Browsing by Author "Aguwa, J. I."

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Analysis of Safety Performance in Nigerian Construction Industry
(Nigeria Journal of Engineering and Applied Sciences (NJEAS), 2018-02-22) Kolo, D. N.,; Tsado, T. Y.,; Abdullahi, M.,; Yakubu, D.M.,; Aguwa, J. I.
The quest for the provision of adequate housing for all has translated to the increase in activities of Building construction industry in Nigeria. This growth is accompanied however with cases of poor safety performancewhich at times leads to structural failure. This study investigates and analyses safety performance in Nigerian construction industry. Investigatory survey research method (work study) was adopted to appraise the aim and objectives of the study through field and questionnaire approach. Questionnaire survey consisting of a five point Likert scale was conducted to solicit information from the respondents, and a total of 120 questionnaires were issued to construction professionals and workers on the sites visited. 92 questionnaires representing 76.67% response rate were retrieved and analysed using Statistical Package for Social Sciences (SPSS) version 21. Communalities test, Principal Component Analysis along with ANOVA were utilised for data analysis. A total of thirty-two (32) factors influencing safety performance were identified from literature, subsequently principal component analysis was utilised to reduce the list to nine (9) significant principal factors. The top nine principal factors influencing safety performance determined from the research are: Relationship between Supervisors and Employees on site, Geographical Location (Environmental Factors: Natural and Working Environment), Working Procedure, Ear defenders not worn (while working under noisy equipment), Talk by Management on Safety, Tidy Site, Safety Communication, Operatives job experience and Ladders used without being tied secured. These factors were further incorporated into a regression model. The adjusted coefficient of determination of the model was 0.98; this shows that the model has the capability of explaining 98% of variability in the data under consideration. This implies that the model is adequate in evaluating safety performance. It is therefore recommended that key industry professionals and stakeholders should channel available resources to the determined nine (9) principal safety performance factors.
Durability Characteristics of Lateritic Subgrade Treated with Iron Ore Tailings and Lime Exposed to Moisture Fluctuations
(. Nigeria Journal of Engineering and Applied Sciences (NJEAS), 2018-02-11) Mohammed, A. M.; Amadi, A. A.; Aguwa, J. I.; Kolo, D. N.
This research evaluated the durability of lateritic subgrade treated with Iron Ore Tailings (IOT) and lime exposed to moisture variations. Representative sample of the subgrade was treated with 0, 5, 10, 15, and 20% IOT and optimal lime percent (6.2%) determined through Eades and Grim pH test. Preliminary tests such as particles size distribution, Atterberg limits and compaction were conducted to characterize the mixtures while Unconfined Compressive Strength (UCS) and CBR-swell tests were carried out to access durability of the soil mixtures. Addition of lime to the soil increased the liquid limit to 45% from 36% obtained in natural soil. Similarly, the plastic limit of the lime-treated sample increased from 16 to 26% with reduced plasticity index. While the natural soil exhibited CBR of 3 and 75% for soaked and unsoaked specimens respectively, the value increased and peaked at 11 and 118% with addition of lime and 15% IOT. Durability of the soil improved with addition of IOT and lime. 15% IOT and lime treated soil recorded the best results with UCS of 240 kN/m2 and 200% Relative Volumetric Stability (RVS), which is a measure of strength loss of a soil. Similarly, swell value of 0% was recorded when the lime-IOT samples were subjected to CBR-Swell test. This shows that the lime-IOT treated samples are less vulnerable to moisture condition normally prevalent in the pavement subgrades.
Effect of Aggregate Washing on Compressive Strength of Concrete produced Using Bida Natural Stone
(Proceedings of the 2nd International Civil Engineering Conference, Department of Civil Engineering, Federal University of Technology Minna, Nigeria., 2020-02-01) Kolo, D. N.; Aguwa, J. I.; Tsado, T. Y.; Alhaji, B.; Joseph, O. F.
Concrete is the most widely used construction material in the world, second to water as the most utilised substance on earth. Coarse aggregate is an essential component in concrete production; it has effect on the workability and mechanical properties of concrete. Bida Natural Stone (BNS) which is the by-product of Precambrian deposits of Bida trough was used as coarse aggregate, utilising unwashed and washed aggregates. A total of 80 concrete cubes of 150 × 150 × 150 mm were cast and used for this study, compressive strength tests were conducted after 28 days curing. The result of physical properties test conducted proved that BNS is suitable for concrete production. The result of compressive strength tests conducted shows that concrete produced using washed aggregate results in an increase in average compressive strength of about 11.46 % when compared to that produced using unwashed aggregate. Hence, construction professionals and workers utilising this aggregate (BNS) in the Bida basin are encouraged to practice aggregate washing before concrete works.
