ABSTRACT. The general concept of the finite element method is that the solution gained by it is converging towards to the correct solution with increasing the mesh density. This concept mostly is correct, but sometimes not is the case. Due to the assumptions accompanying the formulation of the method sometimes solution problems are arising especially in the application to shell element, in which the problems of shear locking and membrane locking are arising. These problems often lead to the solution divergence. Although many solutions to these problems have been proposed and have been included in a large number of publications and have contributed to the solve the problems in multiple applications, these problems still prevail in some different shell elements. This problem was clearly demonstrated in this paper by adopting a four-node degenerated shell element and using a reduce integration point in way to solve the shear lock problem. This element was subjected to the batch test and succeeded in all tests except the pure bending test. The application was applied to numerical examples using different mesh sizes and different plots have been done to show the convergence rate of the solution by plotting the maximum displacement versus the mesh sizes. These plots are explained clearly the problem of solution divergence after a certain point. The paper focused on the study of the point at which this divergence occurs by drawing multiple diagrams of the examples taken, by taking several ratios of thickness to the length of each element after meshing (t/Ln). These examples include curved shell and flat plate. By observation, the coincidence ratios at which divergence occurred have been found to be equal to 0.23 for the curved shell and equal to 0.9 for the flat plate shell problems. To examine these ratios different examples of known exact results have been taken. The accompanying mesh size with the ratio was calculated for each example. The results obtained were found be acceptable when compared with the exact one which gives a ratio between 0.999 and 1.130 out of the exact result.

ABSTRACT. The paper presents a numerical study of the chloride induced corrosion process in lap splice joints in concrete beams. The problem is simulated using a recently developed 3D Chemo-Hygro-Thermo-Mechanical Finite Element model for concrete. The model is used to understand corrosion induced crack propagation at different corrosion levels, corrosion current intensity, produced mass of rust, corrosion expansion and induced stress in concrete at the lap splice joint. The corrosion induced cracking of concrete cover is compared with the experimental results from the literature. It is shown that the model is able to realistically replicate corrosion induced damage of lap splices in concrete.

ABSTRACT. The introduction of openings into reinforced concrete (RC) elements leads to reductions in the element’s overall structural capacity and stiffness. These reductions attributed to stresses concentrations and local cracking at the openings region. This paper presents a study aimed at investigating the influence of web openings at shear span of RC beam on its shear behavior. A total of three beams with circular openings and one beam without opening were fabricated and tested. The opening location and size, and shear span-to-depth ratios, were considered as the main parameters. The FE model using ANSYS14.5 software was calibrated with the experimental results to ensure that the simulation process is correct. Furthermore, the specimens were analyzed using ANSYS14.5 with considering the above mentioned parameters. The results showed that the early collapse of the beam occurred when the openings located in a high shear region. Furthermore, by comparing the non-linear FE analysis results with those from experimental tests, results were in accordance. Finally, an analytical equation for predicting the shear strength of RC beams with circular openings was proposed, and compared with those from FE model.

ABSTRACT. Flat Slab, also known as beamless slab, is one in which reinforced concrete slab directly rests on columns. The reinforced concrete Flat slab system is very popular in multi-story construction throughout the world since it has shorter construction time, simple formwork, flexibility in the plan layout and use of space. However, reinforced concrete flat slab buildings have often experienced problems in lateral loading events, particularly seismic events, due to the absence of beams. The efficiency of flat-slab reinforced concrete structures in resisting gravity or lateral loads relies mainly on the behaviour of slab-column connections to restrict the lateral motion and inter-story drift. However, there is no enough research work related to the strengthening of slab-column connection. Hence, there is a need to investigate such an issue experimentally and theoretically. This research aims to investigate the potential use of carbon fibre reinforced polymer (CFRP) to strengthen six different types of flat slab-column connections and to compare their performance with their response before being strengthened. In this study, six different types of reinforced concrete slab-column connection models were tested under gravity and lateral loads using Abaqus FE analysis software package (2016). This is to provide a numerical model that can be used to investigate the effects of using CFRP to strengthen the slab-column connection. In addition, a parametric study was conducted to investigate the effects of different parameters on the overall behaviour of the slab-column connections. Three parameters were examined in this study: mesh sensitivity, the bent length of the CFRP on the column side, and CFRP thickness. The results of the parametric study showed that, by increasing the thickness of the CFRP, it was possible to increase the moment carrying capacity and the load carrying capacity up to 25%. The research concludes that using CFRP to strengthen the reinforced concrete slab-column connections has some advantages and disadvantages. Generally, the results indicate that the strength and stiffness of a connection can be significantly increased, but with a noticeable decrease in the ductility.

