An-Najah Staff

This study evaluates the adequacy of different methodologies to predict the plastic capacity and response caused by non-uniform thermal gradients through the depth of beam–columns that are loaded only axially at the centroid. Three models with different levels of complexity were used to evaluate the fire response of beam–columns under non-uniform temperature gradients: (1) code-based equations; (2) a fiber-beam element model; and (3) a shell element model that discretizes the full cross section and length and is capable of capturing local (i.e. plate) instability. The code-based equations do not predict the response satisfactorily since these equations do not properly consider temperature gradients. The fiber-beam element and shell model results correlate well to the thermal and structural response of the beam–columns tested experimentally with varying parameters. If local buckling is not expected at ambient temperature, complex shell elements are not necessary when the failure mode is fully plastic and fiber-beam elements, which are simpler and less “computationally expensive” than shells, suffice. The experiments and models also validated equations that consider thermal gradients and predict the plastic capacity and structural response of these members, which includes a moment reversal due to a shift in the section center of stiffness with increasing temperatures.

The behaviour of C-steel in molar hydrochloric acid solution in the presence of Extract (CAE) was investigated using weight loss measurements, potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results obtained reveal that the aggressiveness of hydrochloric solution was considerably decreased in the presence of the CAE. The inhibition efficiency was found to increase with increase in the concentration of the natural substances tested. Potentiodynamic polarization studies clearly reveal that the presence of CAE does not change the mechanism of the hydrogen evolution reaction and they act essentially as cathodic inhibitors. The temperature effect on the corrosion behaviour of C-steel is studied in the range from 298 to 328K without and with at 0.1 g/l. The adsorption isotherm of natural product on the steel has been determined. The apparent activation energies, enthalpies and entropies of the dissolution process were discussed.

A new corrosion inhibitor, namely diethyl 2-(2-oxop yrrolidin-1-yl) ethyl phosphonate (P1) was synthesized and its action on the corrosion of stee l in 0.5 M H 2 SO 4 solution has been studied. Weight loss measurements, potentiodynamic polarisat ion and linear polarisation resistance (Rp) and impedance spectroscopy (EIS) methods have been used. The inhibition efficiency increases with the concentration of P1 to attain 86% at 5.10 -3 M. We have noted a good agreement between gravimetric and electrochemical methods (po tentiodynamic and Rp polarisation and impedance spectroscopy (EIS)). Polarisation measure ments show also that the pyrrolidone derivative acts essentially as a cathodic inhibitor . The cathodic curves indicate that the reduction of proton at the steel surface is an acti vating mechanism. P1 adsorbs on the steel surface according to Langmuir adsorption model. Eff ect of temperature is also studied in the 298-353 K range.

A new corrosion inhibitor, namely diethyl 2-(2-oxop yrrolidin-1-yl) ethyl phosphonate (P1) was synthesized and its action on the corrosion of stee l in 0.5 M H 2 SO 4 solution has been studied. Weight loss measurements, potentiodynamic polarisat ion and linear polarisation resistance (Rp) and impedance spectroscopy (EIS) methods have been used. The inhibition efficiency increases with the concentration of P1 to attain 86% at 5.10 -3 M. We have noted a good agreement between gravimetric and electrochemical methods (po tentiodynamic and Rp polarisation and impedance spectroscopy (EIS)). Polarisation measure ments show also that the pyrrolidone derivative acts essentially as a cathodic inhibitor . The cathodic curves indicate that the reduction of proton at the steel surface is an acti vating mechanism. P1 adsorbs on the steel surface according to Langmuir adsorption model. Eff ect of temperature is also studied in the 298-353 K range

Fire tests were performed to investigate the mechanics and capacity of steel beam–columns that develop a thermal gradient through their depth when exposed to fire. Wide-flanged specimens were loaded axially and tested vertically in a furnace recently commissioned at Michigan State University. The placement of insulation simulated a realistic three-sided heating scenario such as that experienced by a column on the perimeter of a building frame. Specimens were tested with several combinations of load level, fire scenario, and direction of the thermal gradient (which dictates the direction of bending). The different combinations of tested parameters had a significant influence on the fire response of these columns, which all failed by full section yielding due to a combination of axial load (P)(P) and moment (M)(M). These columns developed bending moments in response to through-depth thermal gradients as well as a moment reversal due to a shift in the section’s center of stiffness. The plastic resistance to combinations of axial load and moment was also affected by the thermal gradients such that the critical section, located in the hottest region along the column length, was where moment was the smallest (not the largest, as would be intuitively expected). The experiments and computer models showed good agreement with the predicted demands (i.e. bending moment reversal) and capacity (i.e. changes in the plastic P–MP–M capacity).

The antifungal activity of different extracts of Astericus Imbricatus against botrytis cinerea isolated from tomato show that the percentage of the inhibition was almost100% for the four extracts of organic solvents at 500 ppm. At 250 ppm the percentage of inhibition was almost 70% for the ether extract and for the chloroform extract, 60 % and 50% for the ethyl acetate extract and for methanol extract, respectively. While the aqueous extract of Astericus Imbricatus exhibited moderate antifungal activity. The corrosion inhibition by an Astericus Imbricatus extract (AIE) on C38 steel in hydrochloric acid (HCl) solution has been investigated by electrochemical methods and weight loss. Potentiodynamic polarization studies clearly reveal that the presence of AIE does not change the mechanism of the hydrogen evolution reaction and they act essentially as cathodic and anodic inhibitor. Inhibition efficiency of AIE reached 96.33% at 0.6 g/l. The adsorption of AIE on C38 steel surface obeys the Langmuir isotherm.

Corrosion inhibition efficiencies of 1,4-dihydroquinoxaline-2,3-dione (Q1) and 2-phenylthieno[2,3-b]quinoxaline (Q2) as corrosion inhibitors against the corrosion of steel surface in hydrochloric acid is studied by means of density functional approach B3LYP/6-31G calculations. Quantum chemical parameters such as highest occupied molecular orbital energy (E HOMO), lowest unoccupied molecular orbital energy (E LUMO), energy gap (ΔE), dipole moment (μ), electronegativity (χ), electron affinity (A), global hardness (η), softness (σ), ionization potential (I), the fraction of electrons transferred (∆N), the global electrophilicity ω, and the total energy were calculated. All calculations have been performed by considering density functional theory using the GAUSSIAN03W suite of programs.