1,720,984 research outputs found
Nonlinear modelling of the seismic response of masonry structures: Calibration strategies
Full text linkIn this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards
Automatic Calibration of Constitutive Models in STKO Pre-Processor
No full textSTKO was recently presented by some of the authors as an innovative pre- and post-processor for OpenSEES motivated by the lack of suitable tools for the simulation of real scale complex structures that require a high volume of data for visualization. One of the most interesting features of STKO is its Python-based scripting interface that allows customization and extension of both the pre- and post-processor modules. The main aim of this work is to show the suitability of the scripting interface of the pre-processor by implementing a set of tools to support the user in handling and improving constitutive laws available in OpenSEES. A first tool deals with the automatic calibration of constitutive laws starting from available experimental data by means of optimization algorithms. The second tool focuses on the confinement of concrete. Starting from the definition of a constitutive law for unconfined concrete and from the section geometry, it computes the parameters of the confined model. Finally, some examples demonstrate the usefulness of these tools for the analysis of RC structures
Tension-Compression Damage Model with IMPL-EX Algorithm for Micromodeling of Masonry Structures
No full textA tension-compression continuum damage constitutive model was recently proposed by some of the authors and applied to the continuous micro-modelling of masonry structures. The model features two damage parameters, for tensile and compressive stress states, to handle the unilateral effect of masonry. It was also demonstrated how the 2-parameter model can represent, even if in an approximate manner, the dilatancy of mortar joints, which is something that is not explicitly handled by damage models as it is with plasticity models. To overcome the convergence issues that arise from the softening behaviour of masonry, the proposed model is here improved by implementing a mixed implicit-explicit (IMPL-EX) constitutive integration algorithm. This work discusses the theory of the constitutive model, its implementation in OpenSEES, and its usage in OpenSEES solver and STKO pre- post- processor for the analysis of masonry structures via the micro-modelling approach
REFINED MODELLING AND ANALYSIS OF BUILDING AGGREGATES FOR THE ASSESSMENT OF SEISMIC RESPONSE
Full text linkUnreinforced masonry (URM) buildings constitute a large portion of Italian-built heritage. URM
derive from the process of expansion, completion and transformation of the structural units, especially in the
historical city centers. Masonry aggregates can be arranged in a large number of possible configurations,
which can include different interstorey heights, different number of stories, different planar shapes and different
masonry typologies. However, the major uncertainty is related to the degree of connection between the
structural units, which significantly conditions the response. Because of these reasons, the assessment of
URM aggregate is not simple and deserves in-depth investigation. In this paper, a reference building aggregate
is modelled and analyzed under different arrangement conditions. The numerical model makes use of
homogenized masonry approach by means of 2D shell-layered elements, which can account both for the inplane and out-of-plane response. The model is realized with the STKO software platform for OpenSees.
Different boundary conditions are analyzed, namely the deformability of floors, and the composition of the
aggregate. Nonlinear static and dynamic analyses are carried out for the different case-studies highlighting
the influence of the aforementioned conditions on the response of the structural units and on the extent of the
so-called “aggregate effect”
Seismic Response of different masonry building aggregate configurations by a refined FE micromodel
Full text linkUnreinforced masonry (URM) aggregate buildings represent a significant portion of Italianbuilt heritage, especially in historical centers. These structures derive from the progressive
transformation of structural units during the time, for example, because of the addition of new
structural portions to existing ones. Masonry aggregates are characterized by a large number
of possible configurations, including different interstorey heights, number of stories, different
planar shapes and various arrangements of the masonry and structural details. Moreover, the
degree of connection between the structural units is a relevant element of uncertainty conditioning the response. This paper presents a numerical study investigating the behavior of a
reference-building aggregate by examining two different boundary conditions: the rigid diaphragm and the flexible diaphragm. The adopted numerical model employs a homogenized
masonry approach by means of layered 2D shell elements. The models are realized with the
STKO software platform for OpenSees. Nonlinear static analyses are carried out for the different case-studies highlighting the influence of the aforementioned parameters on the inplane response of the structural units and the extent of the so-called “aggregate effect”
Flexural strengthening of RC slabs with SRP/SRG: an experimental-numerical comparison
No full textSteel reinforced polymer (SRP) and steel reinforced grout (SRG) systems have emerged as promising and cost-effective technologies for the external strengthening of RC structures. An experimental campaign was recently performed to investigate the effectiveness of SRG/SRP systems in increasing the flexural strength of RC slabs. Test results are herein used to validate a Fiber based finite element code developed with the aim of simulating the flexural behavior of SRP/SRG strengthened RC beams/slabs. The model provides an accurate prediction of the crosssectional response by explicitly modeling each constituent, their position inside the discretized cross-section, and their nonlinear behavior. The satisfactory comparison between numerical predictions and experimental results assessed the accuracy of the developed code
Multiscale computational first order homogenization of thick shells for the analysis of out-of-plane loaded masonry walls
Full text linkThis work presents a multiscale method based on computational homogenization for the analysis of general heterogeneous thick shell structures, with special focus on periodic brick-masonry walls. The proposed method is designed for the analysis of shells whose micro-structure is heterogeneous in the in-plane directions, but initially homogeneous in the shell-thickness direction, a structural topology that can be found in single-leaf brick masonry walls. Under this assumption, this work proposes an efficient homogenization scheme where both the macro-scale and the micro-scale are described by the same shell theory. The proposed method is then applied to the analysis of out-of-plane loaded brick-masonry walls, and compared to experimental and micro-modeling results
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
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