Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : finite elements


Behavior of Khassa Chai Earth Dam under Earthquake Excitation

Mohammed Y. Fattah; Haider H. Alwash; Sarah. A. Hadi

Engineering and Technology Journal, 2016, Volume 34, Issue 15, Pages 2784-2795

An earth dam is built of suitable available soils obtained from borrow areas or required excavation which are then distributed and compacted in layers using mechanical means. Earth dams can be constructed of one material to be homogeneous or multiple materials to be zoned dams. Zoned dams are usually advised since zoning allows the use of several different types of material in the embankment which may be available from areas of borrow or required excavations.
This paper presents a dynamic analysis on a zoned earth dam subjected to earthquake motion in which pore water pressure, effective stresses and displacements are calculated. The finite element method is used and the computer program Geo-Studio is adopted in the analysis through its sub-programs SEEP/W and QUAKE/W. As a case study Khassa Chai dam is selected, it is located on Khassa Chai river and constructed of zoned embankment, it has a total length of 3.34 km. The selected earthquake for the analysis is El-Centro earthquake with a period of (10 sec) and different amplitudes of acceleration. The time of the analysis is taken as (600 sec.) with a time step (∆t = 0.05 sec.) to investigate the behavior of the soil for a period of time after the earthquake has stopped, a free vibration period is included in the analysis. It was concluded that, the value of pore water pressure generated at the base of the core is greater than that in the upper parts of dam, the horizontal and vertical effective stress continue to decrease during the period of analysis (600 sec) which indicates that the soil continues to weaken during this period, the horizontal displacement increases with depth of the point from the crest and the largest horizontal displacement will be at the base of the dam at time 60 sec and There is attenuation of the acceleration to some degree depending on the amplitude of the input horizontal acceleration.

Finite Element Simulation of Machine Foundation Resting on Soil

Ekram K. Husain; Qais A. Majeed; Mohammed J. Hamood

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 1272-1283

The paper deals with behavior of machine foundation on elastic foundation. The finite elements approach through ANSYS (version 11) computer software is used for simulation of the dynamic response of the foundation under harmonic loading. As a case study previous analytical analysis problem for machine foundation was reanalyzed. In this problem, the element (solid65) was used for modeling the reinforced concrete foundation whereas the element (solid45) was used for modeling the soil beneath the foundation. The interface is modeled by using three-dimensional surface-to-surface (Target170 and Contact174) contact elements connected with concrete and soil.
It can be noted that the finite element analysis agrees with the analytical results, and the difference in the ultimate displacement is about (7.14, 4.6, 27.6, and 12.5)% when the dynamic force is subjected (along X direction (in-phase), along X direction (out of phase), along Y direction (in phase) and along Y direction (out of phase)) respectively.

Numerical Analysis of Machine Foundation Resting Saturated Sandy Soil

Mohammed Y. Fattah; Nahla M. Salim; Wourood T. Al-Shammary

Engineering and Technology Journal, 2014, Volume 32, Issue 10, Pages 2429-2453

The behavior of machine foundation on saturated porous medium can be considered as a complicated geotechnical problem due to nature of dynamic loads and plasticity of soil which make the analysis and design of foundation subjected to dynamic loads more complex. The main criteria for safe performance of machine foundations subjected to dynamic loads are to control excessive displacements. In this paper, a dynamic analysis of strip machine foundation with multiple thicknesses is placed at the middle of the top surface of saturated sand with different states (i.e. loose, medium and dense), and vertical harmonic excitation is carried out and building up of the excess pore water pressure. The dynamic analysis is performed numerically by using finite element software, PLAXIS 2D. The soil is assumed as elastic perfectly plastic material obeys Mohr-Coulomb yield criterion. A parametric study is carried out to evaluate the dependency of machine foundation on various parameters including the amplitude and the frequency of the dynamic load. The dynamic response (displacement and excess pore water pressure) generally increases with increasing of loading amplitude, but the displacement and excess pore water pressure versus frequency are not smooth and exhibit undulations (peaks and troughs).

