Structural Engineering
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Browsing Structural Engineering by Author "Abrham Gebre (PhD)"
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Item Parametric Study on Shear Capacity of Plate Girders with Web Openings(Addis Ababa University, 2023-06) Mekdes Debir; Abrham Gebre (PhD)This thesis studies parametrically the ultimate shear capacity of plate girders with web holes. The variables include the span length, the opening depth, the opening number, the opening location, and the opening form. This study will provide guidelines for which form of openings to use, how deep to cut the web, where to cut the web, and how many openings to use when web openings are required to pass utility lines and for inspection purposes without adversely reducing the plate girder's ultimate capacity. The finite element software, ABAQUS, was employed as a practical design tool. The accuracy of the developed model is evaluated by comparing its predictions with tests that were carried out experimentally on plate girders, which showed a good agreement in terms of deformations and ultimate loads. The results demonstrated that the behavior of plate girders with web openings is significantly influenced by the shape and depth of the opening, particularly when the opening depth exceeds 50% of the web depth and the opening takes on a square shape. SPGs with two holes each situated up to two times the web depth from supports showed no discernible impact on the ultimate capacity. Increasing the number of openings resulted in additional mid span deflections and a considerable reduction in ultimate capacity. The depth of the opening was found to be the most influential parameter in the sensitivity analysis. The ultimate capacity of the weakest SPGs with web openings is greatly increased by providing steel plates around the openings.Item Resistance to Chloride Penetration of Mortar Using Eggshell as a Partial Replacement of Sand(Addis Ababa University, 2024-06) Betelhem Aziz; Abrham Gebre (PhD)Concrete became more in demand as the building sector grew. Which leads to ongoing quarrying and causes the depletion of natural resources due to excessive mining of natural sand. Also the increase in demand and consumption of egg leads to waste production which will impact the environment. Utilizing of waste materials will reduces the need for natural aggregate, energy, and environmental damage. This study explores the possibility of substituting sand partially with eggshell in mortar production, with a focus on its effects on compressive strength, flexural strength, and chloride penetration resistance. Eggshells, a readily available waste material, offer a sustainable alternative to traditional sand, addressing both environmental and resource depletion concerns. Mortar samples with varying percentages of eggshell powder replacing sand (0%, 10%, 20%, 25%, and 30%) were prepared and subjected to standard testing procedures. The experimental results indicate a decrease in both compressive and flexural strengths with the inclusion of eggshell, compared to control samples. Specifically, the compressive strength decreased by up to 16%, 38% 44% and 49% with 10%, 20%, 25%, and 30% replacement respectively the flexural strength saw a reduction of up to 7.8%, 22%, 31% and 43% with 10%, 20%, 25%, and 30% replacement respectively. Despite these reductions in mechanical properties, a replacement up to 5% is acceptable. For flexural strength 25% is acceptable. The resistance to chloride penetration increases as the percentage of eggshell increases with 0% and 10% replacement showing similar results and 30% showed the highest increase in chloride penetration. And also, there is a decrease in the density of mortar samples with eggshell than the controlled samples because of the light weight of eggshell which can be used for redaction of the overall weight of the structure.Item Shear Strength Analysis of RC Exterior Wide-Beam-Column Joint(Addis Ababa University, 2024-02) Betelhem Desalegn; Abrham Gebre (PhD)In seismically active areas where lightweight constructions are recommended, buildings with long-span floors and heavy self-weight create huge platforms. Ribbed slabs are commonly used to address this issue. Unlike conventional beams, wide beams in ribbed slab supporting frames often exceed framing column widths. Most design codes generally allow following a similar approach to the conventional beam-column joint with some additional beam width limitation which varies among those codes. Research suggests that relying solely on these limitations cannot guarantee adequate joint performance, as the seismic behavior of the joint is significantly influenced by the torsional behavior of transverse beams. This research analytically investigates the structural performance of RC wide beam-column joints with shallow transverse beams under cyclic loading. The accuracy of the FE model in predicting shear capacity performance was validated through comparison with experimental data. A parametric study using finite element analysis was conducted on 48 specimens with different LHS representative combination samples. The study primarily analyzed shear strength of the joints. Using regression analysis for specified range of values, a suggested formula considering transverse beam factors was proposed to be incorporated into the existing expected shear strength equation provided by ACI. An influential parameters of transverse beam were identified by sensitivity analysis. Concrete strength, longitudinal reinforcement ratio, stirrup yield strength, and spacing significantly affected the joint capacity. The shear capacity of the joint showed low sensitivity to changes in the yield strength of longitudinal bars. Smaller diameter bars in the transverse beam showed relatively reduced concrete damage. The study emphasized the importance of incorporating shallow RC transverse beams in the design process of wide beam-column joints. The study presents a systematic approach to improve and quantify shear capacity by considering various combinations of transverse beam parameters. The increased design options for improving shear capacity broaden the scope for practical decision-making, taking into account the availability of parameters and the ease of implementation.Item Solid Waste Bottom Ash as A Partial Replacement of Cement in Concrete Production(Addis Ababa University, 2023-06) Samrawit Yeshaw; Abrham Gebre (PhD)Cement production is hazardous to the environment due to generation of high carbon dioxide (CO2) and heat. To reduce CO2 emissions and protect the environment, researchers have found a wide variety of waste products that can be used as additional cementitious materials for concrete. The most common supplementary cementitious materials are fly ash, blast furnace, silica fume, bottom ash and others. Solid waste bottom ash is one of the supplementary cementitious materials. Solid waste resources are increasingly being used in the production of concrete. Particularly, using recycled solid waste in place of cement, a key component of concrete, has appealed due to its ability to reduce greenhouse gas emissions. The purpose of this study is to investigate the use of Municipal Solid Waste Incinerator Bottom Ash (MSWI) as partial replacement of cement and study the properties of concrete. Concretes were casted to compare the compressive strength, splitting tensile strength, flexural strength. Moreover water permeability test is done on normal strength concrete when cement is partially replaced with municipal solid waste bottom ash at different percentages. The workability of concrete decreased with an increase of percentage replacement of cement by Bottom ash. The obtained results of compressive, tensile and flexural strength show decrement with an increase of BA. However, the replaced concrete samples possess a better water tightness performance than the controlled sample. Solid waste bottom ash can be used to partially replace cement in a normal strength concrete.