573 research outputs found
A moving interface finite element formulation to predict dynamic edge debonding in FRP-strengthened concrete beams in service conditions
Full text linkA new methodology to predict interfacial debonding phenomena in fibre-reinforced polymer (FRP) concrete beams in the serviceability load condition is proposed. The numerical model, formulated in a bi-dimensional context, incorporates moving mesh modelling of cohesive interfaces in order to simulate crack initiation and propagation between concrete and FRP strengthening. Interface elements are used to predict debonding mechanisms. The concrete beams, as well as the FRP strengthening, follow a one-dimensional model based on Timoshenko beam kinematics theory, whereas the adhesive layer is simulated by using a 2D plane stress formulation. The implementation, which is developed in the framework of a finite element (FE) formulation, as well as the solution scheme and a numerical case study are presented.</p
An interface approach based on moving mesh and cohesive modeling in Z-pinned composite laminates
No full textAn FE approach based Arbitrary Lagrangian-Eulerian (ALE) and cohesive fracture mechanics is implemented to investigate the effects of debonding mechanisms on the behavior of z-pinned composite laminates. The model is based on the combination of moving and discrete cohesive interface elements, which allow the simulation of interfacial damage or strengthening mechanisms produced by debonding phenomena or z-pinned techniques, respectively. Moreover, complex phenomena such as crack initiation, coalescence mechanisms are easily implemented in both static and dynamic frameworks. Despite existing approaches, available from the literature, the computational procedure is able to overcome difficulties concerning mesh dependence of the solution, numerical complexities and costs involved in the solving procedure. The numerical implementation of the model and its capability to predict debonding mechanisms are discussed with respect different laminate configurations and onset conditions. Moreover, comparisons with existing experimental results available from the literature are developed to investigate the relationship between strengthened and unstrengthened composite laminates
Visual programming for structural assessment of out-of-plane mechanisms in historic masonry structures
Full text linkThis work aims at proposing a novel procedure for the seismic assessment of historic masonry structures which is computationally efficient and does not rely on destructive material tests. Digital datasets describing the geometric configuration of historic masonry structures are employed to automatically generate a non-linear Finite Element (FE) model and investigate on possible collapse modes. A configuration of failure surfaces is therefore detected through the Control Surface Method (CSM), which is here proposed for the first time. In a following step of the analysis, structural macroblocks are identified, whereas an upper bound limit analysis approach is employed to estimate the structural capacity of the structure. Genetic Algorithms are also employed to detect the actual failure mode for the structure. The procedure is implemented into a visual coding environment, which allows one to parametrically explore all possible failure surfaces and immediately visualize the effects of the user assumptions. This is particularly suited to support a decisions-making process which strongly relay on engineering judgement. The procedure is validated by the analysis of two benchmark cases, whose results are presented and discussed
On the elastic and mixed-mode fracture properties of PVC foam
Full text linkSandwich structures are widely used for the design and fabrication of lightweight structural systems, due to their capability to exhibit excellent structural and thermal performances at low material usage. Understanding the phenomena of propagation of macro-cracks in the core and delamination at the face-to-core interface are aspects of great computational interest. Linking sophisticated models with the actual characterisation of their mechanical properties is essential in view of real engineering applications. The elastic and fracture characterisation of the materials composing the core is particularly relevant because its cracking affects the capacity of the sandwich structures to carry out transverse loads. In this work, PVC foams typically used as the inner core in structural applications are investigated over a range of foam densities. Firstly, the elastic properties of foams under compressive uniaxial loading are measured using a full-field methodology. Subsequently, SemiCircular specimens are tested in bending varying the position of supports to generate all range of mixed fracture modes. Suitable fracture criteria are also considered in order to assess their capability to evaluate fracture parameters in PVC foams. Finally, the parameters experimentally determined have been used to validate the response provided by a numerical model developed by the authors
Building resilience and masonry structures: How can computational modelling help?
Full text linkMasonry structures populate European historic centres as both secular and sacred monumental buildings. Several researchers focused on implementing advanced computational strategies to preserve masonry buildings structural integrity. Moreover, today’s tools and workflows offer possibilities for assessing vulnerability, simulating scenarios, and reducing vulnerability are opening new perspectives and challenges. This literature review provides a classification of the analytical and numerical modelling strategies for the structural assessment of unreinforced masonry structures. Finally, two-stepped procedures are discussed and suggested as valuable approaches to combine analytical/analytical, numerical/analytical or numerical/numerical methods.This study has been partly funded by the STAND4HERITAGE project (New Standards for Seismic Assessment of Built Cultural Heritage) that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant No. 833123) as an Advanced Grant. This work was also partly financed by FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020. Their support is gratefully acknowledged. However, the opinions and conclusions presented in this paper are those of the authors and do not necessarily reflect the views of the sponsoring organisations.)
