169,733 research outputs found
Virtual Modernisms. A Digital Investigation on Enrico Castiglioni Structures
No full textIn the 1950s, the reinforced concrete structure became an icon of late modernist architecture, and structural engineers established their expressive languages, focusing on the exploration of cutting-edge geometries. The digitally supported in-depth analysis of this complex geometry architectural heritage represents an open challenge for structural engineering and construction history investigations. This chapter focuses on a work methodology to support historical surveys using 3D modelling, 3D printing, and archival documentation. The study highlights how accurate documental investigation is crucial for constructing 3D models consistent with the represented structures. The 3D models are used as sources of original information to assess the historical documentation and improve the knowledge of ‘the product of the construction’ itself. Regarding complex geometry projects, 3D models improve the insight of the design process and structural conception, while 3D printing provides the physical validation of the anatomy of the structure. The methodology is presented through the case study of the structural designs conceived by the Italian engineer Enrico Castiglioni (1926–2000) in the early 1950s, within the Italian structural engineering international rise
Design of piezoelectric lattice metamaterials
No full textPiezoelectric lattice metamaterials are considered. A computationally-effective homogenisation method is developed based on the recent solution to the Saint-Venant problem for general anisotropic piezoelectric cylinders. A publicly available repository of unit cell topologies is used to identify piezoelectric metamaterials with optimal figures of merit. © 2022, Scipedia S.L. All rights reserved
On the cop number of a graph
No full textThe cop number c(G) of a graph G is an invariant connected with the genus and the girth. We prove that for a fixed k there is a polynomial-time algorithm which decides whether c(G) ≤ k. This settles a question of T. Andreae. Moreover, we show that every graph is topologically equivalent to a graph with c ≤ 2. Finally we consider a pursuit-evasion problem in Littlewood′s miscellany. We prove that two lions are not always sufficient to catch a man on a plane graph, provided the lions and the man have equal maximum speed. We deal both with a discrete motion (from vertex to vertex) and with a continuous motion. The discrete case is solved by showing that there are plane graphs of cop number 3 such that all the edges can be represented by straight segments of the same length
A variational-based fixed-point algorithm for the limit analysis of dry-masonry block structures with non-associative Coulomb friction
No full textThe limit analysis of dry-masonry block structures with non-associative Coulomb friction is formulated as a Mixed Complementarity Problem. Using variational arguments, it is proven that a solution can be constructed by considering a fixed-point problem, which is suitably stabilized and solved by a derivative-free algorithm. The resulting variational-based fixed-point algorithm succeedes to construct a non-associative limit analysis solution by iteratively addressing straightforward associative limit analysis problems. Numerical simulations show that the proposed algorithm is able to predict collapse multipliers of large masonry block structures with accuracy, robustness and effectiveness
The compressive response of additively-manufactured hollow truss lattices: an experimental investigation
No full textThe mechanical response of additively-manufactured hollow truss lattices is experimentally investigated under quasi-static compression testing. Exploiting the recent developments in the Fusing Deposition Modelling (FDM) technique, two families of lattices have been fabricated, obtained as tessellation in space of octet-truss and diamond unit cells. Four specimens for each family of lattices have been designed with prescribed relative density, selecting different inner-to-outer radius ratios r/R of their hollow struts. Compression experiments prove that mechanical properties and failure mechanisms of hollow truss lattices are significantly dependent on the r/R ratio. In particular, a shift from quasi-brittle to ductile mechanical response at increasing r/R values has been revealed for the octet-truss lattice, leading to a stable collapse mechanism and increased energy absorption capacity. On the other hand, a more compliant behaviour has been observed in the diamond lattice response, with a monotonic improvement of mechanical properties as a function of the r/R ratio. Such results substantiate the potentialities of additively-manufactured hollow lattice structures as an attractive solution when lightweight, resistant and efficient energy absorption materials are required. Graphic Abstract: [Figure not available: see fulltext.
Quasi-polynomials, linear Diophantine equations and semi-linear sets
No full textWe investigate the family of semi-linear sets of N-t and Z(t). We study the growth function of semi-linear sets and we prove that such a function is a piecewise quasi-polynomial on a polyhedral partition of N-t. Moreover, we give a new proof of combinatorial character of a famous theorem by Dahmen and Micchelli on the partition function of a system of Diophantine linear equations. (C) 2011 Elsevier B.V. All rights reserved
Frictional behaviour of masonry interfaces: Experimental investigation on two dry-jointed tuff blocks
No full textIn historical masonry structures, featured by dry or weak mortar joints, limit analysis of 3D assemblages of blocks represents a useful tool for the prediction of failure mechanism and collapse load. Results of limit analysis, with no-tension and frictional contact interfaces, are based on the definition of accurate block interface yield domains: experimental and numerical investigations on the frictional contact con- ditions are required. Despite the characterization of shear behaviour of frictional contact was widely studied in the past, limited research is available on the behaviour of dry masonry joints implying interac- tions among shear, bending and torsion. This work aims at presenting an extensive experimental investigation conducted in order to analyse the frictional behaviour of two dry-jointed tuff blocks subjected to load- ing patterns reproducing several possible yield conditions. Besides pro- viding fundamental parameters required for limit analysis formulations, the adopted testing program investigates 3D yield domains of a sin- gle contact interface through different loading scenarios. Moreover, the experimental results are compared with those obtained by a numerical model based on the assumption of rigid blocks which interact through no-tension, frictional interfaces. From the comparison, it is found that the usual modelling hypothesis of ideal interface with all points between blocks perfectly in contact is not always reliable. In fact, depending on the actual contact area and especially in presence of torsion moment, the predicted 3D yield domains may differ significantly from the experimental results
Limit Analysis of Dry Masonry Block Structures with Non-associative Coulomb Friction: A Novel Computational Approach
No full textThelimitanalysisofdry-masonryblockstructureswithnon-associative Coulomb friction is formulated as a Mixed Complementarity Problem. After highlighting some of its peculiar features, such as the lack of uniqueness of the collapse multiplier, a fixed-point based algorithm is presented for constructing a solution, obtained by iteratively solving straightforward associative limit analysis problems. Supported by the comparison with benchmark problems, the resulting procedure is proven to be able to predict the collapse multiplier of masonry block structures with accuracy, robustness and effectiveness
Generalized Thrust Network Analysis of Triangular Masonry Cross Vaults Inspired by Musmeci
No full textA triangular parabolic cross vault, that was designed by Musmeci in the 1950s as a reinforced concrete structure but remained unbuilt, is revisited from the original perspective of its reinvention as a masonry structure. In the framework of static limit analysis under classical Heyman’s assumptions, a generalized thrust network analysis is adopted for a structural safety assessment. The performances of the vault, subject to its self-weight, are investigated through minimum-thrust and minimum-thickness analyses by conforming to the original geometry and assuming the vault thickness as the only design parameter. Further insight is achieved by exploring a more general class of triangular parabolic masonry cross vaults, whose rise-to-span ratio is an additional design parameter. The static efficiency of the smart and unconventional geometry proposed by Musmeci is thus proven, motivating the possibility of bringing it to new life in the form of a masonry structure
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