Zede Journal

Investigating the effect of sludge/clay ratio and firing temperature on the compression strength and water absorption capacity of brick using response surface methodology

Tsegay Gebremedhin — 2023-08-23

Presently, the sludge generated from the Zero Liquid Discharge (ZLD) facility in Hawassa Industrial Park is collected inside a nearby big constructed shed without any treatment. This study investigated the utilization of this textile sludge as input for the production of brick construction material as the sludge management tool. The study focused on finding optimum parameters for the production of bricks using response surface methodology. The proportion of sludge mix and the firing temperature were selected as the study independent parameters with the compressive strength and water absorption as the experimental responses. Based on the analysis of variance (ANOVA), linear and quadratic model equations were selected for compressive strength and water absorption capacity, respectively. The regression analyses have shown that the model equations ware satisfactory enough to predict the selected responses within the experimental range with 94.98 % and 99.71 % variability in the same order. Based on numerical optimization, a sludge mix of 18.66 % and a temperature of 1000oC were selected as optimum synthesis parameters predicting bricks with 3.5 MPa comprehensive strength and 16 % water absorption.

Probabilistic assessment and field test verification for strength evaluation of bridge with defective girde

Abraham Gebre — 2023-08-23

The use of high-quality materials, regular inspection and testing of constituent materials, appropriate curing processes, and an acceptable overall construction methodology are all required for bridge construction. Failure to handle the aforementioned ways causes the bridge to operate poorly, jeopardizing its load-carrying capacity. As a result, determining the load carrying capacity of the bridge and assessing its safety are critical. This study investigated the performance of a defective girder of a Reinforced Concrete (RC) bridge (located at km 69+937 along the Agulae-Berahie road segment) caused by failure of concrete to achieve the desired compressive strength. Various assessment methods were used to assess the strength of existing defective girder. Following the uncertainty of random variables, a probabilistic assessment approach was used. A field load test was also used to correlate and verify the numerical result. The findings reveal that the bridge under investigation is safe against the design and legal loads specified in ERA Bridge Design Manual.

Assessment of distributed non-linear fiber models

Anur Oumer — 2023-08-23

The study evaluates existing numerical nonlinear modeling techniques used in seismic analysis. Experimentally tested RC bridge column specimens have been taken as a case study and modeled in OpenSees finite element software. The study shows that the distributed forcebased (FB) fiber models provide a more accurate result in capturing the nonlinear behavior of the RC bridge column that exhibits strain-hardening behavior. In contrast, the distributed displacementbased (DB) fiber models overestimate the ultimate capacity of the RC bridge column for sections exhibiting strain-hardening behavior. The study shows that for nonlinear analysis using distributed displacement-based (DB) fiber models, members should be divided into several elements to capture the inelastic response accurately. For the section exhibiting strain-softening behavior, both the distributed force-based (FB) and displacement-based (DB) fiber models are affected by localization issues. To overcome the localization issues, threelevel of regularizations have been compared: 1) Applying regularization only to concrete, 2) Applying regularization only to steel 3) Applying regularization to concrete and steel materials. The level of regularizations was observed to have a significant effect in capturing the softening behavior, such as concrete crushing/spalling or rupture of reinforcing steel bars.

Effect of toxic heavy metals at downstream irrigation of wastewater treatment plant

Johnny Girma — 2023-08-23

For several years, domestic wastewater from Addis Ababa's seven sub-cities has been treated at Kality domestic wastewater treatment plant. Despite being designed to treat domestic waste, certain industrial wastes were discharged into the treatment plant system via point and non-point sources, causing a number of problems. The effluent from the treatment plant was primarily used for irrigation by local farmers in the Akaki-Kality sub-city. To identify and quantify heavy and toxic heavy metals in treatment plant effluent, irrigated soil, and vegetable plants, as well as to determine how they affect human health downstream, α cross- sectional study design was used. Liquid samples were collected at the Up flow Anaerobic Sludge Blanket reactor (UASB) inlet and outlet, trickling filter and secondary clarifier outlets, a soil sample from a cultivated field, and plant samples such as habesha gommen and kosta grown using the effluent. The presence and concentration of heavy and toxic heavy metals were determined in the samples, and the ability of unit processes such as the UASB, trickling filter, and secondary clarifier to remove toxic heavy metals was assessed. The laboratory tests revealed that majority of the toxic heavy metals were present in the samples analyzed (chromium, cadmium, arsenic, copper, lead, and manganese) and the unit processes were inefficient to remove these metals.

Assessment of controlled blasting technology employed at addis ababa riverside green project - friendship square

Wang Yang — 2023-08-23

This research paper presents an overall assessment of the planning and execution of controlled blasting operations that took place as part of the Addis Ababa Riverside Green Development Project. The objective of the paper is to highlight the process of a successfully completed one-of-a-kind operation in Ethiopia. The application of liquid CO2 fracturing blasting technology in the prevention and control of rock burst in the project shows that CO2 fracturing blasting reduces the stress concentration of rock burst system and transfers energy to the deeper part, and there is no open fire in blasting. It is a new, safe, and efficient technology to prevent rock burst, which can be applied widely. Overall, the results of the assessment show that the controlled blasting operation is executed in an efficient manner. It has been discovered that there were only minimal to negligible vibrations recorded on the day of the blasting. Photo analysis techniques also reveal that the rock fragmentation output is of acceptable quality. There was no interference with other operations, gave reproducible results, and minimized entry into sensitive locations. Productivity performance assessment also indicate that 200,000 m3 of hard rock material has been excavated and hauled away in just 21 days which can be labeled as a very efficient performance.

