Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Finite elements


Stress Analysis Around Tunnels During Construction Stages Using Finite Elements Method

Kais T. Shlash; Nahla M. Salim; Zainab H. Shaker

Engineering and Technology Journal, 2014, Volume 32, Issue 6, Pages 1562-1579

In this study, the stresses around a tunnel during construction stages are discussed. For this purpose, the finite element method (FEM) was adopted as an effective approach to analyze the problem using (SIGMA/W) program.
The research includes the study of the behavior of soil due to excavation of tunnel by calculating the displacements and stresses in three positions of tunnel (crown, wall, and invert) during the various stages of construction.
The finite element analyses were carried out using (Elastic- plastic) and (linear elastic) models for the soil and the concrete liner respectively. From the results, it can be noticed that increasing the number of excavation stages (using six stages) decreases the displacement comparing with excavation using one stage.

Development of Three - Layer Composite Steel - Concrete - Steel Beam Element with Applications

Jamal A. Farhan; Hussain M. Hussain

Engineering and Technology Journal, 2010, Volume 28, Issue 24, Pages 6970-6985

In this study, a general linear one-dimensional finite element beam model is developed for the analysis of the three layer composite steel- concrete- steel beams which are a special case of the multi-layer
Connectors, concrete layer thickness, plate thickness, type of loading and concrete compressive strength composite beams. The model is based on partial interaction theory of composite beams where the flexibility of shear connectors is allowed. A program is constructed using VISUAL BASIC language to analyze this type of beams. Numerical applications are presented to demonstrate the validity and applicability of the present method. A parametric study is carried out to demonstrate the effect of some parameters including the variation of shear stiffness of shear on the behaviour of three-layer composite beams. The results of
the proposed programmed model shows a good agreement with those obtained by finite elements method using ANSYS program (Release 11, 2007. The models used in ANSYS program are shell element, brick element and combine element to simulate the behaviour of steel plates, concrete part and shear connectors respectively

Consolidation Characteristics of Unsaturated Soil

Firas J. Kadhim; Mohammed Y. Fattah

Engineering and Technology Journal, 2009, Volume 27, Issue 10, Pages 2027-2046

The most common three-phase problem in porous media is the flow of air and water. This is for example found in the unsaturated zone, where water infiltrates through partly saturated pores to the groundwater. Liquid flow in the unsaturated zone is controlled by a combination of gravitational, capillary, and viscous forces. The mechanical behaviour of partially saturated soils can be very different from that of fully saturated soils. It has long been established that for such soils, changes in suction do not have the same effect as changes in the applied stresses, and consequently the effective stress principle is not applicable. Conventional constitutive models, which are based on this principle, are therefore of limited use when analyzing
geotechnical problems that involve the presence of partially saturated soil zones. In this paper, Al-Mdaina trial embankment was the problem analysed. The finite element programs SIGMA/W and SEEP/W were used, and eight noded isoparametric quadrilateral elements were used for modelling both the soil skeleton and pore water pressure. Parametric study was carried out and different parameters were changed to find their effects on the behaviour of partially saturated soil. The
parameters include the modulus of elasticity and permeability of the soil. It was concluded that the effect of modulus of elasticity on the behaviour of unsaturated soil is apparent at early stages of consolidation and diminishes when the time proceeds. When the clay layer consists of soft clay (Esoil <10000 kN/m2), the effect of unsaturated soil is apparent, while the effect of the modulus of elasticity diminishes when the soil is stiff.

Dynamic Analysis of Al-Adhaim Zoned Earthdam

Mohammed Y. Fattah; Maha H. Nsaif

Engineering and Technology Journal, 2009, Volume 27, Issue 8, Pages 1582-1610

Among external forces, the dam is subjected to earthquakes which are naturally or
artificially occurring and resulting in time-varying deflections, excess pore water pressure
and liquefaction at some zones in the dam.
In this paper, coupled dynamic analysis has been carried out on zoned earthdam
subjected to earthquake excitation in which displacements and pore water pressures are
calculated. The finite element method is used and the computer program QUAKE/W is
adopted for this task.
Al-Adhaim dam which is an earthdam located near the place of intersection of Tuz Jay
and the river Al-Adhaim is used as a case study. A parametric study was carried out to
investigate the effect of the maximum earthquake horizontal acceleration on the general
response of the dam.
It was found that as the maximum horizontal acceleration of the input motion increases,
both horizontal and vertical displacement increase. In all cases, the effect of the input ground
acceleration diminishes at time (60 sec.) from the time of earthquake shock. When the
maximum horizontal acceleration of the input motion increases from (0.05g) to (0.2g), the
horizontal acceleration predicted at a node located at the core base increases by about
(200 %) while the maximum effective stress increases by about (32 %).