Empirical Relationship between Compressive, Flexural and Splitting Tensile Strengths of Concrete Containing Kuta Gravel as Coarse Aggregate
(Journal of Engineering Research and Reports, 2025-02-02) Abubakar, J.; Abdullahi, M.; Aguwa, J. I.; Abbas, B. A.; Kolo, D. N.
Flexural and tensile strengths of concrete are of great importance in structural engineering. Understanding the flexural strength of concrete helps designers prevent and control development of cracks in concrete elements, ensuring durability. In addition to serviceability, shear, bond failure and flexural capacity in concrete members are directly linked to the tensile strength of the concrete. When compared to flexural and tensile strengths, determination of the compressive strength of concrete is easier to carry out in the field. It is therefore, customary to determine the compressive strength and correlate it to other strength properties. In this study, empirical relationships have been developed to relate the compressive strength to the flexural and splitting tensile strengths of concrete using Kuta river gravel as coarse aggregate. Using varying total aggregate to cement, coarse aggregate to total aggregate and water to cement ratios, 20 mixes were generated using Central Composite Design (CCD) in Minitab 21. The compressive, flexural and splitting tensile strengths of concrete samples from these mixes were determined at 28 days of age. From the strength data obtained, regression equations were developed that relate the strength properties with the aid of regression analysis tool in Microsoft Excel. The empirical models developed to predict the flexural and splitting tensile strengths of concrete from the compressive strength recorded R2 values of 1 for both models, P-values of 5.23 × 10−29 and 4.47 × 10−30, and standard errors of 0.21 and 0.06 respectively. Furthermore, residuals from the values of predicted strength properties show that there is very slight deviation between the experimental and predicted values. It was concluded that the empirical equations developed are significant, have high predictive capabilities and can be used in predicting the flexural and splitting tensile strengths of concrete.
Probability-Based Calibration of Load Duration Modification Factors for the Nigerian Grown Timber
(2023-01-02) Aguwa, J. I.; Sadiku, S.; Afolayan, J. O.; Aliyu, A.; Abubakar, M.; Kolo, D. N.
All along, load duration modification factors used in Nigeria for design of timber structures were based on BS 5268 of 2002 and this is not a good engineering practice since the strength of timber depends so much on the soil as well as on the environment. There is the need to localize the modification factors based on our environment since Nigerian grown timber is generally used for all timber structures designed and built in Nigeria. Probability-based calibration of load duration modification factors for the Nigerian grown timber was successfully carried out. The results showed significant difference between the calibrated factors and those from BS 5268 of 2002. The calibrated modification factors are; 1.25 for long-term, 1.35 for medium-term, 1.70 for short term, and 2.0 for very short-term duration. This paper recommends the use of these calibrated load duration factors based on Nigerian grown environment.
Reliability studies on reinforced concrete beam subjected to bending forces with natural stone as coarse aggregate
(Asian Journal of Civil Engineering, 2020-01-12) Kolo, D. N.; Aguwa, J. I.; Tsado, T. Y.; Abdullahi, M.; Yusuf, A.; Oritola, S. F.
This paper presents the results of structural reliability analysis of a structural element (beam) in building using First-order reliability method (FORM) to ascertain the level of safety. The natural stone (NS) which is the by-product of Precambrian deposits of the Bida trough was used as coarse aggregate: unwashed and washed aggregates were used. A total of 80 concrete cubes of 150 mm × 150 mm × 150 mm were cast and used for this study, sensitivity analysis was conducted by varying the span, depth, effective depth, area of shear reinforcement and dead load of the beam in bending. The result of the sensitivity analysis revealed that the beam utilising unwashed and washed NS are both structurally safe at a span of 3000 mm with probabilities of failure of 9.20 × 10–5 and 2.06 × 10–8 and both safe at a depth of 600 mm with probabilities of failure of 4.19 × 10–4 and 2.602 × 10–4, respectively, in bending.