ABSTRACT. In this study, a repairing of preloaded RC beams with openings strengthened with steel plate was studied by using finite element package ANSYS14.5. To ensure that the elements, convergence criteria, and material properties are adequate to model the behavior of the RC beam and to ensure that the simulation process is correct, the FE ANSYS was calibrated with published experimental data. The effect of pre-damage level and loading mechanism were considered as main parameters. Furthermore, birth and death technique was used to model the cracks before strengthening stage. In this technique, loading was first applied till the objective cracking, followed by steel plate application, and then the load was continued to failure. The result showed that pre- damage levels and the steel plate strengthening have a great effect on the failure mode and ultimate load of RC beam. In addition, the results showed good agreement with those obtained from published experimental tests. Based on FE using ANSYS an ACI guidelines, an analytical equation for predicting the shear capacity of RC beams with openings strengthened by steel plate under sustained load was then proposed. A comparison of these results yielded valuable conclusions.

ABSTRACT. In different engineering applications, the recent advent of new composites is promoting the replacement of traditionally employed materials. In construction industry, Fiber Reinforced Polymer (FRP) composites are gaining a significant attractiveness because of their versatility, enhanced durability and resistance to fatigue and corrosion, high strength-to-weight ratio, accelerated construction, and lower maintenance and lifecycle costs [1]. However, when it comes to modeling and simulation these materials still pose a challenge. Because they exhibit rate-, temperature-, and pressure-dependent as well as anisotropic material behavior and undergo large deformations during loading processes. In this contribution, an invariant-based anisotropic plasticity model is formulated and implemented within the co-rotational framework for it’s used in geometrically nonlinear analyses of FRP composites. Herein, the invariant representation character of the adopted modeling framework allows the incorporation of the anisotropic response of these materials to be performed. In practical terms, the anisotropic constitutive equations are represented in the format of isotropic tensors functions. From the modeling point of view, the nonlinear inelastic behavior of these materials is considered through the definition of anisotropic yield surfaces and non-associative plastic potential functions, see [2]. Non-associated plastic potential functions are introduced in order to model more realistic plastic deformations in FRP composites. The model is then cast in a co-rotational framework so that finite deformation responses can be simulated, wherein displacements and rotations are assumed finite while strains are assumed to be within the small to moderate rate [1]. On the computational side, specific aspects with regard to the corresponding algorithmic treatment and numerical implementation of the proposed models are tackled. Particularly, novel closed-form expressions necessary for the consistent finite element local and global implementations are derived. The performance of the proposed model is assessed via a set of numerical simulations using the commercial finite element software ABAQUS, which demonstrate its applicability and robustness.

References [1] Zoghi, M. (2013). “The International Handbook of FRP Composites in Civil Engineering”. In: Book, CRC Press. [2] Dean, A. (2017). “Material Modeling of Short Fiber Reinforced Polymeric Composites: Theory, Numerical Aspects, and Applications”. In: Dissertation, Gottfried Wilhelm Leibniz Universität Hannover. [3] Masud, A., and C. L. Tham (200). “Three-Dimensional Corotational Framework for Elasto–Plastic Analysis of Multilayered Composite Shells”. In: The American Institute of Aeronautics and Astronautics 38, pp. 2320– 2327.

ABSTRACT. This study investigates the response of fibre-reinforced masonry bricks under loading. Samples are prepared with various fibre content. Extensive compression, tensile and flexural tests are carried out on brick samples, with the purpose of understanding the effect of fibre content on properties of masonry bricks. Based on the experimental results, two constitutive models are proposed. These models are stress-strain curves for fibre-reinforced masonry bricks to be used in the current design procedures plus empiric correlation between the brick strength and fibre content. The validation of the models is given using finite element software, ABAQUS. The findings presented in this paper suggest that natural fibre such as sugarcane bagasse and chicken feathers fibres are a feasible fibre option for brick production. In addition, optimising the geometry of the newly developed bricks using finite element software, Solid Works is identified as follow up research.

