An experimental and numerical investigation on the effect of longitudinal reinforcements in torsional resistance of RC beams

A.H. Khagehhosseini,R. Porhosseini,R. Morshed,A. Eslami 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.2

It is evident that torsional resistance of a reinforced concrete (RC) member is attributed to both concrete and steel reinforcement. However, recent structural design codes neglect the contribution of concrete because of cracking. This paper reports on the results of an experimental and numerical investigation into the torsional capacity of concrete beams reinforced only by longitudinal rebars without transverse reinforcement. The experimental investigation involves six specimens tested under pure torsion. Each specimen was made using a cast-in-place concrete with different amounts of longitudinal reinforcements. To create the torsional moment, an eccentric load was applied at the end of the beam whereas the other end was fixed against twist, vertical, and transverse displacement. The experimental results were also compared with the results obtained from the nonlinear finite element analysis performed in ANSYS. The outcomes showed a good agreement between experimental and numerical investigation, indicating the capability of numerical analysis in predicting the torsional capacity of RC beams. Both experimental and numerical results showed a considerable torsional post-cracking resistance in high twist angle in test specimen. This post-cracking resistance is neglected in torsional design of RC members. This strength could be considered in the design of RC members subjected to torsion forces, leading to a more economical and precise design.

An Isothermal Titration Microcalorimetric Study on the Interaction ofThree Water-Soluble Porphyrins with Histone H2B

A.K.Bordbar,A.R.Ghaderi,E.Safaei,S.Tangestaninejad,A.Eslami,A.A.Saboury,A.A.Moosavi-Movahedi 대한화학회 2003 Bulletin of the Korean Chemical Society Vol.24 No.5

An experimental and numerical investigation on the effect of longitudinal reinforcements in torsional resistance of RC beams

Khagehhosseini, A.H.,Porhosseini, R.,Morshed, R.,Eslami, A. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.2

It is evident that torsional resistance of a reinforced concrete (RC) member is attributed to both concrete and steel reinforcement. However, recent structural design codes neglect the contribution of concrete because of cracking. This paper reports on the results of an experimental and numerical investigation into the torsional capacity of concrete beams reinforced only by longitudinal rebars without transverse reinforcement. The experimental investigation involves six specimens tested under pure torsion. Each specimen was made using a cast-in-place concrete with different amounts of longitudinal reinforcements. To create the torsional moment, an eccentric load was applied at the end of the beam whereas the other end was fixed against twist, vertical, and transverse displacement. The experimental results were also compared with the results obtained from the nonlinear finite element analysis performed in ANSYS. The outcomes showed a good agreement between experimental and numerical investigation, indicating the capability of numerical analysis in predicting the torsional capacity of RC beams. Both experimental and numerical results showed a considerable torsional post-cracking resistance in high twist angle in test specimen. This post-cracking resistance is neglected in torsional design of RC members. This strength could be considered in the design of RC members subjected to torsion forces, leading to a more economical and precise design.

An Isothermal Titration Microcalorimetric Study on the Interaction of Three Water-Soluble Porphyrins with Histone H₂B

Bordbar, A.K.,Ghaderi, A.R.,Safaei, E.,Tangestaninejad, S.,Eslami, A.,Saboury, A.A.,Moosavi Movahedi, A.A. Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.5

In the present work, the interaction of three water soluble porphyrins, tetra(p-trimethyle) ammonium phenyl porphyrin iodide (TAPP) as a cationic porphyrin, tetra sodium meso-tetrakis (p-sulphonato phenyle) porphyrin (TSPP) as an anionic porphyrin and manganese tetrakis (p-sulphonato phenyl) porphinato acetate (MnTSPP) as a metal porphyrin, with histone H₂B have been studied by isothermal titration microcalorimetry at 8 mM phosphate buffer, pH 6.8 and 27 °C. The values of binding constant, entropy, enthalpy and Gibbs free energy changes for binding of the first MnTSPP, and first and second TSPP and TAPP molecules were estimated from microcalorimetric data analysis. The results represent that the process is both entropy and enthalpy driven and histone induces self-aggregation of the porphyrins. The results indicate that both columbic and hydrophobic interactions act as self-aggregation driving forces for the formation of aggregates around histone.

Electrochemical and quantum chemical study of Thiazolo-pyrimidine derivatives as corrosion inhibitors on mild steel in 1 M H2SO4

S. Hejazi,Sh. Mohajernia,M.H. Moayed,A. Davoodi,M. Rahimizadeh,M. Momeni,A. Eslami,A. Shiri,A. Kosari 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.25 No.-

Inhibitive performance of a new thiazolo-pyrimidine derivative has been investigated on mild steel in a solution of 1 M H2SO4. Electrochemical measurement, scanning electron microscope analysis and quantum chemical calculations are the tests and methods used to assess the performance of the inhibitors. The results indicate that the thiazolo-pyrimidine derivative used acts as a mixed-type inhibitor retarding the anodic and cathodic corrosion reactions. The studied compounds followed the Langmuir adsorption isotherm. Thermodynamic parameters showed that inhibitor adsorption is physical as determined by those parameters. The effect of molecular structure on the inhibition efficiency was investigated by quantum chemical calculations.