Reliability Studies on Reinforced Concrete Column Subjected to Axial Load with Natural Stone as Coarse Aggregate
(NAUJournalofCivil Engineering (NAUJCVE), 2024) Kolo, D. N.; Aguwa, J. I.; Abubakar, Mahmud
This paper presents the reliability assessment of a reinforced concrete column subjected to Axial loading. Locally available natural aggregate (NA) was used in concrete production, the results of preliminary tests revealed the aggregate was adequate for concrete production. A typical column cross section of 230 × 240 × 3000mm was adopted and probabilistically assessed. First Order Reliability Method (FORM) was employed to estimate the implied probabilities of failures. The results of the sensitivity analysis showed that the reinforced concrete column is structurally safe at length, breadth and depth of 3200, 240 and 230 mm with Probability of Failures of 1.14 ×10-3, 8.45 × 10-4and 8.45 × 10-4 respectively.
Reliability Studies on Reinforced Concrete Column Subjected to Axial Load with Natural Stone as Coarse Aggregate
(Nnamdi Azikiwe University Journal of Civil Engineering (NAUJCVE), 2024-01-02) Kolo, D. N.; Aguwa, J. I.; Abubakar, M.
This paper presents the reliability assessment of a reinforced concrete column subjected to Axial loading. Locally available natural aggregate (NA) was used in concrete production, the results of preliminary tests revealed the aggregate was adequate for concrete production. A typical column cross section of 230 × 240 × 3000mm was adopted and probabilistically assessed. First Order Reliability Method (FORM) was employed to estimate the implied probabilities of failures. The results of the sensitivity analysis showed that the reinforced concrete column is structurally safe at length, breadth and depth of 3200, 240 and 230 mm with Probability of Failures of 1.14 ×10-3, 8.45 × 10-4 and 8.45 × 10-4 respectively.
Reliability-Based Code Calibration in Civil Engineering: A Critical Review
(USEP: Journal of Science and Engineering Production, 2021) Abubakar, Mahmud; Aguwa, J. I.; Abdullahi, M.; Sadiku, S.
The use of new materials and the complexities in modern civil engineering infrastructures call for a systematic attempt to find accurate design solutions. It is clear that deterministic values are not reliable and that their use in the design of civil engineering structures can lead to instant failures. Thus, the use of the probability theory to determine the most reliable value of a parameter for the design of civil engineering structures is very relevant. This work is intended to review the literature on the application of probability theory in the calibration of civil engineering design codes. Consequently, to better evaluate designs and design details, it is important to understand the techniques as highlighted herein.
Structural Reliability Studies on Pulverized Glass Powder Concrete Subjected to Bending Forces with Natural Aggregate
(Ethiopian International Journal of Engineering and Technology (EIJET), 2024-02-01) Kolo, D. N.; Aguwa, J. I.; Hadi, A. M.; Shehu, M.; Ashraf, M.L.M.
The shortage of housing and basic infrastructure in Nigeria is increasing with a continuous rise in the price of construction materials. Cement is a major component in concrete production. Its production, however, is accompanied by huge carbon dioxide emissions. This research presents the results of structural reliability analysis conducted on reinforced concrete beam produced with pulverized glass powder as partial replacement for cement with Natural aggregate (NA) as coarse aggregate by subjecting it to bending forces. First order reliability method (FORM) was employed to determine the level of safety of the beam. The result of the sensitivity analysis showed that the pulverized glass powder beam with NA as coarse aggregate is structurally safe at a span of 3000 mm and depth of 600 mm with probabilities of failure of 1.00 × 10-3 and 1.04 × 10-3 respectively.
Top Cited Articles on Structural Engineering Reliability by the Nigerian Authors
(USEP: Journal of Research Information in Civil Engineering, 2020) Abubakar, Mahmud; Aguwa, J. I.; Abdullahi, M.; Sadiku, S.; Oritola, S. F.
This study analyses the characteristics of top-cited articles on structural reliability with at least one author affiliated to Nigeria. A search in the Google Scholar database for articles published between 2010 and 2020 was carried out. From the top-cited articles, variables related to the journal, article, and authors, such as journal ranking from SCImago Journals & Country Rank (SJR), H-index, author affiliations, international research collaboration, and source of funding were collected and descriptively analysed. A sample of 25 original reports was identified from the search. The average citations per year ranged between 0.10 and 6.1. The articles were published in 20 different journals (36% found in only four journals) with five of them based in Nigeria. It was observed, that international collaboration on reliability-based researches was present in 4% of the articles, and funding was reported in just 1 article. Articles having Nigerians as first authors were reported in 100% of the articles. Articles with authors affiliated to ABU, Zaria were more frequent in the sample. A list of top-cited articles is thus, presented to provide an overview of the top-cited articles. This study could aid in supporting further analyses regarding publication, citation behaviours, research funding and international collaboration of structural reliability based researches in Nigeria.