Fatigue behavior of damaged concrete beams repaired with composite material

By the present paper, an analytical model was developed to study the cracked FRP-strengthened reinforced concrete beams subjected to fatigue loading. In order to follow the distribution of interfacial shear stresses causing the debonding phenomenon, a new analytical model based on the cohesive zone (CZ) approach was developed. The present model has the possibility to describe the evolution of the shear stress in the three zones (elastic, microcrack and debonding) and the bearing capacity of the repaired structure. Interface damage scenarios were evaluated for a fatigue load estimated to 90% of the elastic load and another at 60% of the ultimate load Pu.  Results obtained are in good agreement with those given by the literature. The results showed that the shear strength developed by the repaired beam is sensitive to the variation of the mechanical properties (Concrete, FRP and Adhesive layer), the fatigue load ratio and the number of cycles. These parameters can be considered as indicators of damage affecting the health status of the structure repaired during fatigue. The debonding at the FRP-concrete interface noticeably reduced the strength and lifespan of the repaired structure.&nbsp

Novel thiophene symmetrical Schiff base compounds as corrosion inhibitor for mild steel in acidic media

The inhibiting effect of two Schiff bases on the corrosion of the mild steel (MS) in 1 M HCl has been studied by electrochemical impedance spectroscopy (EIS) and Tafel polarisation measurements. The Schiff bases, 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ether (L1) and 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ethane (L2), were synthesized using 3-carboxaldehydethiophene and its corresponding amine. Polarisation curves reveal that both compounds are mixed type (cathodic/anodic) inhibitors and inhibition efficiency (% IE) increases with increasing concentration of compounds. It is suggested that their effects depend on their concentrations and the molecular structures. Adsorption of compounds on mild steel surface is spontaneous and obeys Langmuir’s isotherm

Evolution du Facteur de résistance hygrothermique transitoire en fonction des séquences d'empilement pour des composites stratifiés sous des conditions d'environnement cycliques

Exposé à des conditions d'environnement cycliques, les composites à matrices polymères sont capables d'absorber une quantité d'humidité durant de longues années de service. Suite à ce type d'environnement, il se développe des contraintes hygrothermiques extrêmement critiques aux bords et aux interfaces fibres/résines. Au cours des premiers temps de la diffusion d'humidité, les contraintes hygrothermiques sont assez importantes dans la direction transversale, où elles peuvent engendrées un délaminage par gonflement entre les plis formants le stratifié. Pour avoir une idée sur la probabilité d'endommagement des plaques stratifiées sous des contraintes hygrothermiques transitoires, on a adopté le critère de rupture de Tsai-Wu. Le critère de sécurité sera vérifier en évaluant le facteur de résistance (R) pour chaque séquence d'empilement aux bords de la plaque stratifiée

The dynamic interrelationship between interest rate and macroeconomic policy objectives: case of the United Kingdom

The objective of this study is to provide empirical evidence on the short-and long-run relationships between the short-term interest rate, London interbank offered rate (LIBOR) and macroeconomic policy objectives, such as price stability, economic growth,and stability of the exchange rate market. For this purpose, we deploy quarterly frequency data from the United Kingdom between 2000 and 2015 and adopt a multiple regression model. Furthermore, this study uses the Johansen, Stock-Watson cointegration testand the Granger Causality test in order to examine the dynamic short-and long-run relationships among LIBOR, the consumer price index as a proxy of price stability, the real gross domestic product as a proxy of economic growth, and the exchange rate as aproxy of exchange rate market stability.The results showed that all variables have the same order of integration and long-run equilibrium relationships exist between them. The results show evidence of long-run equilibrium relationship between the variables with strong evidence of unidirectional granger causality flow from GDP, CPI and exchange rates to LIBOR. The recommendations proposed in this study have important policy implications for the U.K. government. It is therefore recommended that policy makers and government authorities together withthe Bank of England develop and pursue sensible fiscal and monetary policies that would aim at stabilizing both the micro-and macroeconomic indicators such as the inflation rate, interest rate, exchange rate, and money supply, to enhance the growth of the economy, especially for the period after the BREXIT decision

Production and partial characterization of chitinase from a halotolerant Planococcus rifitoensis strain M2-26

peer reviewedThis paper is the first to investigate the production and partial characterization of the chitinase enzyme from a moderately halophilic bacterium Planococcus rifitoensis strain M2-26, earlier isolated from a shallow salt lake in Tunisia. The impact of salt, salinity concentration, pH, carbon and nitrogen sources on chitinase production and activity have been determined. This is the first report on a high salt-tolerant chitinase from P. rifitoensis, since it was active at high salinity (from 5 to 30% NaCl) as well as in the absence of salt. This enzyme showed optimal activity at 70 C and retained up to 82 and 66% of its original activity at 80 or 90 C, respectively. The activity of the enzyme was also shown over a wide pH range (from 5 to 11). For characterization of the enzyme activity, the chitinase secreted in the culture supernatant was partially purified. The preliminary study of the concentrated dialysed supernatant on native PAGE showed at least three chitinases produced by strain M2-26, with highest activity approximately at 65 kDa. Thus, the thermo-tolerant and high salt-tolerant chitinases produced by P. rifitoensis strain M2-26 could be useful for application in diverse areas such as biotechnology and agro-industry