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.

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.

Elasticity solution and free vibrations analysis of laminated anisotropic cylindrical shells

Shakeri, M.,Eslami, M.R.,Yas, M.H. Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.7 No.2

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

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

Jabbari, M.,Vaghari, A.R.,Bahtui, A.,Eslami, M.R. Techno-Press 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.

Elasticity solution of multi-layered shallow cylindrical panels subjected to dynamic loading

M. Shakeri,M. R. Eslami,A. Alibiglu 국제구조공학회 2002 Steel and Composite Structures, An International J Vol.2 No.3

Elasticity solutions to the boundary-value problems of dynamic response under transverse asymmetric load of cross-ply shallow cylindrical panels are presented. The shell panel is simply supported along all four sides and has finite length. The highly coupled partial differential equations are reduced to ordinary differential equations with constant coefficients by means of trigonometric function expansion in the circumferential and axial directions. The resulting ordinary differential equations are solved by Galerkin finite element method. Numerical examples are presented for two (0/90 deg.) and three (0/90/0 deg.) laminations under dynamic loading.

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.

Reflections on the Mobilities, Immobilities, Inequalities, and Traveling Ideas in Qatar

Keith M. Graham,Aymen Elsheikh,Zohreh R. Eslami 아시아영어교육학회 2020 The Journal of Asia TEFL Vol.17 No.2

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.

Investigation of Longitudinal and Transverse Reinforcing Single Lap Joints of the Polymer Composites/Al under Hygrothermal Condition

F. Jafari,R. Eslami-Farsani,S.M.R. Khalili 한국섬유공학회 2020 Fibers and polymers Vol.21 No.10

In this study, the effect of longitudinal and transversal reinforcing of epoxy based carbon fiber reinforcedcomposite/Al (CFRP/Al) and glass fiber reinforced composite/Al (GFRP/Al) single lap joints (SLJs) by using of pins andwires has been investigated under hygrothermal conditions. Overall three sets of specimens for each composite/Al joint weremanufactured which consist of single lap joint (SLJ), single lap joint reinforced with 6 steel pins of 1 mm diameter intransverse direction (SLJP) and single lap joint reinforced with wires of diameter 0.2 mm, in longitudinal direction (SLJW)for CFRP/Al and GFRP/Al adherends. The tensile properties of the samples were measured after 500 and 1000 hrs. inhygrothermal conditions of 70 ºC, relative humidity of 85 % and compared corresponding to unheated samples. The resultsshow that using of pins, increases the tensile strength by 14 % in GFRP/Al and 13.7 % in CFRP/Al SLJs. Also wire increasedthe tensile strength of the SLJs by 26 % in GFRP/Al and 19 % in CFRP/Al SLJs. Hygrothermal conditions decreased thetensile strength of both GFRP/Al and CFRP/Al SLJs samples, where the highest degradation was observed in simple GFRP/Al SLJs (34.45 %) and the lowest was in wire reinforced CFRP/Al SLJs (21 %). Overall it could be concluded that wires andpins increases the lifespan of both CFRP/Al and GFRP/Al SLJs under hygrothermal conditions.