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The quality of steel rods used in structural applications has been subjected to continuous scrutiny by researchers in Nigeria. In this article, the experimental data on the chemical and mechanical properties of steel rods from collapsed building sites and local steel plants have been reported. The chemical composition consisting of carbon, manganes...
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... other samples of steel rod were obtained from two steel plants in Osun State, Nigeria. Steel rods of 12 and 16 mm diameters were collected from steel plant A and tagged as A12 and A16, respectively. Steel rods of 10, 12, and 16 mm were collected from steel plant B and tagged as B10, B12, and B16, respectively. Examples of these rods are shown in Fig. ...
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... In addition to weak enforcement, a lack of material testing leading to the deployment of defective materials has been fingered as a cause of building collapse. [11] Post-accident evaluation of construction materials from building collapse sites, according to a study [11] , ...
... In addition to weak enforcement, a lack of material testing leading to the deployment of defective materials has been fingered as a cause of building collapse. [11] Post-accident evaluation of construction materials from building collapse sites, according to a study [11] , ...
... Although the data is uncertain, several studies have noted the general trend of unexpected collapse of buildings leading to fatalities [1][2][3]. An area of research that has received considerable attention in the past few years is the study of the strength of reinforcement steel available in Nigerian markets [4][5][6]. Such studies are especially important given that steel is the primary load-resisting element in reinforced concrete. ...
... A total of 18 studies on the strength of steel reinforcement were found, with the earliest date being 2010 [4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Although they have been concentrated mainly in Lagos and the surrounding South-Western Nigerian states (around 50%), there have been studies in a fair number of places too. Figure 1 shows this geographic spread throughout the country. ...
... However, a major shortcoming of these studies is the absence of the characteristic strength values of the tested steel samples. In one case, this was due to omission [6], but in all other cases, a conflation was made of the characteristic strength with the mean strength [4,5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. This has given an incorrect picture of the state of affairs. ...
There has been increasing concern in recent years over the structural integrity of construction in Nigeria. Reinforced concrete is the primary structural material in the country, so the strength of the steel reinforcement has become a major target for scrutiny. This study reviews the reported literature on reinforcing steel strengths from tests carried out in Nigeria between 2010-2021. The characteristic strength of steel is the basis for the design of steel reinforcement in both the Eurocode and British Standards used for design in Nigeria. However, it is noted that in every case, the characteristic strength results are missing or erroneously reported. A total of 18 studies are found, and the raw data for each study is analysed to derive the characteristic strength results. An average characteristic strength of 342.4 MPa is found from all the studies, lower than the 400 MPa and 500 MPa minimums assumed in the Eurocode and British Standards respectively. The finding here indicates that the widespread methodology around interpreting the tensile testing of steel reinforcement in Nigeria needs revisiting.
... Following the collapse of buildings in Nigeria, researchers have concluded that one of the main causes is that the properties of some steel bars used in construction were not up to standard [8]- [15]. The percentages of chemical elements in steel have an effect on its properties [4]. ...
... This brittleness was due to higher contents of harmful Sulphur and Phosphorus. In their study, Adeleke et al. [12] compared the elemental composition of the selected samples of steel rods with BS 4449, reported that 90.9%, 36.4%, and 72.7% of the samples did not conform to the maximum limits of Carbon, Sulfur, and Phosphorus respectively. Besides, only Copper was 100% compliant out of the tested samples. ...
... The criteria employed in each company during the production of these steel bars products can also affect the conformance to the standards. The trend of results obtained in this work was supported by many researchers [4,6,8,11,12]. Figure 3 shows the percentage by mass of Phosphorus in different brands. For SON and BSI standards, all brands complied with permissible values of Phosphorus except Brands 1, 6A, 11A, and 18 of ordinary steel rods. ...
... Two of the TMT Brands (6B and 20A), 55% of ordinary, all locally rolled with imported billets, and all imported steel rods complied with specifications for product check condition. Odusote and Adeleke [11], and Adeleke et al. [12] also detected high content of Phosphorus using the same standards in their experimental research. specified limit. ...
Nigeria is presently facing the challenges of collapsing buildings and bridges due to substandard materials used as reinforcement products. The increasing use of scraps as feedstock for the production of reinforcing steel bars by steel rolling mill companies has adversely affected the quality of rebars in Nigeria. This research study aimed to appraise the chemical properties of selected brands of steel rebars of Nigeria. Thirty selected brands of rebars were sourced from the six geopolitical zones in Nigeria, and their chemical compositions were analysed for level of compliance with five selected standards (SON, BSI, ASTM, AISI, ISO). The chemical composition test was performed using Optical Light Spectrometric methods. One way analysis of variance (ANOVA) test was performed using SPSS version 20 to examine whether significant differences exist or not in mean chemical composition for the different categories of selected steel rods. Statistical analysis shows a significant difference (P < 0.05) in chemical composition and compliance level between the different types of selected steel rods. The imported steel rods recorded the highest mean (μ= 101.4) in terms of chemical composition and compliance, followed by locally rolled from imported billets (μ =101.2), TMT steel rods (μ =101.0), and ordinary steel rods (μ =100.6). Concerning CEV1 and CEV2, it was observed that all the brands were fully compliant within the maximum permissible ranges given in the local, foreign and international standards except an ordinary steel bar of Brand 16, which has value beyond the specified limits of CEV1. This study also shows that all imported and 77.8% of locally-rolled steel bars are low-carbon steel as specified by the selected standards.