Behaviour of Encased Floating Stone Columns

Qutaiba G. Majeed; Mohammed Y. Fattah

Engineering and Technology Journal, 2009, Volume 27, Issue 7, Pages 1404-1421

In this paper, the finite element method is utilized as a tool for carrying out different
analyses of stone column–soil systems under different conditions. A trial is made to
improve the behaviour of stone column by encasing the stone column by geogrid as
reinforcement material .
The program CRISP2D is used in the analysis of problems. The program adopts the
finite element method and allows prediction to be made of soil deformations considering
Mohr–Coulomb failure criterion for elastic-plastic soil behaviour.
A parametric study is carried out to investigate the behaviour of ordinary and
encased floating stone columns in different conditions. Different parameters were studied to
show their effect on the bearing improvement and settlement reduction of the stone column.
These include the length to diameter ratio (L/d), shear strength of the surrounding soil and,
the area replacement ratio (as) and others.
It was found that the important increase in strength of stone column occurs when it
is encased by geogrid for (length/diameter) L/d = 8 while in case of L/d = 4, a slight
increase in the bearing improvement ratio at the early stages of applying the load is
obtained and then the value of (q/Cu) for both ordinary and encased stone columns is the
same.

Numerical Study of Forced Convection in Wavy and Diverged-Converged Ducts

Anmar M. Basheer; Sattar J. Habeeb; Waheed S. Mohamad; Qutaiba G. Majeed; Mohammed Y. Fattah; Jawad K.Oleiwi; Mohammed S. Hamza; Mayyadah Sh. Abed; Amjed J. Hamidi; Ahmed Alaa Ogla; Yaser Nabeel Ibrahem

Engineering and Technology Journal, 2009, Volume 27, Issue 7, Pages 1385-1403

A three-dimensional study of developing fluid flow and heat transfer through
wavy and diverged-converged ducts were studied numerically for a Prandlt number 0.7
and 5.85 and compared with flow through corresponding straight duct. The Navier-
Stokes and energy equations are solved by using control finite volume method.
Development of the Nusselt number in wavy and diverged-converged ducts are
presented for different flow rates (50

Keywords

forced convection
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numerical study
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wavy duct
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diverged-converged duct

Effect Of Soil Consistency On Flow Characteristics Of Acids Through Cohesive Soils

Husam Hikmat Bakir; Falah Hassan Rahil; Mohammed Yousif Fattah; Mohammed Abullateef Al-Neami

Engineering and Technology Journal, 2008, Volume 26, Issue 10, Pages 1185-1200

The consistency of cohesive soil depends to a large extent on the structure of soil particles
which may be arranged in two systems; dispersed or flocculated. The presence of salts or
acids between the soil particles will alter the arrangement of particles through affecting the
attractive and repulsive forces.
In this paper, a program of laboratory tests is carried out at the University of
Technology/ Baghdad on cohesive soils of different values of Atterberg limits. Samples of
these soils were tested for grain size distribution (sieve analysis and hydrometer). The
falling head permeability test was carried out to determine the coefficient of permeability of
the soils to HCl acid.
The soil parameters determined in the laboratory will be used in the numerical
analysis.The aim of this study is to apply the finite element method to study the steady flow
of pollutants (acids) in a confined aquifer. The program (MULAT) is used for this purpose.
The path of flow of the acid through the soil is traced.
The basic problem solved in this paper is a one of linear flow in a single confined
aquifer. It represents the case of leakage of acids from storage tank and flow of the acids
through the foundation soil. It was concluded from the finite element results that the
maximum head caused by the flow of the acid through the soil decreases with the increase of
the coefficient of permeability and the plasticity index of the polluted soil.