Search results for "Civil Engineering"
showing 10 items of 1216 documents
A strategy for the finite element modeling of FRP-confined concrete columns subjected to preload
2018
Abstract Compressive behavior of columns strengthened by means of an outer elastic confinement provided e.g. by fiber-reinforced polymer (FRP) jackets has become a main topic in the field of structural retrofitting. In details, the problem of the response assessment of strengthened columns is still under study. Many analytical formulations have been proposed to describe the compressive behavior of confined concrete under both monotonic and cyclic loads. However, the effect of a stress/strain level in the columns already present prior to apply the confinement has been generally neglected until now, also because of the lack of well defined strategies of modeling. In this frame, here, (1) a FE…
MICRO-SCALE STUDY OF RESIDUAL STRESSES IN CR2O3 COATINGS SPRAYED BY APS
2020
International audience; Whichever the application field, every material forming process generates residual stresses on the surface. While they are likely to enhance the aimed properties of the final mechanical part, these stresses may also drastically reduce them and result in early failures. Therefore, understanding the residual stress state remains a major challenge when coating complex parts, especially as most characterization methods at the microscopic scale involve specific sample preparation procedures which may affect the residual stresses field. This work investigates the residual stress state that exists in chromium oxide coatings deposited via Atmospheric Plasma Spray (APS), usin…
Crack growth models for multiaxial fatigue in a ship’s propeller shaft
2021
Abstract A premature fatigue failure of a large intermediate propeller shaft in a shuttle tanker is discussed and analyzed. The short fatigue life consists mainly of a crack growth phase. Life predictions are carried out by crack growth modelling based on engineering fracture mechanics. The purpose of the present investigation is to identify the most likely loading modes based on the evolution of the crack propagation. A Linear Elastic Fracture Mechanics Model (LEFM) is applied with the stress intensity factor range entering the Paris law as a key parameter. Existing formulas for the geometry functions are supplemented by more detailed stress intensity factor calculations pertaining to smal…
Discontinuous FRP-Confinement of Masonry Columns
2020
Recent seismic events, all over the world, demonstrated that masonry constructions are prone to brittle collapses when shear or compression capacity is reached. It is clear that, in many real cases, masonry columns need to be strengthened for enhancing their load-carrying capacity and to develop a more ductile response. The Fiber Reinforced Polymers (FRPs) confinement of masonry columns is a well-known technique that may produce these advantages. Unfortunately, full-wrapping insulates the column from the environment; so interstitial humidity can easily occur and cause the acceleration of the masonry's decay. In order to prevent it, partial-confinement is commonly assessed instead of total-j…
Lessons Learned on the Tensile and Bond Behavior of Fabric Reinforced Cementitious Matrix (FRCM) Composites
2020
Fabric Reinforced Cementitious Matrix (FRCM) composites represent an effective, compatible and cost-efficient solution for strengthening and retrofitting existing structures. A strong research effort was done to investigate the tensile and bond properties of these materials, as well as the overall behaviour of strengthened members. A Round Robin Test was organized by Rilem TC 250-CSM on 28 FRCM composites comprising basalt, carbon, glass, PBO, aramid and steel textiles, embedded in either cement, lime or geopolymer mortars, to collect an experimental dataset and define test protocols. This paper collects the outcomes of this study to highlight fundamental properties of FRCM and to investiga…
Constitutive Numerical Model of FRCM Strips Under Traction
2020
In this paper, the tensile behavior of Fiber Reinforced Cementitious Matrix (FRCM) strips is investigated through Finite Element (FE) models. The most adopted numerical modeling approaches for the simulation of the fiber-matrix interface law are described. Among them, the cohesive model is then used for the generation of FE models which are able to simulate the response under traction of FRCM strips tested in laboratory whose results are available in the technical literature. Tests on basalt, PBO and carbon coated FRCM specimens are taken into account also considering different mechanical ratios of the textile reinforcement. The comparison between FE results and experimental data allows val…
Geometric Analysis of Type B Aortic Dissections Shows Aortic Remodeling After Intervention Using Multilayer Stents
2020
Recently, multilayer stents for type B aortic dissections (TBAD) have been proposed to decrease false lumen flow, increase and streamline true lumen flow, and retain branch vessel patency. We aimed to provide a protocol with standardized techniques to investigate aortic remodeling of TBAD by multilayer flow modulators (MFM) in static geometric and hemodynamic analyses. Combining existing literature and new insights, a standardized protocol was designed. Using pre- and postoperative CT scans, geometric models were constructed, lumen dimensions were calculated, computational fluid dynamics (CFD) models were composed, and velocity and pressures were calculated. Sixteen TBAD cases treated with …
Comparison of resistance to damage of unalloyed carbon steels under the influence of hydrogen
2018
One of the most commonly used construction material in industry is unalloyed steel S235 and S355. These types of steel are used for construction of ships, bridges, coastal construction, welded tanks, and in buildings. Due to the operating conditions, these types of steel may undergo hydrogen degradation in the process of manufacturing of welded structures or when operating the structures. This paper presents the results of study into resistance of selected types of non-alloy structural steels to hydrogen degradation. Tests were carried out to determine changes in mechanical properties in the static trials of stretching without hydrogen, and after saturation with hydrogen. Parallel fractogra…
Effect of Hydrogen and Absence of Passive Layer on Corrosive Properties of Aluminum Alloys
2020
This paper reports the results of research on the effect of hydrogen permeation and the absence of passive layers on the variations in the corrosive properties of aluminum alloys. The study demonstrated that such variations contribute to the deterioration of corrosive properties, which in turn contributes to shortening the reliability time associated with the operation of aluminum alloy structures. The analysis involved structural aluminum alloys: EN AW-1050A, EN AW-5754, and EN AW-6060. It was demonstrated that the absorption of hydrogen by the analyzed alloys led to the shift of the electrode potential to the negative side. The built hydrogen corrosion cells demonstrate in each case the f…
Efficiency of Stress-Strain Models of Confined Concrete With and Without Steel Jacketing to Reproduce Experimental Results
2016
The improvement and the capacity assessment of existing buildings has become the main topic of the last years so that different studies can be found devoted to damaged structures or structures not having a capacity compatible with the safety levels of the actual codes. Reinforced concrete framed structure buildings represent a conspicuous rate of the existing constructions so many efforts are addressed to them. Referring to this type of buildings, a good prediction of strength and deformation capacity requests models able to interpret the constitutive law of concrete confined by internal reinforcement or by eventual external reinforcement applied to increase capacity of cross-sections. Cons…