... In these studies, the samples were collected for a specific steel grade, meaning that the impurity content was kept within the defined limits and is not representative for a variability of rebar grades. Contents for rebars produced from local scrap in Ethiopia (Atsbaha, 2017), Ghana (Kankam, 2004), and Nigeria (Adeleke et al., 2018) have representative patterns of impurities mixing. Even though steel production in these three countries is very limited and relies on the import of steel products (Worldsteel, 2016), the local production of rebars reflects the local scrap supply and recycling system efficiency. ...
The accumulation of impurities in the recycling of steel impacts the quality of secondary steel. Understanding impurity levels is crucial in the context of the proliferation of circular economy policies, expected high recycling rates, and growth of scrap consumption. By assuming the accumulation of impurities to be equal worldwide, the understanding of the extent and variation of the mixing and accumulation was limited in previous studies, and the factors influencing those variations were not considered. This is a first cross‐national comparison of impurity accumulation in recycled steel. In this study, the copper, tin, nickel, chromium, and molybdenum content was analyzed in over 500 samples of electric arc furnace rebars from China, Japan, Vietnam, Ukraine, and the Netherlands (representing northwestern Europe) with an optical emission spectrometer. The impurity content in rebars represents the content of impurities accumulated in steel scrap in the countries studied. The measured content of impurities was then used to determine the factors influencing the accumulation of those impurities. It was revealed that the recycling technology, the presence of a market for recovered metals, the quality of the material input, steelmaking practices, and the management of byproducts derived from a legislative or economic context played a role in the impurities content. By communicating on scrap chemical content, the collaboration between the recycling and steel industries could be enhanced in terms of matching the demand and supply and facilitating an increase in the scrap share in steelmaking.
... Currently, most of the reinforcing steel bars used in the construction industries in Nigeria are produced majorly from scraps. Several researchers [2,[5][6][7][8][9][10] have investigated causes of collapse of building in Nigeria, and some have worked on improving the mechanical properties of the reinforcing steel bars through heat treatment [11][12][13]. One of the major causes reported is that the structural properties of some of the reinforcing steel bars used in the actual constructions do not conform to relevant standards. ...
Al-Zn-Cu alloys are widely used in various manufacturing industries. However, the need to improve the mechanical strength of the alloy while the overall weight is reduced has continued to be a major concern. Therefore, the present study investigates the influence of magnesium addition on mechanical properties and microstructure of Al-Zn-Cu alloy. Al-Zn-Cu alloy was modified by adding Mg in the range of 0.5 to1.5wt.% and prepared by sand casting. The cast Al-Zn-Cu-Mg alloy samples were heat-treated at 460 for 2 h, quenched in water and then age-hardened at 160oC for 5 h. Tensile, impact and hardness tests were carried out on the as-cast and heat-treated Al-Zn-Cu-Mg alloy samples. The surface
morphology of the as-cast and precipitation hardened samples were observed using optical and scanning electron microscopy. The highest tensile strength (178.038N/mm2
) and hardness value (42.49 HB) were obtained from the addition of 0.33 wt.% Mg and 0.001wt.% Mg to Al-18Zn-2Cu alloy, respectively. The presence of coarse reinforcing intermetallic phases was observed in the as-cast samples compared to the well-distributed fine grain intermetallic phases in the precipitation hardened
samples. It can be concluded that addition of magnesium has a positive impact on the mechanical strength of Al-Zn-Cu-Mg alloy while the precipitation hardening process eliminates micro-segregations in the microstructure of the alloy, thus improving the mechanical properties of Al-Zn-Cu-Mg alloy.
... Currently, most of the reinforcing steel bars used in the construction industries in Nigeria are produced majorly from scraps. Several researchers [2,[5][6][7][8][9][10] have investigated causes of collapse of building in Nigeria, and some have worked on improving the mechanical properties of the reinforcing steel bars through heat treatment [11][12][13]. One of the major causes reported is that the structural properties of some of the reinforcing steel bars used in the actual constructions do not conform to relevant standards. ...
