1,721,066 research outputs found
Bézier-based biased random-key genetic algorithm to address printability constraints in the topology optimization of concrete structures
No full textThe advancements of additive manufacturing (AM) technologies are typically coupled with research addressing topology optimization, whose aim is to use optimization methods to achieve effective expressions of free-form design. While many studies emphasize the breakthroughs that topology optimization could bring into structural engineering, there are just a few scientific contributions that address design feasibility, accounting for the technological constraints that characterize the different AM techniques. By formulating a stress-constrained topology optimization problem with a more technologically oriented approach, this study aims to optimize concrete structures while enforcing the cross-section width and path-traceability restrictions that affect the feasibility and performance of geometries obtained through the layered extrusion technique. In particular, this paper proposes a curve-based Biased Random-Key Genetic Algorithm that optimizes stress-constrained structures and generates topologies that can be implemented without post-processing operations. The proposed algorithm, when tested on a diverse set of concrete beam configurations, effectively achieved optimized solutions that used between 81 % and 75 % less material than the full beam configuration. Additionally, each one of the designed topologies adequately met the stress requirements and process-specific constraints. Lastly, two experimental cases also highlighted the printability effectiveness of the proposed approach in conjunction with design of optimized solutions
Analysis of behaviour of costruction under impact and explosions: Approaches for structural analysis, from material modeling to structural responcse
No full textCombining Multiple Loads in a Topology Optimization Framework for Digitally Fabricated Concrete Structures
No full textIn recent literature, topology optimization gathered growing interests given its interplays with digital fabrication and additive manufacturing technologies. Notably, the topological optimization of concrete-like elements requires the study of stress-constrained optimization problems due to strength anisotropy, whose solution presents more challenges with respect to classical stiffness-to-weight maximization. For the purpose of fostering the use of topology optimization techniques in real-application scenarios, in this work we present an iterative algorithm to design lightweight structural concrete elements in presence of multiple load actions, and under the restriction of anisotropic stress-constraints. More specifically, our framework is based on the combined use of a proportional material distribution scheme and a Risk-Factor paradigm, to design performative solutions while limiting the failure probability of the structural element. To validate our approach, we define a parametric set of actions which combine bending and axial load, as commonly utilized in a structural engineering framework. In our computational experiments, we assess the robustness of our method and study the relationships connecting load parameters with the resulting solution properties
Layout-aware Extreme Learning Machine to Detect Tendon Malfunctions in Prestressed Concrete Bridges using Stress Data
No full textIn the past few years, several works focused on the integration of methodologies within the field of Structural Health Monitoring to build reliable automatic damage-assessment procedures. Within this context, only a few papers specifically refer to the automatic assessment of tendon malfunctions in prestressed concrete (PSC) structures, despite the key role that this construction paradigm plays in modern infrastructure networks. This paper describes a novel Extreme Learning Machine (ELM) framework characterized by a layout-aware weight generating procedure (LA-ELM), that analyzes stress data to accurately detect and localize damages affecting the prestressing system of a target PSC bridge. A comprehensive computational study is conducted, testing the proposed methodology of three structural specimens, and comparing the proposed LA-ELM with classical Machine Learning algorithms. The numerical results evidence that the proposed methodology achieves remarkable accuracies in short computational times, and the LA-ELM obtains statistically significant improvements compared to the classical ELM implementation
Mechanical Characterization of Layer-by-Layer Interface in Concrete Elements Obtained by Additive Manufacturing
No full textThe anisotropic behavior of the 3D concrete printing elements represents a crucial key feature to be closely investigated. It is mainly due to the layered extrusion process, the most widespread digital concrete technology, which creates weak planes at the interface, known as “Cold Joints”, by placing material layer upon layer. To investigate the interface bond failure mechanism, the bond strength at the interface between layers was measured in this study, especially with respect to printing time gap between layers. In particular, this work provides a characterization of the mechanical properties of 3D printed concrete elements’ interfaces through the design and the implementation of an experimental setup supported by DIC technique, in order to study the shear behavior of layer interfaces. The study investigates different 3d concrete elements produced with 100 s, 200 s, 1800 s as time gap between layer deposition, showing a significant decrease in terms of maximum load up to about 50% for the elements realized with the higher value of resting time compared to bulk elements
