Transverse Vibration Analysis of Uniform Beams under Various Ends Restraints

AbstractThe beam analysis, based on the assumptions of the Bernoulli-Euler theory, in free vibration has been largely investigated. Many researches focused on the transverse vibrations study, under the application of different boundary constraints where different theories were applied. The considered stiffness and mass matrices are those obtained by assembling the elementary ones resulting from the FEM use The Jacobi method allowed the solution of the eigenvalue problem. These well known concepts were applied to the study of beams with constant geometrical and mechanical characteristics having one to two overhangs with variable lengths. Murphy studied, by an algebraic solving approach, a simply supported beam with two overhangs of arbitrary length, which allows an experimental determination of the E elastic modulus.The advantage of our paper offers a possibility of extending this approach to many interesting problems formed by beams vibrating transversally with various ends restraints

Permeability of High-Performance Fiber Reinforced Concrete Immersed in High Concentration Sodium Chloride Solution

This paper aims to study the permeability of High-Performance Concrete containing natural pozzolan and reinforced with fibers in high concentration sodium chloride solution. Optimized finely ground natural pozzolan was employed as 6% of partial substitution of the cement. Polypropylene fibers with 6 mm and 12 mm lengths were introduced individually for a volume fraction of 0.1% and 0.15% respectively. Then, in combination with a total fiber content of 0.25%. The effect of sodium chloride attack on the performance of concretes was assessed through the measurement of the compressive strength, splitting tensile strength, sorptivity, rapid chloride permeability test, apparent and intrinsic gas permeability, and visual inspection at various testing ages (28, 90, 180, and 365 days). A total of four (04) types of concretes were cast: one (01) High-Performance Concrete (HPC), and three (03) High-Performance Fiber Reinforced Concrete (HPFRC) stored in tap water and sodium chloride environment. From the experiments performed, it can be concluded that the polypropylene fibers introduction into HPC favorably affect its chemical resistance to chloride attack and long-term durability. The difference in the permeability of HPC and HPFRC stored in tap water and chloride environment is not significant. Furthermore, the visual investigation of HPFRC after 365 days of immersion in sodium chloride environment showed no sign of degradation. Based on the results obtained in this study, we recommend the use of hybrid fiber-reinforced concrete (F0-0.25%) as a low permeable material in a severe chloride environment

Experimental Study of Concrete Class Influence on Cracks Openings

The aim of this experimental work is to study reinforced concrete continuous beams cracking by considering different classes of concretes. As it is well known, the design of reinforced concrete structures considers three limit states (limit state of collapse, limit state of strain and limit state of cracking). The cracks in reinforced concrete structures are admitted in the phase II (cracked sections). Thus, the phenomenon of cracks can be treated as a normal state only when the cracks opening is limited to avoid a permanent risk of collapse and ensure durability for the civil engineering constructions. Tests on real scale reinforced concrete continuous beams were carried out under concentrated loads increasing from zero up to collapse. The influence of the concrete classes on crack opening has been investigated

Site-specific and synergistic stimulation of methylation on the bacterial chemotaxis receptor Tsr by serine and CheW

BACKGROUND: Specific glutamates in the methyl-accepting chemotaxis proteins (MCPs) of Escherichia coli are modified during sensory adaptation. Attractants that bind to MCPs are known to increase the rate of receptor modification, as with serine and the serine receptor (Tsr), which contributes to an increase in the steady-state (adapted) methylation level. However, MCPs form ternary complexes with two cytoplasmic signaling proteins, the kinase (CheA) and an adaptor protein (CheW), but their influences on receptor methylation are unknown. Here, the influence of CheW on the rate of Tsr methylation has been studied to identify contributions to the process of adaptation. RESULTS: Methyl group incorporation was measured in a series of membrane samples in which the Tsr molecules were engineered to have one available methyl-accepting glutamate residue (297, 304, 311 or 493). The relative rates at these sites (0.14, 0.05, 0.05 and 1, respectively) differed from those found previously for the aspartate receptor (Tar), which was in part due to sequence differences between Tar and Tsr near site four. The addition of CheW generated unexpectedly large and site-specific rate increases, equal to or larger than the increases produced by serine. The increases produced by serine and CheW (added separately) were the largest at site one, ~3 and 6-fold, respectively, and the least at site four, no change and ~2-fold, respectively. The rate increases were even larger when serine and CheW were added together, larger than the sums of the increases produced by serine and CheW added separately (except site four). This resulted in substantially larger serine-stimulated increases when CheW was present. Also, CheW enhanced methylation rates when either two or all four sites were available. CONCLUSION: The increase in the rate of receptor methylation upon CheW binding contributes significantly to the ligand specificity and kinetics of sensory adaptation. The synergistic effect of serine and CheW binding to Tsr is attributed to distinct influences on receptor structure; changes in the conformation of the Tsr dimer induced by serine binding improve methylation efficiency, and CheW binding changes the arrangement among Tsr dimers, which increases access to methylation sites

