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Showing 3 results for Kazemi

M.e. Torki, M. Taghi Kazemi, S.b. Talaeitaba,
Volume 13, Issue 2 (Transaction A: Civil Engineering June 2015)

The effect of axial deformation of shell particles on the dynamic instability (flutter) of cantilevered cylindrical shells made of functionally graded materials (FGM) under an end axial follower force is addressed. To this end, at first, results for free vibration of FGM cylindrical shells were verified with previous outcomes and they were in very good agreement. Then, the effect of axial deformation of the shell, acting like a reducing linearly-distributed follower load, on the critical circumferential mode number and the flutter load of FGM shells was accounted for. Finally, the effect of axial deformation of the shell particles on the critical circumferential mode number and the flutter load of FGM shells were investigated. In this case, three homogeneous shells with different elasticity moduli and densities and two FGM materials were considered: nickel-stainless steel and stainless steel-alumina. Results include the increasing critical circumferential mode number and the increasing value of the flutter load due to axial deformation. The increase in the flutter load occurs in proportion to the whole elasticity modulus of the material, and thus it can be derived from the formula of mixture for an FGM.

Fatemeh Kazemi, Dr Saeed Reza Khodashenas, Hamed Sarkardeh,
Volume 14, Issue 1 (Transaction A: Civil Engineering 2016)

Stilling basins dissipate energy in order to form hydraulic jumps and rotational flows. Hydraulic jump and rotational current phenomenon produces pressure fluctuation at the bottom of stilling basins. In the present study, pressure fluctuations and their locations have been studied in a physical model of Nimrod Dam. Results showed that fluctuations in presence of jump in the basin are high and therefore the fluctuation factors are respectively high. Regarding available empirical equations, the thickness of slab for different hydraulic conditions were calculated and compared in 1D and 2D conditions. By analyzing collected data, it was observed that, results of 1D were underestimated in comparison by 2D calculations.

Vahid Broujerdian, Mohammad T. Kazemi,
Volume 14, Issue 8 (Transaction A: Civil Engineering 2016)

Complex nature of diagonal tension accompanied by formation of new cracks as well as closing and propagating preexisting cracks has deterred researchers to achieve an analytical and mathematical procedure for accurate predicting shear behavior of reinforced concrete, and there is the lack of a unique theory accepted universally. Shear behavior of reinforced concrete is studied in this paper based on recently developed constitutive laws for normal strength concrete and mild steel bars using nonlinear finite element method. The salient feature of these stress-strain relations is to account the interactive effects of concrete and embedded bars on each other in a smeared rotating crack approach. Implementing the considered constitutive laws into an efficient secant-stiffness based finite element algorithm, a procedure for nonlinear analysis of reinforced concrete is achieved. The resulted procedure is capable of predicting load-deformation behavior, cracking pattern, and failure mode of reinforced concrete. Corroboration with data from shear-critical beam test specimens with a wide range of properties showed the model to predict responses with a good accuracy. The results were also compared with those from the well-known theory of modified compression field and its extension called disturbed stress field model which revealed the present study to provide more accurate predictions. 

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