Simulation of Deep Excavation in Sand by Finite Element Using Hardening Soil Model (HSM)

Zuhair Abd Hacheem

Engineering and Technology Journal, 2011, Volume 29, Issue 15, Pages 3079-3096

Deep excavation is very important problem in geotechnical engineering and use in construction of tunnel and underground structure. This paper study the deep excavation using Plaxis V8.2 engineering program and simulation the soil behavior by Hardening soil model (HSM) that very sensitive to descript the stress path of deep excavation and the model distinguishes between loading and unloading stiffness compares to The Mohr-Coulomb Model (MCM). The parametric study adopt the variation of sand density (loose, medium, and dense), and excavation width (B = 10,
20, 40, 60, and 80 m). The result conclusions this parameter it's very important on horizontal wall deflection, bending moment of wall, interface stress between soil and wall, heave, and settlement of near ground surface, to make the deep excavation and don’t failure
and reduce of on horizontal wall deflection, bending moment of wall, heave and settlements of near surface and contort on the near building to attainment the safe design and easy construction with optimum dimensions

Dynamic Analysis of Foundations on Saturated Clay Using an Energy Absorbing Layer

Saad F. A. Al-Wakel; Mohammed Y. Fattah; Hussein H. Karim

Engineering and Technology Journal, 2011, Volume 29, Issue 11, Pages 2189-2201

In this study, a method to model the semi-infinite extension (unbounded
domain) of the saturated soil is developed. In this method, the unbounded domain is
replaced by an absorbing layer of finite thickness with properties that appreciably
reduce the wave reflection into bounded domain. In this layer, the soil is represented
by the same properties as in the soil close to the foundation (bounded domain) and a
model of frequency-dependent damping is implemented.
A three-dimensional dynamic analysis of rectangular footing on a saturated
soil is carried out. The foundation is subjected to four cycles of harmonic
force. The coupled dynamic equations with u-p formulation based on the
dynamic consolidation theory are used to simulate the soil skeleton and pore
fluid responses. The solid particles of the soil are represented by linear
elastic behavior. It was found that a decay in wave can be noticed when the
unbounded domain of the saturated soil is represented by the energy
absorbing layer. In addition, the maximum displacement of the foundation
will be decreased due to using the energy absorbing layer in comparison with
the elementary boundaries. The excess pore water pressure that developed
during the dynamic loading will be dissipated with time in a fast rate due to
using the energy absorbing layer.

Investigation of the Behavior for Reinforced Concrete Beam Using Non-Linear Three-Dimensional Finite Elements Model

Israa Kh. AL-Shimmari; Nagham T.Hamad; Waleed A Waryosh

Engineering and Technology Journal, 2011, Volume 29, Issue 10, Pages 1870-1885

This study presents theoretical investigation that reinforced concrete and composite construction might be suitably combined to give a new structural material: composite reinforced concrete. To study theoretically the composite beam, nonlinear three-dimensional finite elements have been used to analyze the tested beam.
The 8-node brick elements in (ANSYS) are used to represent the concrete, the steel bars are modeled as discrete axial members connected with concrete elements at shared nodes assuming perfect bond between the concrete and the steel. The results obtained by finite element solution showed good agreement with experimental results.

Analysis of the Performance of Flexible Pavement under the Effect of Wheel and Thermal Loads

Mohammed Y. Fattah; a Abd. El-Ghany; Shayma; Ahmed S. Abdaljabbar

Engineering and Technology Journal, 2010, Volume 28, Issue 18, Pages 5782-5802

One of the major sources of distress in roads is the cracks that appear in flexible asphalt pavements. Combined wheel and thermal load induced cracking in the form of bottom-up and top-down fatigue cracking.
In this paper, combined effect of wheel loads and temperature is considered in finite element analysis of flexible pavement layers. The heat flow equations are derived and the program (ANSYS V 5.4) is utilized to carry out the analysis. The subgrade layer is modeled as an elasto-plastic material following Drucke–rPrager model for yielding of the isotropic material, while both the asphalt and base layers are
considered elastic. Three different thicknesses for the asphalt layer are tried; namely, 0.05 m, 0.10 m and 0.15 m, respectively. A temperature rise of 40 oC was considered in addition to wheel pressures.
It was found that an increase of wheel pressure from (500) to (700) kN/m2 leads to increase in vertical displacement of about (4 – 8)%. This increase becomes (10 – 22%) when the wheel pressure becomes 1000 kN/m2. The temperature rise leads to decrease in the effect of wheel pressure because temperature leads to expansion (upward movement) reverse to wheel load effect. The effect of wheel load is transmitted directly to the underlying subgrade within the wheel zone. The deformed zone under the wheel becomes larger when the load increases. The maximum displacement increases by about (24%) when the load is
duplicated.