Cement-matrix composites using cfrp waste: A circular economy perspective using industrial symbiosis
No full textThis study aims to provide a mitigation strategy for reducing the economic and environmental impacts of carbon fiber wastes deriving from automotive industry. Recycling and reuse in the construction industry is proposed, according to an industrial symbiosis within a circular economy perspective. Specifically, the process consists of repurposing carbon fiber reinforced polymer (CFRP) scraps/waste into new cement-matrix composites, for which the resulting benefits, in terms of mechanical and environmental performance, are herein described. An experimental campaign, starting with a specific heat treatment of CFRP sheets and an accurate dimensional distribution analysis of the short carbon fibers, is presented. The influence of the fiber content and length on both the workability and the mechanical performance of cement-based carbon fiber reinforced mortars is also evaluated. A reduced amount of either sand or cement (up to 8% and 12.8% in volume, respectively) is also considered in the mix design of the fiber reinforced mortars and derives from the substitution of the sand or binder with an equivalent volume of CFRP fibers. The results show a satisfactory increase in compressive and flexural strength in the range 10–18% for the samples characterized by a volume fraction of fibers of approximately 4% and having a 2–5 mm length. Finally, a life cycle assessment (LCA, 14040/14044) was carried out to quantify the environmental burden reductions associated with the implementation of the proposed symbiotic scheme
A Modified Finite Particle Method: multidimensional elasto-statics and dynamics.
No full textParticle methods are a class of numerical methods that belong to the family of meshless methods and
are not based on an underlying mesh or grid, but rather on any general distribution of particles. They are
nowadays widely applied in many fields, including, for example, solid mechanics, fluid dynamics, and
thermodynamics.
In this paper, we start from the original formulation of the so-called modified finite particle method
(MFPM) and develop a novel formulation. In particular, after discussing the position of the MFPM in the
context of the existing literature on meshless methods, and recalling and discussing the 1D formulation and
its properties, we introduce the novel formulation along with its extension to the approximation of 2D and
3D differential operators. We then propose applications of the discussed methods to some elastostatic and
elastodynamic problems. The obtained results confirm the potential and the flexibility of the considered
methods, as well as their second-order accuracy, proposing MFPM as a viable alternative for the simulation
of solids and structures. Copyright © 2014 John Wiley & Sons, Ltd
In-plane shear behaviour of adobe masonry wallets strengthened with textile reinforced mortar
No full textMany people live in adobe masonry (AM) constructions in earthquake areas even if most of the existing constructions are not engineered, thus prone to seismic damage. Therefore, seismic retrofitting of existing AM structures is a critical issue. In this study, experimental results of diagonal compression tests on 21 adobe masonry wallets, before and after the installation of textile reinforced mortar (TRM) with either hemp or glass fibres, are presented. Hemp-TRM is found to be more effective than glass-TRM in improving the shear capacity of AM, showing a mean increase in shear strength and ductility of 25% and 260% in hemp-TRM-strengthened wallets and 12% and 100% in glass-TRM-strengthened wallets. The hemp textile allowed compatibility of the TRM to the masonry substrate, preventing premature debonding and local failure. Experimental results are compared to existing data on TRM systems made of vegetable fibres, evidencing a significant capacity enhancement through flax- and hemp-TRM systems
Structural E-permits: an OpenBIM, model-based procedure for permit applications pertaining to structural engineering
No full textThis paper investigates the creation and use of integrated IFC models to modernise traditional processes for applications to building authorities for structural engineering approvals and permits. First, we provide a brief overview of e-permit systems in the AEC sector, with the focus on solutions that implement openBIM standards like IFC, MVD, and IDM. Second, we conduct a study on the information requirements of Italy’s seismic-authorisation processes relating specifically to the field of structural engineering. Third, we describe preliminary research on defining the structural engineering information that needs to be incorporated in the IFC format for e-permitting scopes. Fourth, we present our early work on the development of an MVD that would enable the automatic extraction of integrated IFC models. Fifth, we illustrate the reference workflow of the Str.E.Pe. project and propose a preliminary proof-of-concept that makes use of an IFC model, which has been integrated with structural information to support the activities of the building authority in Avellino. The officers there have developed a SWOT analysis using IFC models to assist them in assessing the compliance of structural projects with seismic requirements. Finally, the paper sets out additional research we intend to undertake and our conclusions
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