The effectiveness of the DIC as a measurement system in SRG shear strengthened reinforced concrete beams
Full text linkSteel Reinforced Grout (SRG) materials are generating considerable interest as strengthening system of reinforced concrete (RC) structures. They are finding increasing use in several civil engineering applications mainly due to the advantages they offer over traditional material such as high strength to weight ratio, ease of application, durability and low price. This paper describes the results of an experimental investigation carried out on SRG shear strengthened RC beams and gives evidence of the Digital Image Correlation (DIC) effectiveness as a measurement system. The tests performed had two main objectives: (i) assess the effectiveness of continuous and discontinuous U-wrapped jackets comprising a different number of layers and strips; (ii) assess the shear crack distribution during the tests by means of the DIC measurements. The results confirmed that reinforcing RC beams with SRG jackets can increase the load-bearing capacity; when the beam was reinforced with a continuous two-layered SRG strip, an increase of 84% was observed (compared to the unreinforced beam). The Linear Variable Differential Transformers (LVDT) measurements validated the results obtained by means of the DIC
CORRIGENDUM to The mechanisms of acute interstitial nephritis in the era of immune checkpoint inhibitors in melanoma
Full text linkIn this article, the authors’ first names and surnames were incorrectly listed in the wrong order. The correct author list is: Marco Tucci, Anna Passarelli, Annalisa Todisco, Francesco Mannavola, Luigia Stefania Stucci, Stella D’Oronzo, Michele Rossini, Marco Taurisano, Loreto Gesualdo and Franco Silvestris
Real-time Structural Stability of Domes through Limit Analysis: Application to St. Peter’s Dome
Full text linkA digital tool is presented and made available for the rapid structural assessment of historic masonry domes. It is especially suited for masonry domes that present long meridian cracks; ergo partitioned slices governed by a pushing failure mode. The proposed procedure considers a Heyman’s no-tension mechanical model that has been implemented within a user-friendly visual programming environment. The numerical approach includes parametric modelling of the failure mechanism that allows exploring the domain of solutions using the kinematic theorem of limit analysis. A heuristic search method is subsequently adopted to refine the geometry of the collapse mechanism and to compute the value of the horizontal trust. Validation of the results has been achieved considering St. Peter’s dome. As reported in the literature, the behaviour of this dome shifted from a rigid shell-type — stiffened by hoop stresses — towards a pushing type of dome partitioned by long meridian cracks. Unlike time-consuming and advanced methods of analysis, the present procedure allows the users to perform a structural assessment of a historic masonry dome in a few seconds and offers the possibility of including: (i) the dome’s drum in the analysis, if applicable; and (ii) rings as strengthening measure, whose number, position (dome or drum) and material (capacity) are user-defined. The goal is to make the tool easily and freely available at the disposal of students, researchers, and structural engineers
Il momento genetico e l'evoluzione del concetto di furtum in diritto romano. 'Detrahere alteri aliquid'. Per una ricostruzione storica del delitto di furto: genesi, sviluppi, vicende
Full text linkThe work analyzes the original notion of theft in Roman law at the time of twelve tables (450 B.C.) and its subsequent extentions (in a phase of this development several facts were submitted to the punishment provided for theft, such as damage, receiving of stolen goods, fraud, robbery and many others). The author deals also with the principal facets related to juristic elaboration of furtum until the 3rd century
On the elastic properties of PVC foam
Full text linkIn the last decade, sandwich structures spread a great interest in civil engineering applications. However, despite their excellent mechanical performance, they can be affected by macroscopic and microscopic damages, which may trigger catastrophic failure modes. Detailed understanding of the physical and mechanical properties is needed in order to allow refined numerical models to describe structural behaviour under intensive loading conditions, accurately. The elastic and fracture characterisation of the core material is particularly relevant because cracking phenomenon strongly reduces the capacity of the sandwich structures to carry out loads. PVC foams, typically used as the inner core in a structural application, are investigated over a range of foam densities. PVC foams H100, H130, and H200, produced by DIAB. The elastic properties of foams under compressive uni-axial loading are measured using the full-field methodology
- …