Steel bars are important engineering materials for structural application. In Nigeria, due to incessant building collapse occurrences, it is important to further investigate some of the mechanical and chemical properties of reinforcing steel bars produced from scrap metals in order to ascertain their compliance with the required standard. Three diameters (10, 12 and 16 mm) of the reinforcing steel bars were chosen from each of the eight steel plants (A–H). Chemical composition analyses and mechanical tests (yield strength, ultimate tensile strength and percentage elongation) were performed using optical emission spectrometer and Instron Satec Series 600DX universal testing machine, respectively. Hardness values of the samples were obtained by conversion of tensile strength based on existing correlation. The results showed that carbon contents, hardness values, yield and ultimate tensile strengths of some of the steel bars were found to be higher than the BS4449, NIS and ASTM A706 standards. The steel bar samples were also found to possess good ductility with samples from steel plants C and D. By observation, all the 12 mm steel bars from steel plants A to H met the required ASTM and BS4449 standards except samples from plant G. This study revealed that most of the investigated reinforcing steel bars have reasonable yield strength, ultimate tensile strength, ductility and hardness properties when compared with the relevant local and international standards. Therefore, they are suitable for structural applications where strength and ductility will be of paramount interest.
... The brittleness could be because of the formation of FeS and Fe 3 P compound (Sanmbo et al. 2009). Adeleke et al. (2018) evaluated the mechanical behavior of 10, 12, and 16 mm diameter rebar. The average yielding strength for the 10, 12, and 16 mm re-bars was about 410.59, 404.62, and 373.13 MPa, respectively, while the average ultimate tensile strength for the rebars was 667.73, 544.80, and 556.16 ...
... The literature reviews above have indicated that some studies performed on the mechanical properties of reinforced steel bars at various testing conditions (Adeleke et al. 2018;Sanmbo et al. 2009;Alabi and Onyeji 2010;Kareem 2009;Ejeh and Jibrin 2012). However, there are limited numbers of studies on steel bars of 8 mm and 12 mm (Alo et al. 2017;Arum 2008;Rao et al. 2016, Ocheric andIbe 2017). ...
... There were good agreements with some other works carried out previously (Alo et al. 2017;Adeleke et al. 2018, Charles andMark 2002). However, the present study indicated that average YS and UTS were about 46% and 16% higher for three diameters (10, 12 and 16 mm) than that of recent study (Adeleke et al. 2018). Means YS for 10, 12 and 16 mm bars were measured at 490, 370 and 340 MPa (Charles and Mark 2002), which were quite lower than our results because corresponding values the same diameters were about 608, 563, 566 MPa, respectively. ...
This paper presents the annual report of the mechanical properties of ribbed reinforcement bars from construction sites taking projects as the case in and around Amhara, Ethiopia. Both imported and locally produced re-bars are used in the analysis without consideration of their varieties in the quality of the two sources. This paper focused on only with reinforcement bars of diameter 8, 10, 12 and 16 mm that accounted for 67% of the total tests. Using Universal Testing Machine, strength properties such as ultimate tensile strength (UTS), yield strength (YS), percentage elongation at fracture (%) and linear mass density property (kg/m) of steel reinforcing bars were analyzed for rebar diameters of 10, 12, 8 and 16 mm. Moreover, the results were analyzed by one-way analysis of variance (ANOVA). The results showed that the mean values of YS and UTS of all diameters surpassed the standard values recommended limit set by BS449: 1997 and ASTMA706. In addition, the mean values of percentage elongations for all tested steel products surpassed the 12% limit recommended by BS 449, 10% by ASTM A706 for all diameters. However, the mean mass per length values for 8, 10, 12 and 16 mm were below standard values set by ASTM A615/A615M. Furthermore, ANOVA indicated that the reinforced bars appeared to be dissimilar in terms of UTS and YS with 95% confidence, but the reinforced bars were similar to the elongation percentage.
The process monitoring techniques play an essential role to improve the overall performance of processes. The control chart is an essential monitoring tool used to detect changes in the process parameters. The Shewhart charts are famous for detecting larger shifts, while exponentially weighted moving average (EWMA) and cumulative sum (CUSUM) control charts are famous for detecting small‐to‐moderate shifts. The separate control schemes are required for the quick identification of the changes in the process parameters because sometimes testing is too expensive or time taking and a practitioner may not afford any kind of defects or loss. With this motivation, the dynamic feature of this article is to introduce an efficient sequential probability ratio test (SPRT) decision‐based Tukey CUSUM design. The performance of the proposal is judged by using several run lengths (RLs) performance measures such as average, median, standard deviation, and percentile RLs. Based on the comparative analysis, it is revealed that the proposed chart offers more sensitivity towards the changes in process location than its competitor's charts for several probability models. The study proposal may find applications in packaging, manufacturing, decision‐making, finance and economics modeling, image processing and automation. A case study from steel rods manufacturing is included to demonstrate the application of the proposed design.
The yield strength of steel is an important property in designing a steel component. The maximum load that material can sustain without undergoing permanent deformation is represented by yield strength. A robust model is purposed, which can accurately predict the
yield strength of different steel grades, based on the varying chemical composition of steel from the employed database. The dataset consisting of the chemical composition and experimental yield strength of steel rods from a collapsed building sites. MATLAB® was
used to generate a regression model such as multivariate regression and linear regression, to predict the yield strength values for different steel grades. A comparative study among the different regression models for RMS error, Max error, and highest accuracy is discussed in this paper.
