This paper includes an analysis to asses the behavior of stone columns using the finite element method and to provide bases and information helping geotechnical engineers to design foundations resting on weak soils reinforced with stone column. The axisymmetric quadrilateral element is adopted in the finite element program to simulate the soft soil and the stone column while the one-dimensional element is used to simulate the soft soil and the stone column-soil interface. The nonlinear inelastic stress-dependent model is used to simulate the behavior of the soil and the interface throughout the incremental loading stages adopting nonlinear parameters obtained from triaxial and direct shear stress. The analysis is carried first on a selected basic problem, to clarify the nonlinear of the column, in which a selected geometry, boundary condition, and material properties for both soil and interface as chosen. The rest of the analysis is grouped into the effect of some of the parameters concerning the geometry of the stone column and the material of column and adjacent soil are investigated. It was found that the increase in stone column length and in relative stiffness of stone column material to soil play an important role in increasing ultimate capacity of the stone column and in reducing settlements.
A series of experimental tests were carried out to investigate the behavior of high strength concrete filled double skin steel tubular (HSCFDST) columns. Fourteen column specimens were tested in the present study, taking into account the effects of the shape of column cross section (circular or square), the hollowness ratio, and the slenderness ratio. For comparison, two of the tested specimens were filled with normal strength concrete. It was seen that the ultimate axial strength of the square HSCFDST columns is greater than that for circular ones, in spite of that the sectional properties were approximately equal. Also, it was found that for both circular and square column specimens, the ultimate axial strength of HSCFDST columns was inversely proportional to their hollowness and slenderness ratios. CFDST column specimens filled with high strength concrete compared with those filled with normal strength concrete increased stiffness and ultimate axial strength, but give unexpected results for the ultimate axial strength, therefore the suitable choice for the section properties of the inner steel tube is required. The experimental results and analytical approach that developed by other researchers shown good agreement.
Abstract In this study, a theoretical analysis is presented to estimate the in-plane large displacement elastic stability behavior of structures having non-prismatic members of linearly and nonlinearly varying sections resting on elastic foundation (Winkler type) and subjected to static loads applied at joints only. The analysis adopts the beam-column approach and models the structural members as beam-column elements resting on distributed springs. The formulation of beam-column element is based on Euler approach allowing for the influence of the axial force on bending stiffness. Changes in member chord length due to axial deformation and flexural bowing are taken into account. The stability and bowing functions are estimated using methods of finite differences and finite segments. Also, approximate results have been obtained by using approximate stability and bowing functions of linearly and nonlinearly tapered members resting on elastic foundation. A computer program has been coded in QB language to carry out the proposed analysis of structures with prismatic or non-prismatic members of linearly and nonlinearly varying sections resting on elastic foundation. As a result of this study; the only difference between the analysis of non-prismatic members resting on elastic foundation and those which are not, when adopting the beam-column approach, is represented in the stability and bowing functions, and this is reflected directly on the tangent stiffness matrix.
Composite columns are frequently used in constructing high-rise structures because they can minimize the size of the building's columns while increasing the floor plan's usable space. This study aims to create a nonlinear 3D finite element model for square composite columns designed for solid and hollow columns with various multi-skin tubes subjected to loads at eccentricities of (30 and 60) mm, compressive strength, and mesh size using the ABAQUS software. The comparison was based on the experimental data of six references of composite columns. While the compressive strength of concrete increases, the stiffness of the composite column rise. The ratio of concrete compressive strength values for composite column increased by (0, 12.3, 17.8, and 26.7 percent) for (fc'=25, 31.96, 35, and 40) MPa, respectively. The results of the different mesh sizes (20, 40, and 60) mm are showing; The experimental results and the finite element solution developed using the (20 X20) mm element correspond well. The nonlinear finite element analysis method was used, and the finite element outputs results were confirmed to be in favorable agreement with the experimental data
Brick as a construction material can be considered one of the most common materials used for a very long time to construct buildings in iraq. The historic building represents one of the most important figures representing the rich history of iraq, which is built with bricks. Due to the aging of this type of building, a necessary improvement and retrofit need to occur. The paper investigates the ability to use different kinds of materials such as cfrp and srg to enhance the brick columns' structural capacity. From the results and discussions, it can be concluded that these materials are suitable to be used for this purpose with some limitations due to brick capacity itself.
