1,721,117 research outputs found
Linear tetrahedral element for problems of plastic deformation
No full textLinear tetrahedra perform poorly in problems with plasticity, nearly incompressible materials, and in bending. While higher-order tetrahedra can cure or alleviate some of these weaknesses, in many situations low-order tetrahedral elements would be preferable to quadratic tetrahedral elements: e.g. for contact problems or fluid-structure interaction simulations. Therefore, a low-order tetrahedron that would look on the outside as a regular four-node tetrahedron, but that would possess superior accuracy is desirable. An assumed-strain, nodally integrated, four-node tetrahedral element is presented (NICE-T4). Several numerical benchmarks are provided showing its robust performance in conjunction with material nonlinearity in the form of von Mises plasticity. In addition we compare the computational cost of the nodally integrated NICE-T4 with the isoparametric quadratic tetrahedron. Because of the reduced number of quadrature points, the NICE-T4 element is competitive in nonlinear analyses with complex material models
6th International Conference on Mechanics of Masonry Structures Strengthened with Composite Materials, MuRiCo6
No full textThis volume is a collection of edited scientific papers presented at the International Conference on Mechanics of Masonry Structures Strengthened with Composites Materials (MuRiCo6) held in Bologna (June 26-28, 2019)
Assumed strain nodally integrated hexahedral finite element formulation for elastoplastic applications
No full textIn this work, a linear hexahedral element based on an assumed strain finite element technique is presented for the solution of plasticity problems. The element stems from the Nodally Integrated Continuum Element (NICE) formulation and its extensions. Assumed gradient operators are derived via nodal integration from the kinematic-weighted residual; the degrees of freedom are only the displacements at the nodes. The adopted constitutive model is the classical associative von Mises plasticity model with isotropic and kinematic hardening; in particular, a double-step midpoint integration algorithm is adopted for the integration and solution of the relevant nonlinear evolution equations. Efficiency of the proposed method is assessed through simple benchmark problems and comparison with reference solutions
A Multi-Criteria GIS-Based Approach for Risk Assessment of Slope Instability Driven by Glacier Melting in the Alpine Area
Full text linkClimate change is resulting in significant transformations in mountain areas all over the world, causing the melting of glacier ice, reduction in snow accumulation, and permafrost loss. Changes in the mountain cryosphere are not only modifying flora and fauna distributions but also affecting the stability of slopes in those regions. For all these reasons, and because of the risks these phenomena pose to the population, the dentification of dangerous areas is a crucial step in the development of risk reduction strategies. While several methods and examples exist that cover the assessment and computation of single sub-components, there is still a lack of application of risk assessment due to glacier melting over large areas in which the final result can be directly employed in the design of risk mitigation policies at regional and municipal levels. This research is focused on landslides and gravitational movements on slopes resulting from rapid glacier melting phenomena in the Valle d’Aosta region in Italy, with the aim of providing a tool that can support spatial planning in response to climate change in Alpine environments. Through the conceptualization and development of a GIS-based and multi-criteria approach, risk is then estimated by defining hazard indices that consider different aspects, combining the experience acquired from studies carried out in various disciplinary fields, to obtain a framework at the regional level. This first assessment is then deepened for the Lys River Valley, where the mapping of hazardous areas was implemented, obtaining a classification of buildings according to their hazard score to estimate the potential damage and total risk relating to possible slope instability events due to ice melt at the local scale
Preface 7th International Conference on Mechanics of Masonry Structures Strengthened With Composite Materials, MuRiCo 7 2021
No full textThis volume is a collection of edited scientific papers presented at the International Conference on Mechanics of Masonry Structures Strengthened with Composites Materials (MuRiCo7) held online (November 24-26, 2021). The previous Conferences, organised by AICO (Italian Association of Composites in Constructions, established in 1996), were held at the University IUAV of Venice (years 2000, 2004, 2009) and University of Bologna, a campus of Ravenna (2014) and a campus of Bologna (2017, 2019). This International Conference, MuRiCo7, was organized by AICO under the patronage of DICAM Department of University of Bologna, DA Department of University of Bologna, and RILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures). The Conference represented a forum to promote and exchange the latest theoretical, computational, and experimental research works finalised to the design of structural strengthening of historic masonry constructions.
The MuRiCo7 covers a wide range of general topics:
• Mechanics of historical masonry: testing and modeling
• Performance of strengthened masonry with composites (FRP, FRCM, TRM, SRG)
• Performance in masonry/composites coupling: bond, special connections, fracture, fatigue, fire, durability
• Appropriate composites techniques evolution for historical construction strengthening
• First aid and provisional devices in historical structures with collapse risk after seismic shock
• Criticism on existing guidelines, standards, and praxis in masonry/composites coupling
• Sustainability, circular economy, life-cycle assessment, and recycling.