Capacity analysis of selected major intersections on the route autobus Tera-Kality bus stations and mitigation measures

Abel Kebede Bekele — 2023-08-23

Engineering mitigation measures proposed in order to improve the existing levels of service for major intersections. The adjustment to the existing cycle time, delineation of movements on existing lane configuration and geometric modifications to observe the improvements on the respective levels of service were among the proposed mitigation measures. It was hypothetically believed that there exist short comings on the route Autobus Tera - Kality bus stations from congestion and level of service points of view. Subsequently, four signalized intersections were selected based on statistical outputs of mixed type of questionnaire. They were then analyzed by using software tool (SIDRA) so that the outcome could be used as a source of information and data for transport sector organizations and academic reference. Accordingly, the level of service of Eliana hotel site improved from level F to D & the average delay from 167.3 seconds to 54.7 seconds and level of service of Immigration site improved from level F to E & the average delay from 435.5 seconds to 68.7 seconds. Moreover, level of service for both Harambae and Saris Adey Ababa sites improved from F to D & the average delay from 642.6 seconds to 54.2 seconds and from 865.1 seconds and 49.13 seconds, respectively.

Damping properties of concrete with sand coated rubber aggregates

Yisihak Gebre — 2023-08-23

Waste tire rubber disposal causes major environmental problems and serious threats to human health. A viable solution for reducing waste tire rubber is to reuse the material in concrete production. Since ordinary concrete is brittle, and has low energy absorption capacity, elastic rubber could possibly improve the damping behavior of concrete. In this study, the mechanical and dynamic properties of concrete with partial replacement of coarse aggregate by rubber and epoxysand coated rubber at different volume fractions ranging from 5 to 25% were investigated. Test results indicate that uncoated rubber chips in concrete cause a significant reduction in strength. However, epoxy-sand coated rubber aggregate partial replacement improved the interfacial properties of the rubber. Accordingly, an optimum compressive strength was achieved with 15% epoxysand coated rubber aggregate replacement. Furthermore, the maximum increment in damping ratios for uncoated and sand-coated rubber aggregates were found to be 58% and 23%, respectively as compared to normal concrete. Hence, the utilization of epoxy sand coated rubber presents a promising approach to enhance the dynamic performance of concrete structures, without affecting their mechanical properties.

Fault tolerant digital controller for dc-dc switching power converter using modular redundancy

Daniel Dilbie — 2023-08-23

Power converters and regulators are the main and critical building blocks of all electronic systems. In applications prone to transient faults, such as particle strikes, spatial redundancy techniques can improve the reliability significantly. The design of a fully digital DC/DC switching buck converter regulator based on a fault tolerant modular redundancy architecture implemented on SRAM FPGAs is presented. Transient events such as single event functional interrupts (SEFIs) are the dominant effects in SRAM-based FPGAS. SEFIS result in missing pulses in the generated PWM control signal of the converter that cause large transient drops at the converter output. In this work, triple modular redundancy (TMR) technique is used to implement spatial redundancy. This approach is used to triplicate the physical digital blocks on FPGA such that faults on one of the modules can be detected and corrected while the system works uninterrupted and with correct output. Experimental results indicate that with triple modular redundancy, the power converter can withstand up to 5x more doze of faults as compared to conventional power converters.

Modeling and simulation of a micro-hydropower system for rural electrification (a case study of Temecha river, Amhara region, Ethiopia)

Getnet Belie Endalie — 2023-08-23

It is well known that, there is an imbalance of electricity demand and supply in Ethiopia. Development of the Micro hydro power (MHP) system is an important technology to solve the problem. The main objective of this study was to do modelling and simulation of a micro-hydropower system for rural electrification in the case of Temecha River, Ethiopia. Yearly flow data were collected from Ethiopian Basins Development Authority and used to estimate the design flow rate. Next, modelling and simulation were done by using MATLAB SIMULINK. Some of the SIMULINK results were power and flow duration curves, and others. The nethead and design flow rates were found to be16.34m and 0.5731m3/s, respectively. Based on the preliminary analysis, the turbine selected for the site is a Kaplan turbine. It is found that, the power output of this system is greater than the electricity demand of the selected site for 346 days of the year. Thus, the systemic found to be efficient in terms of generated electrical power as compared to similar works reported in the literature. The scale of the design can be re-modified to be implemented in other remote areas having river resources.

Predictive maintenance of ball bearings using convolutional neural networks (CNN)

Arsema Derbie — 2023-08-23

To this day, numerous maintenance actions follow preventive and run-to-failure methods. In this work, it has been attempted to show the power of predictive maintenance (PdM) from vibration data using a machine learning technique implementing convolutional neural networks (CNN). Actual data was collected from six different bearings on a machine element fault analysis test rig. The bearings were of the ball bearing type, where one of them was healthy and the rest were faulty at the inner race, the outer race, the rolling element, or a combination of these three, and another had severe damage at either the rolling element or the rings. From the vibration signatures specific to the health status of the bearings, a powerful deep learning convolutional neural network model was built. The model was able to successfully classify the states of bearings with accuracy values ranging between 76.7 and 99.9% based on unseen data. The results indicate that this CNN model can be used as a diagnostic tool for undertaking maintenance operations.