Abstracte: The stress-strain behavior of any type of soil depends on a number of different factors including density, water content, structure, drainage conditions, strain conditions (i.e., plane strain, triaxial), duration of loading, stress history, confining pressure, and shear stress. In many cases it may be possible to take account of these factors by selecting soil specimens and testing conditions which simulate the corresponding field condition. Even when this can be done accurately, however, it is commonly found that the soil behavior over a wide range of stresses is nonlinear, in elastic, and dependent upon the magnitude of the confining pressure employed in the tests. In order to perform stress analysis of soils, it is desirable to employ techniques, which account for these important aspects of soil behavior.
This study introduce a review on structural behavior of different structural elements such as beams, slabs, column….etc, under different type of loading. Through this review one can see the effectiveness of using ferrocement in casing slabs, beams subjecting to bending or impact load. Also the ferrocement make an essential role in strengthening of damage columns and beams.
The concern over increasing needs for drinking water and awareness for development of systems to improve water quality both for drinking purposes and for effluents from wastewater treatment and industrial facilities have provided incentives to develop new technologies and improve performance of the existing one. Adsorption technology has many advantages over other treatment methods such as simple design, low investment cost, limited waste production, etc. Synthetic water with a dosing of artificial copper solution (Cu No3) was passed through a PVC column (15 cm diameter, 100 cm length) containing limestone as a filter media in three different sizes, using three different hydraulic rates, and three initial influent copper concentrations (7.04, 4.39, 1.72) ppm .For this study, three experiments have been conducted; continuous batch and field experiment. The up flow roughing filtration is the suitable technique to recover heavy metals present in aqueous solutions, without the need of adding further substances. The filtration results demonstrated that the smaller size of filter media (3.75) mm gave higher removal efficiency (93.75 – 98.80) % than larger filter media (9.50) mm which gave removal efficiency of (67.61 – 94.0) %. This is due to the large specific surface. The smaller size of limestone achieved the longer detention time (49) min, so the removal of Cu was more than (90) % for the (50) min of experiment. At lower flow rate (0.16) L/min, the removal efficiency was higher than at higher flow rate (0.77) L/min. At high flows, there is a reduced period of surface contact between the particles and copper solution. This study also involved three different batch experiments .The removal efficiency was (93- 97) % for the three types of limestone which indicates the importance of limestone media in the removal process. This also indicates that the removal efficiency was increasing with the increase of the limestone volume. Field experiment has been conducted using wastewater from Al- Dura Electric Station on the three types of limestone so that to ensure the laboratory tests. It was achieved good removal efficiency range from (87.5) % to(97.5) % at the high adsorbent dose .To calibrate the physical model, a computer program of multiple regressions is used to assess the relative importance of the predicted variables. The partial correlations indicate that influent concentration of copper, surface loading (flow rate), and detention time are the most important variables while the size of limestone is not important as others.
This study was determined specified characteristics of Iraqi silica sand , touse it in the drinking water treatment rapid gravity filters. These properties includes grain size ,uniformity coefficient , grain shape , porosity , density , durability, chemical content and capability of solubility in the acid ..this study explained that the Iraqi silica sand has high degree at mechanical and chemical stabilities .The e filter column was operate for many cycles , the average results of raw water and treatedwater for variable values (turbidity , total suspended solids and total bacterial count) was taken . The study showed that possibility of use the Iraqi silica sand in the westernIraqi desert in the rapid gravity drinking water treatment plant filters . when the raw water has initial turbidity (5.24 NTU) ,the study and the experimental tests showedthat the average removal efficiency of turbidity , T.S.S ,and T.B.C of (82.9%,82.8%and 79.5%) respectively . when the raw water has initial turbidity (9.58 NTU) ,the study and the experimental tests showed that the average removal efficiency of turbidity , T.S.S ,and T.B.C of (79.4%,78.7% and 74.1%) respectively . when the rawwater has initial turbidity (28.35 NTU) ,the study and the experimental tests showedthat the average removal efficiency of turbidity , T.S.S ,and T.B.C of (72.6%,72.7%and 60.9%) respectively