a partially vented room exposed to external air blast loading
No full textFor the last few decades, the effects of blast loading on structures have been studied by many researchers around the world. Explosions can be caused by events such as industrial accidents, military conflicts or terrorist attacks. Urban centers have been prone to various threats including car bombs, suicide attacks, and improvised explosive devices. Partially vented constructions subjected to external blast loading represent an important topic in protective engineering. The assessment of blast survivability inside structures and the development of design provisions with respect to internal elements require the study of the propagation and leakage of blast waves inside buildings. In this paper, full-scale tests are performed to study the effects of the leakage of blast waves inside a partially vented room which is subjected to different external blast loadings. The results obtained may be useful for proving the validity of different methods of calculation, both empirical and numerical. Moreover, the experimental results are compared with those computed using the empirical curves of the US Defense report/manual UFC 3-340. Finally, results of the dynamic response of the front masonry wall are presented in terms of accelerations and an iso-damage diagram.Fil: Codina, Ramon Humberto. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Ambrosini, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; Argentin
New sacrificial cladding system for the reduction of blast damage in reinforced concrete structures
Full text linkOver the past few decades, explosive devices have become the weapon of choice for many terrorist attacks. In some of these attacks, large amounts of explosives are detonated within a short distance of building structures. It has been shown that current design methods are inadequate for the prevention of progressive collapse. The protection of key elements, such as columns, is necessary to prevent this catastrophic response sufficiently. This article discusses the performance of a new sacrificial cladding that protects reinforced concrete members under blast loading. It consists of reinforced resin panels with an insulation layer. For comparison purposes, two reinforced concrete members were previously experimentally studied, a reinforced concrete column without protection and reinforced concrete column with classical steel jacketing. It can be observed from the experimental results that the new sacrificial cladding achieves an important reduction in damage and displacements.Fil: Codina, Ramon Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; ArgentinaFil: Ambrosini, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; ArgentinaFil: de Borbon, Fernanda Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; Argentin
Alternatives to prevent the failure of RC members under close-in blast loadings
Full text linkIn this paper, an experimental study of the dynamic response of reinforced concrete (RC) members protected in different ways is presented. Two alternatives for the protection of RC members are designed and studied; classical steel jacketing and a new reinforced polyurethane sacrificial layer. The mitigation of shock and absorption of energy from the blast is studied with experimental methods. For comparison purposes, a RC member without protection is also tested and studied. As expected, the steel jacketing provided excellent protection reducing the maximum final deflection as well as reducing damage to the member. On the other hand, the proposed reinforced polyurethane protection performed reasonably well. The obtained results are useful for exploring new alternatives for the protection of RC columns as well as for the calibration of numerical codes.Fil: Codina, Ramon Humberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; ArgentinaFil: Ambrosini, Ricardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; ArgentinaFil: de Borbon, Fernanda Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería. Instituto de Mecánica Estructural y Riesgo Sísmico. Maestría en Ingeniería Estructural; Argentin
Alternatives to prevent progressive collapse protecting reinforced concrete columns subjected to near field blast loading
Full text linkExtensive research activities in the field of blast loads have taken place in the last few decades. Explosive blast research is important not only for the understanding of damage caused by explosions but also for predicting vulnerability of structures and human to blast and for the development of blast-resistant materials and protective elements. In this sense, the façade columns in buildings are key elements to protect in order to avoid progressive collapse. In this paper, a numerical-experimental study of the dynamic response of reinforced concrete (RC) columns with different sacrificial layers of protection is presented. Different alternatives of protection of RC columns are designed and studied, from classical steel jacketing to crushable materials. The mitigation of shock and absorption of energy under blast loading conditions is studied by numerical and experimental methods. For comparison purposes, a RC column without protection is also tested and studied. The obtained results are useful to explore new alternatives of protection of RC columns as well as to calibrate numerical codes.Fil: Codina, Ramon Humberto. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Ambrosini, Ricardo Daniel. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: de Borbon, Fernanda Maria. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin
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
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