Search results for "slip"
showing 10 items of 471 documents
Analytical modelling of force transmission in axially loaded RC columns with indirectly loaded jackets
2019
Abstract Concrete and steel jacketing are common strengthening techniques for reinforced concrete (RC) columns subjected to axial loads. In the most of cases the external jacket is made leaving gaps between the strengthening layer and the slabs, avoiding to carry directly a portion of the load. In this way, the external jacket induces a confinement pressure on the inner column, and its beneficial effect is due to the increase of strength and ductility. However, shear stresses develop on the interface between the column and consequently, the external jacket can be considered indirectly loaded. It sustains a portion of the axial load, which depends by the value of the axial shortening, relati…
Simple Plastic Model for Shear Critical SFRC Beams
2010
A simple physical model, for prediction of ultimate shear strength of steel fiber reinforced concrete (SFRC) beams is developed on the basis of a plastic approach originally proposed for reinforced concrete (RC) beams without stirrups. It is founded on the hypothesis that cracks can be transformed into yield lines, and thus is know as Crack Sliding Model (CSM). First, the CSM is improved in order to take into account the shear strength increase for deep beams, due to the arch effect. Then, the effectiveness factors for fibrous concrete under biaxial stresses are evaluated, taking into account the post-cracking tensile strength of SFRC and its ability to control slippage along shear cracks. …
Analytical Prediction of the Flexural Response of External RC Joints with Smooth Rebars
2018
Nel presente lavoro viene presentato un modello analitico in forma chiusa in grado di riprodurre la risposta flessionale monotonica di nodi esterni trave-colonna in c.a. con armature lisce. La colonna viene sottoposta a carico verti-cale costante e la trave ad una forza laterale crescente monotonicamente applicata all’estremità. Il modello si basa sul comportamen-to flessionale di trave e colonna adottando un modello di cerniera plasticità concentrata che include lo scorrimento delle armature della trave. Si assume un dominio sforzo normale-momento bilineare semplificato da cui viene derivato il momento ultimo associato alla forza assiale di progetto. Per il nodo viene adottato un modello c…
Microstructural and tribological study of Nd:YAG laser treated titanium plates.
2008
Abstract In this work, the fretting behaviour of pure Ti plates laser treated with a Nd:YAG pulsed laser was compared to that of untreated Ti plates. Fretting tests were done at room temperature without lubrication. The contact geometry was a cylinder (bearing steel) on a plane. The evolution of both the ratio, μ = Q / P , between the normal and the tangential forces, and the Fouvry's energy criterion ( A ) were recorded as a function of the number of fretting cycles, N . Energy dispersive spectrometry and micro-Raman spectroscopy were used to analyse the fretting scars. The oxidized layer formed by the laser treatment displayed a mixed slip regime as a function of N , and a smaller frettin…
Numerical Modeling Approaches of FRCMs/SRG Confined Masonry Columns
2019
The Fabric Reinforced Cementitious Matrices (FRCMs) and Steel Reinforced Grout (SRG) are a promising strengthening solution for existing masonry since inorganic matrix is considerably compatible with historical substrates. The present paper is focused on a Finite Element (FE) analysis of masonry columns confined with FRCM composites developed by Abaqus-code. The masonry columns were modelled using a macro model approach. The model was performed by using the following functions Concrete Damage Plasticity (CDP) and the Plastic (P) in order to describe the constitutive laws of material for masonry columns and external reinforcement, respectively. Typical failures of FRCM-systems are slippage o…
Stick-slip and convergence of feedback-controlled systems with Coulomb friction
2020
An analysis of stick-slip behavior and convergence of trajectories in the feedback-controlled motion systems with discontinuous Coulomb friction is provided. A closed-form parameter-dependent stiction region, around an invariant equilibrium set, is proved to be always reachable and globally attractive. It is shown that only asymptotic convergence can be achieved, with at least one but mostly an infinite number of consecutive stick-slip cycles, independent of the initial conditions. Theoretical developments are supported by a number of numerical results with dedicated convergence examples.
Polyelectrolyte Electrophoresis in Nanochannels: A Dissipative Particle Dynamics Simulation
2010
We present mesoscopic DPD-simulations of polyelectrolyte electrophoresis in confined nanogeometries, for varying salt concentration and surface slip conditions. Special attention is given to the influence of electroosmotic flow (EOF) on the migration of the polyelectrolyte. The effective polyelectrolyte mobility is found to depend strongly on the boundary properties, i.e., the slip length and the width of the electric double layer. Analytic expressions for the electroosmotic mobility and the total mobility are derived which are in good agreement with the numerical results. The relevant quantity characterizing the effect of slippage is found to be the dimensionless quantity $\kappa \: \delta…
Positron Annihilation in Metals Defected by Action of the Tensile Force
2006
Results of experimental investigations of uniaxially elongated mono- and polycrystalline samples of several metals (Fe, Ta, Pd, Ag, and Au), performed using the positron annihilation methods, are reviewed. The dependences of the S-parameters and positron lifetimes on the relative elongation of the samples were presented. The data obtained for polycrystalline samples indicate that in the proportionality and limited proportionality regions the changes in the physical properties are governed mainly by generation of vacancies and by kinetics of formation and transformations of vacancy clusters occurring flrst of all on the grain boundaries of monocrystallites. In the region of plastic deformati…
Right-turn Bypass Lanes at Roundabouts: Geometric Schemes and Functional Analysis
2012
Right-turn bypass lanes can be implemented in conventional and innovative roundabout intersections to increase the capacity and improve the global functional performances. The Right-turn bypass lanes (also called slip lanes) can be distinguished according to the planimetric layout and the entry control type (stop, yield slip or Free Flow acceleration lane). This paper presents a closed-form model for the estimation of capacity, delays and level of service of roundabout equipped with Right-turn bypass lanes, considering the effect of geometric slip lane schemes, control type, vehicular and pedestrian flow. In order to examine the traffic conditions which can benefit from slip lane roundabout…
Capillary Rise in Nanopores: Molecular Dynamics Evidence for the Lucas-Washburn Equation
2007
When a capillary is inserted into a liquid, the liquid will rapidly flow into it. This phenomenon, well studied and understood on the macroscale, is investigated by Molecular Dynamics simulations for coarse-grained models of nanotubes. Both a simple Lennard-Jones fluid and a model for a polymer melt are considered. In both cases after a transient period (of a few nanoseconds) the meniscus rises according to a $\sqrt{\textrm{time}}$-law. For the polymer melt, however, we find that the capillary flow exhibits a slip length $\delta$, comparable in size with the nanotube radius $R$. We show that a consistent description of the imbibition process in nanotubes is only possible upon modification o…