ABSTRACT. Abstract This study aims to assess the approach to plan the water supply system for the Khartoum New International Airport (KINA), which is located south of Omdurman, 40 km south-west of the city centre of Khartoum. The authors by developing and judiciously applying a Decision Support System (DSS trees and matrices) succeeded in obtaining an optimum water supply system design for such a large infrastructure project. It should be noted that, DSS integrate a broader range of topics, addressing the problem from a macro perspective. The purpose of a DSS is to create tools that help maximize the efficiency of a decision-making process through the application of relevant knowledge The Khartoum New International Airport (KINA) study area is 103km2 and has three identified water resources namely Jebel Aulia dam, ground water and El Mansorab khor water harvesting project. For El Mansorab khor, GIS was used for both delineation and physical characteristics. The outflow was carried out by using HEC-HMS software. The wells tests were taken from the Master Plan Study of KINA. The Jebel Aulia treatment plant in the downstream was taken as main water supply. All sources were conceded to the tank which is to be located in the highest point of KINA. It should be noted that, The seven strategy evaluation criteria for KINA considered are: Proximity to the Khartoum New International Airport (KNIA), Quantity of water, Affordability, Dependability, Environmental quality, Quality of the water and Permitting feasibility.

The study concluded that, the most convenient, economic and reliable source for water supply is Jebel Aulia treatment plant. Therefore, it had been suggested that the water supply for KNIA is going to be composed of a water transmission line that delivers water from Jebel Aulia water treatment plant. Moreover, the khor had seasonal flow just three month per year, and also wells water quality was not complying with the drinking water standard.

ABSTRACT. Bara Basin is one of the most important groundwater basins in west-central Sudan in terms of groundwater availability, water quality and degree of utilization. The basin complex is formed of a number of sub-basins which constitutes the northern extension of the White Nile Rift System and the western extension of the Blue Nile Rift System. Water levels are expected to decline drastically by withdrawals of water from Bara aquifer especially in the vicinity of Al-Sidir wellfield located near Bara town. Further developments in the wellfield are planned to cope with fresh water supply needs of El Obeid City, which raise concerns about the sustainability of the aquifer and the feasibility of its production. Optimization analysis was conducted using USGS’s Groundwater Management Process (GWM) to demonstrate approaches that could be used to evaluate possible future pumping scenarios intended to prolong the productivity of the aquifer and to delay excessive drawdowns. The optimization analyses were based on an existing calibrated groundwater-flow model of Bara aquifer. Two optimization objective functions were formulated, each formulation was set up to maximize total withdrawal rate, subject to withdrawal-rate and hydraulic-head constraints at the location of each well. A user interface was developed for GWM using Visual Basic for Applications programming language (VBA) on MS Excel to ease the utilization of the software. The analysis has shown that pumping of the existing 40 wells in Al-Sidir wellfield at the design capacity (1500 m3/day) will result in a drawdown of 100m in 50-years period. Optimized operation of the wellfield can reduce drawdowns to 50 meters with 31 operating wells at varying pumping rates (Scenario 1), or a 60 meters reduction with 33 operating wells at varying pumping rates (Scenario 2).

ABSTRACT. The increasing number of people in some cities and regions has made the issue of human health and cleaning the environment more problematic. Many chemical and other pollutants are augmented in the atmosphere, water and food. Theses may cause ill-health and deteriorate cleanliness of the human environment. It is to be noted that neither advances in science nor development in technologies can create the right alternative to the value of pure and open nature to man.

The aim of this research is to provide energy and reduce proportion of air pollution with greenhouse gases, as well as contribute significantly to noise reduction through the use of non-traditional solutions such as plantig of roofs of buildings.

In the present study beds were manufactured to resemble three types of surfaces. The first bed simulates dense green surfaces planted with flowers. The second bed replicates large green surfaces planted with green grass with a thickness growth layer of 7, 14 and 21 cm, for each. These surfaces were compared to the third one, which represents traditional surface tiles.

