Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : natural frequencies


ANSYS-Based Structural Analysis Study of Elevated Spherical Tank Exposed to Earthquake

Mahmoud Saleh Al-Khafaji; Ahlam S. Mohammed; Muna A. Salman

Engineering and Technology Journal, 2021, Volume 39, Issue 6, Pages 870-883
DOI: 10.30684/etj.v39i6.460

Damage of elevated tanks during earthquakes can jeopardize the supply of drinking water and causes significant economic losses. Therefore, seismic analysis of tanks containing liquids requires special consideration. Knowledge of liquid hydrodynamic pressures developed during an earthquake is important for tank design. This paper aims to verify the dynamic reaction of structural systems of spherical elevated steel tanks containing water, and determine the natural frequencies that contribute to the physical response, as well as seismic analysis of the tank. A three dimensional Finite Element Model was developed to identify the main parameters involved in this response for three different fullness ratio (0.00%, 53.30% and 71.11%) using the ANSYS software. The model was implemented and validated based on the results of a previously conducted experimental study. Moreover, it was analyzed under the impact of the most severe earthquake that Iraq was exposed to in 2017 with a magnitude of 7.2 on the Richter scale. The results showed a very good agreement in natural frequency with a discrepancy (root mean square error) of 2% (0.05 Hz), 6.9% (0.15 Hz) and 9.5% (0.2 Hz) for the fullness ratio 0%, 53.3% and 71.11%, respectively In addition, the selected element type and the method of analysis are applicable. Moreover, results of displacement and stresses from earthquake analysis indicated that the spherical tank could lose stability in time 1.4 seconds of the proposed time for the worst part of the earthquake, when displacement records highest values in the direction of earthquake for the tank body at chosen points in the top, middle, and bottom of the tank body which were almost equally at all cases proposed in this study.

Behavior of High-Rise Steel Building With The Inclusion of Warping

a H. Shareef; Najla; Haitham H.Muteb; Hisham M. AL-Hassani

Engineering and Technology Journal, 2010, Volume 28, Issue 22, Pages 6580-6601

The mathematical procedure in this study covers the calculation of sectorial
properties of the equivalent cross-sectional storey for high-rise building frames. The
formulation is efficiently used to obtain the free vibration analysis of high-rise
buildings which are constructed from several columns, beams, shear walls and
bracing etc. the analysis is based on transformation the complex system to a simple
tall column to represent a cantilevered tall building structure. This is partitioned to
nodes one of which indicates a storey with equivalent cross-sectional properties for
all storeys' elements after calculation of these properties with respect to the shear
center of high-rise building. A thin walled bar finite element with seven degrees of
freedom at each node is assumed. A new formulation of the stiffness and consistent
mass matrices of the thin- walled element is presented in this study. The effect of
cross sectional warping and its properties on the flexural, torsional and axial
properties was investigated, using discrete element approach in idealizing the
structure in high rise building. For the purpose of the present study, it is assumed
that the cross-sectional types under condition are only of thin-walled sections.
Algorithm method was developed which covers the calculation of sectorial
properties of the cross section for floor plan in high-rise building, to study the share
of columns for lateral shear force resistance, and investigate the behavior of different
types of high-rise building with inclusion of warping restraint. The effect of natural
frequency with height of tall buildings, and the mode shape for different crosssectional
plans of high-rise building was studied. To check the efficiency and
accuracy, the mathematical procedure is demonstrated for static and dynamic
examples by comparing the results with those obtained by using software ANSYS
program. A difference of 15% is shown. An eigen value problem is analyzed and
numerical examples are discussed.