corpus (linguistique) et cartographie : l’interprétation de certains phénomènes de variation régionale (à «Tizi-Ouzou»)

Il s'agit, dans cet article, d'enregistrer diverses réalisations (suivant une grille d’enquête / liste de mots par exemple) dans quelques parlers régionaux de la Kabylophonie (ceux de la wilaya de Tizi-Ouzou), de les répertorier et de créer des cartes géolinguistiques pour les représenter et essayer de les interpréter/classifier.Ce travail portera sur le "corpus" (corpus linguistique / grille d’enquête ou questionnaire portant sur certains phénomènes linguistiques), la cartographie (reporter les diverses réalisations sur des cartes géolinguistiques) et l’interprétation des résultats en se référant aux travaux antérieurs (l’hypothèse avancée par Kamal Nait-Zerrad (2004, …) concernant la classification des parlers kabyles en quatre [4] groupes «plus ou moins» homogènes par exemple)

Note sur le schwa dans le système de notation usuelle du kabyle

Cette contribution se propose de (re)voir le "statut" du schwa1 dans la notation usuelle du kabyle (écriture kabyle).Nous allons essayer à travers ce travail de répondre à certaines questions qui tournent autour de l‟utilité de représenter graphiquement le schwa en notation usuelle de la langue kabyle

"L’enseignement de la langue «berbère» en Algérie: de 1995 à 2011"

Mon intervention se propose de donner un aperçu sur les droitsculturels et linguistiques des minorités berbérophones en Algérie à travers le cas de l’enseignement de "tamazight/berbère" [les langues berbères] dans ces régions et plus particulièrement en Kabylie

Compatibility of Slag-Blended Cement with Polycarboxylate Ether Superplasticisers: Rheological Properties Study

The compatibility of slag blended-cement (SBC) with superplasticisers was investigated using rheological measurements. Accordingly, continuous flow tests and thixotropic behaviors were studied  for different ages of hydration. In this work, the slag was used in the range of 0-40% in order to substitute the ordinary Portland cement (OPC). Two polycarboxylates ether superplasticisers (PCEs) were used, the acrylic copolymer (PA) and modified polycarboxylate (PC). The saturation point of each superplasticiser was determined on pastes by rheological tests, it is 2% on amount of cement, and the water/cement report is equal to 0.35. The investigation was carried out using a rotational rheometer AR2000 with coaxial cylinders’ geometry. The results showed that the PC-admixture is more efficient than the PA-admixture in OPC; the consistence was consecutively 4.75 Pa.s and 10.45 Pa.s. In addition, the fluidizing effect of the admixtures on cement pastes is conditioned by the presence of slag. The use of PA-admixture in SBC improved rheological properties. However, the use of PC-admixture in SBC increased greatly the viscosity, which involves an incompatibility, the thixotropy increment was from 46898.9 Pa/s (F4) to 59690.1 Pa/s (F9)

Local Ductility and Global Behavior Factor of Steel Frame Structures Braced by Centered Bars System

When an earthquake occurs, civil engineering structures are subjected to forces that lead to a non linear behavior. This is often the case for designed steel structures. So, they absorb a larger part of the seismic energy transmitted to its resistant elements (columns and diagonals). This ability to dissipate energy through plastic deformation is expressed by the q behavior factor, used in the seismic design codes. In this paper a distribution of the local required ductility as a function of the behavior factor is given for steel structures braced by the stability bents of X shape