A parametric investigation on the hysteretic behaviour of CFT column to steel beam connections

R. Esfandyary,M.S. Razzaghi,A. Eslami 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1

The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic loaddisplacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.

Effect of Shape Memory Alloy Wires on the Buckling Behavior of Fiber Metal Laminates

R. Eslami-Farsani,M. R. Mohaseb Karimlou,A. Saeedi,A. Zamani 한국섬유공학회 2019 Fibers and polymers Vol.20 No.8

Buckling behavior of shape memory alloy (SMA) reinforced fiber metal laminates (FML) was experimentallyinvestigated. The SMA reinforced FML specimens with three different pre-strain levels (1, 2 and 3 %) and different numberof the embedded wires (2, 4 and 6 wires) were prepared by a specific mold and hydraulic pressure. The effects of the appliedpre-strains in the SMA wires, as well as the stacking sequence of the laminate, SMA volume fraction and the location of thewires were studied on the axial and lateral force-displacement diagrams for the specimens during buckling tests. According tothe results, 53 % enhancement in the buckling load was obtained for 2 SMA wires reinforced FML specimens in comparisonwith the specimens without embedded SMA wires. In constant volume fraction of the SMA, pre-straining the wires by 3 %led to 25 % improvement in the buckling load, in comparison with the specimens reinforced with 1 % pre-strained wires. Theinfluence of the FML stacking sequence on the results was also discussed.

Exact solution for asymmetric transient thermal and mechanical stresses in FGM hollow cylinders with heat source

M. Jabbari,A.R. Vaghari,A. Bahtui,M.R. Eslami 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.5

Transient solution of asymmetric mechanical and thermal stresses for hollow cylinders made of functionally graded material is presented. Temperature distribution, as function of radial and circumferential directions and time, is analytically obtained, using the method of separation of variables and generalized Bessel function. A direct method is used to solve the Navier equations, using the Euler equation and complex Fourier series.

Experimental investigation on optimal shear strengthening of RC beams using NSM GFRP bars

M. Ramezanpour,R. Morshed,A. Eslami 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.1

Several techniques have been developed for shear strengthening of reinforced concrete (RC) members by using fiber reinforced polymer (FRP) composites. However, debonding of FRP retrofits from concrete substrate still deemed as a challenging concern in their application which needs to be scrutinized in details. As a result, this paper reports on the results of an experimental investigation on shear strengthening of RC beams using near surface mounted (NSM) FRP reinforcing bars. The main objective of the experimentation was increasing the efficiency of shear retrofits by precluding/postponing the premature debonding failure. The experimental program was comprised of six shear deficient RC beams. The test parameters include the FRP rebar spacing, inclination angle, and groove shape. Also, an innovative modification was introduced to the conventional NSM technique and its efficiency was evaluated by experimental observation and measurement. The results testified the efficiency of glass FRP (GFRP) rebars in increasing the shear strength of the test specimens retrofitted using conventional NSM technique. However, debonding of FRP bars impeded exploiting all retrofitting advantages and induced a premature shear failure. On the contrary, application of the proposed modified NSM (MNSM) technique was not only capable of preventing the premature debonding of FRP bars, but also could replace the failure mode of specimen from the brittle shear to a ductile flexural failure which is more desirable.

Experimental investigation on optimal shear strengthening of RC beams using NSM GFRP bars

Ramezanpour, M.,Morshed, R.,Eslami, A. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.1

Several techniques have been developed for shear strengthening of reinforced concrete (RC) members by using fiber reinforced polymer (FRP) composites. However, debonding of FRP retrofits from concrete substrate still deemed as a challenging concern in their application which needs to be scrutinized in details. As a result, this paper reports on the results of an experimental investigation on shear strengthening of RC beams using near surface mounted (NSM) FRP reinforcing bars. The main objective of the experimentation was increasing the efficiency of shear retrofits by precluding/postponing the premature debonding failure. The experimental program was comprised of six shear deficient RC beams. The test parameters include the FRP rebar spacing, inclination angle, and groove shape. Also, an innovative modification was introduced to the conventional NSM technique and its efficiency was evaluated by experimental observation and measurement. The results testified the efficiency of glass FRP (GFRP) rebars in increasing the shear strength of the test specimens retrofitted using conventional NSM technique. However, debonding of FRP bars impeded exploiting all retrofitting advantages and induced a premature shear failure. On the contrary, application of the proposed modified NSM (MNSM) technique was not only capable of preventing the premature debonding of FRP bars, but also could replace the failure mode of specimen from the brittle shear to a ductile flexural failure which is more desirable.