Experimental results showed that the efficiency of noise reduction increases with an increase in thickness of medium of growth. Noise reduction ratios for the dense green surface and the wide green surface attained 29.49, 33.9, 40.39%, and 33.24, 41.50, 48.24%, respectively, as compared to a conventional surface and following medium of growth.

The results showed that the green surfaces had a great ability to modify the temperature inside houses. Nevertheless, the effect of large green surfaces was better than dense green surfaces. The percentage of thermal change of the wide green surface recorded 16.56 to 29.63% and the dense green surface indicated values of 12.27 to 20.99m as compared to the traditional surface and according to the medium of growth. This is where the efficiency of temperature adjustment increases with the thickness of the growth medium.

The ratio of increase of oxygen for the wide green surface was 54%, while the oxygen content over the condensed green surface was 36% when compared to the conventional surface.

As such, it is recommended to use wide, dense green surfaces to save energy, reduce noise pollution, increase oxygen in the surrounding environment, and reduce pollution from vehicle exhaust, laboratories and other sources.

ABSTRACT. Produced water associated with crude oil production is considered as waste water. In most of the Sudanese oilfields processing facilities, evaporation ponds are used to receive the produced water. The objective of this work is to study the probable effects of seepage from existing evaporation ponds that were constructed many years ago to store produced water from field production facilities (FPFs) in number of Sudanese oilfields. Seepage assessment methodology involved of electrical resistivity measurements, drilling boreholes and collecting soil samples at different depths, geotechnical laboratory tests, water and soil tests and finally incorporate all testing results and geophysical interpretations for each location into a computational model to predict seepage front in vertical and horizontal directions. Electrical resistivity method basically the vertical electrical sounding (VES) has been employed during this study. The geophysical work was carried out with sensitive Mini-Sting Resistivity meter manufactured by Advanced Geosciences Incorporation. More than 60 VES measurements were conducted using Schlumberger array. Geotechnical investigation program was carried out included field work and laboratory testing. The investigation started with the field work by drilling 10 boreholes, collecting representative disturbed and undisturbed soil samples. Soil profiles and the engineering properties of the subsoil were tested and interpreted. Water and soil samples were tested in two laboratories for environmental properties, pH, TDS, oil content and heavy minerals. Historical data about water quality from the evaporation ponds as well as from nearby water wells were collected and compared with the lab results. It was found that, the majority of these tests showed normal concentration of different chemicals in evaporation ponds, soil till depth of 15 meters and other oil wells till depth of 400 m. Thorough comparison of these test results indicates no seepage evidence in these waters and/or soils. Comparison is made by investigating old data with new data from several laboratories for TDS, pH and other constituents to see if there is considerable change with time. When comparing the test results to the national and international limits for pollution discharge, the obtained results are far below standard limits. Computational seepage model was created to predict seepage advancement in each location. It has been found that both the current seepage level and the predicted one will not reach the ground water static level in all five locations. Risk assessment was performed for five different scenarios. Generally, and according to the laboratory test results for the five locations, the likelihood for vertical or lateral seepage to contaminate ground/surface water and soil is rare, i.e. extremely unlikely or impossible.

ABSTRACT. Since the past decades, the increasing of anthropogenic activities, especially in oil and gas industrial areas have affected the environment (air, water and soil). This is a global issues which happening throughout the world. Sudan also faces these problems as it has been producing and exporting oil since August 1999. Produced water is considered as a by-product of oil and gas production and most commonly treated as a waste for disposal rather than reuse and is the largest volume waste stream associated with oil and gas exploration and production. Recently produced water quantities in Sudan oilfields (Western Kordofan State) increased rapidly due to the increase of the water cut percentage of the produced wells for all productive oilfields. Bioremediation projects were constructed to treat the produced water coming from Central Processing Facilities (CPF) at Heglig, and other Field Production Facilities (FPF). The discharge of the treated produced water used ONLY for irrigation of forests area. Globally as weather changes its pattern and climate in the worldwide, the demand of freshwater supply has increased. This problem is particularly occurring in Western states of Sudan includes Western Kordofan State where water resources are particularly stressed given unprecedented drought and competing demands for ever scarcer water. This research paper will propose an integrated management of the produced water and its disposal is further evaluated for potential options of reuse; it may contribute to minimize the problem of drought on this part of Sudan.