The Editors would like to thank the members of the Scientific Committee and the organizers of the special mini symposiums for their support that contributed to the success of the Conference. Furthermore, we express our gratitude to AICO, promoting and organizing the Conference.
The Editors
G. Castellazzi, C. Gentilini and A. Di Tommaso
ALMA MATER STUDIORUM University of Bologna, November 202
A numerical procedure for the force-displacement description of out-of-plane collapse mechanisms in masonry structures
Full text linkIn this paper, a novel numerical procedure is proposed for the force-displacement description of out-of-plane collapse in masonry structures. The numerical procedure herein proposed represents one first attempt to couple limit analysis-based solutions to displacement-based evolutive analysis strategies. Limit-analysis based solutions are considered trustworthy to investigate collapse mechanisms in masonry structures, even though they cannot be used in displacement-based seismic assessment procedures (e.g. pushover analysis), while displacement-based evolutive analysis strategies (e.g. block-based and anisotropic continuum approaches), which can undertake this last task, are typically computationally demanding and their mechanical characterization is often very challenging. In this research, a genetic algorithm NURBS-based adaptive homogenized upper bound limit analysis is firstly adopted to compute the collapse mechanism that the structure (of any geometrical complexity) experiences for a given loading condition. Then, the 3D geometry of the collapse mechanism is imported in incremental-iterative step-by-step evolutive analysis frameworks to perform pushover analysis. In particular, two numerical modelling approaches are conceived to this aim, both lumping all the mechanical nonlinearities into tight zones located in correspondence of the cracks defined in the collapse mechanism previously computed. The first one uses 3D plastic damaging strips governed by a standard nonlinear continuum constitutive law. The second approach adopts non-standard zero-thickness contact-based interfaces governed by a cohesive-frictional contact behaviour previously developed by the authors for the brick-to-brick mechanical interaction. A number of meaningful structural examples show the effectiveness of the numerical procedure proposed. Pushover curves obtained through different modelling strategies are also critically compared
Editorial: Rising stars in built environment
Full text linkCivil and structural engineering constantly adapts to challenges through technological innovation and novel methodologies. In this Research Topic, we focus on emerging researchers in the Built Environment, aiming to share insights and advancements across the community of young researchers shaping the future of our discipline.
This curated exploration unfolds across three key themes, each representing a cornerstone in the contemporary landscape of civil and structural engineering. These themes encompass the intricate interplay between technological innovation, research advancement, and practical application, collectively steering the evolution of the Built Environment
Assumed-strain finite element technique for accurate modelling of plasticity problems
Full text linkIn this work a linear hexahedral element based on an assumed-strain finite element technique is presented for the solution of plasticity problems. The element stems from the NICE formulation and its extensions. Assumed gradient operators are derived via nodal integration from the kinematic-weighted residual; the degrees of freedom are only the displacements at the nodes. The adopted constitutive model is the classical associative von-Mises plasticity model with isotropic and kinematic hardening; in particular a double- step midpoint integration algorithm is adopted for the integration and solution of the relevant nonlinear evolution equations. Efficiency of the proposed method is assessed through simple benchmark problem and comparison with reference solutions
Modelling the nonlinear static response of a 2-storey URM benchmark case study: comparison among different modelling strategies using two- and three-dimensional elements
Full text linkThis paper aims at comparing the use of different software environments for the study of a simple unreinforced masonry building through nonlinear static analyses. The presented results are part of a wider research project conducted within the ReLUIS consortium, and specifically within a research task whose purpose is providing practitioners with results and tools for an aware employment of commercial software packages for modelling masonry structures. In this study one of the benchmark structures of the research program is analysed; a two-story building characterized by rigid horizontal diaphragms, considering different configurations in terms of openings arrangements and effectiveness of ring beams, is subjected to seismic load conditions. Software packages considering two- and three- dimensional structural models are employed, and the obtained results are compared in terms of capacity curves and collapse mechanisms. One of the critical aspects on the basic assumptions made by software in terms of way to apply the horizontal loads is further investigated. In addition, the role of the shear strength is analysed correlating the mechanical properties to be adopted with micro- and macro- models. The considered models present very different features, and the analogies and differences obtained in the results are critically interpreted in view of the different hypotheses made by the software tools in terms of modelling strategies and adopted constitutive laws
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