Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Earthquake

Settlement of Shallow Foundation in Dry Sand Under an Earthquake

Mohammed A. Al-Neami; Falah H. Rahil; Ahmed F. Hussain

Engineering and Technology Journal, 2021, Volume 39, Issue 8, Pages 1206-1215
DOI: 10.30684/etj.v39i8.527

Seismically induced settlement of buildings with shallow foundations resting on dry sand soils has resulted in severe damage in recent earthquakes. A multi-degree of freedom shaking table and a fixed container were manufactured and used to study the foundation settlement. Series of shaking experiments on the shallow foundation situated in a center of the container and atop of a dry sandy soil has been performed to identify the mechanisms involved to calculate the foundation settlement induced by earthquake shaking. In this research, the important factors are identified, including shaking intensity, the soil relative density, the degree of freedom and the building’s weight. Two relative densities (55 % and 80%) are used and three local magnitudes of earthquakes (5.8, 6.4, and 7.2) (Anza, Jalisco, and Guerrero) respectively with one and two degrees of freedom. The results of the shaking indicated that shallow foundation settlement on the dry sand increases with the increase of the local magnitude of earthquakes and maximum acceleration. In the case of Anza, the percentage decrease in the settlement between the relative density of 55% and 80% for systems (x and xy) is (47% and 42%) respectively. While in the case of Jalisco and Guerrero, the percentage decreases in their settlement and for the same systems is (11% and 57%), (36% and 36%) respectively. The degree of freedom has an impact on the foundation settlement; it is proportional to the degree of freedom. Also, the results show that the settlement decreases when the relative density of sand increases.

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.

Evaluation of the Hydrodynamic Pressure Effect of Cylindrical Liquid Storage Tank on The Granular Soil Behavior Under Seismic Excitation

Ahmed A. Hussein; Mohammed A. Al-Neami; Falah H. Rahil

Engineering and Technology Journal, 2021, Volume 39, Issue 1A, Pages 64-78
DOI: 10.30684/etj.v39i1A.1697

Many liquid storage tanks around the world have been affected by earthquakes, and the seismic analysis of such tanks is much more complicated due to the Fluid-Structure Interaction. Besides, when the soil properties are taken into the consideration, the analysis with the Fluid-Soil-Structure Interaction becomes very complicated. In this paper, a series of shaking table tests are conducted on a model of the cylindrical water tank rested on dry granular soil and the equivalent load is considered to study the effect of hydrodynamic pressure generated in the storage water tank on the soil behavior. An experimental investigation of (1:100) scale model has been carried out on a shake table that was manufactured with specific mechanical parts and flexible laminar shear box. The preparation of the test included three cases in different relative densities (medium, dense, medium-dense). Three earthquake histories (Kobe, El-Centro and Ali Al-Gharbi) were implemented to study a wide range of the acceleration. The results showed that the acceleration at the bottom-depth of the soil column is slightly higher than at the mid-depth, while at the top portion of the soil column, the acceleration comparatively becomes less than that at the mid-depth. The settlement due to hydrodynamic pressure in the storage base tank is significantly reduced compared with results of nonhydrodynamic pressure in all cases of the acceleration history. In addition, the lateral stress at the surface gives higher than the stress at a depth equal to the diameter of the base tank.

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.