Abstract—Structural failures occur due to a number of reasons. These may include under design, poor workmanship, substandard materials, misleading laboratory tests and lots more. Reinforcing steel bar is an important construction material, hence its properties must be accurately known before being utilized in construction. Understanding this property involves carrying out mechanical tests prior to design and during construction to ascertain correlation using steel testing machine which is usually not readily available due to the location of project. This study was conducted to determine the reliability of reinforcing steel testing machines. Reconnaissance survey was conducted to identify laboratories where yield and ultimate tensile strengths tests can be carried out. Six laboratories were identified within Ibadan and environs. However, only four were functional at the time of the study. Three steel samples were tested for yield and tensile strengths, using a steel testing machine, at each of the four laboratories (LM, LO, LP and LS). The yield and tensile strength results obtained from the laboratories were compared with the manufacturer’s specification using a reliability analysis programme. Structured questionnaire was administered to the operators in each laboratory to consider their impact on the test results. The average value of manufacturers’ tensile strength and yield strength are 673.7 N/mm 2 and 559.7 N/mm 2 respectively. The tensile strength obtained from the four laboratories LM, LO, LP and LS are given as 579.4, 652.7, 646.0 and 649.9 N/mm 2 respectively while their yield strengths respectively are 453.3, 597.0, 550.7 and 564.7 N/mm 2 . Minimum tensile to yield strength ratio is 1.08 for BS 4449: 2005 and 1.15 for ASTM A615. Tensile to yield strength ratio from the four laboratories are 1.28, 1.09, 1.17 and 1.15 for LM, LO, LP and LS respectively. The tensile to yield strength ratio shows that the result obtained from all the laboratories meet the code requirements used for the test. The result of the reliability test shows varying level of reliability between the manufacturers’ specification and the result obtained from the laboratories. Three of the laboratories; LO, LS and LP have high value of reliability with the manufacturer i.e. 0.798, 0.866 and 0.712 respectively. The fourth laboratory, LM has a reliability value of 0.100. Steel test should be carried out in a laboratory using the same code in which the structural design was carried out. More emphasis should be laid on the importance of code provisions. Keywords—Reinforcing steel bars, reliability analysis, tensile strength, universal testing machine, yield strength. Wasiu O. Ajagbe is a senior lecturer with the Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria. (e-mail: ajagbewas@gmail.com) Habeeb O. Hamzat was formerly a master’s student with the Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria. (e-mail: hoyhamzat@gmail.com) Waris A. Adebisi is currently a master’s student with the Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria. (corresponding author, phone: +2349033171704; e-mail: warislg@gmail.com) I. INTRODUCTION UILDINGS, like all other structures, are designed to support certain intended loads without deforming excessively. The aim of the building design is to meet its owner’s requirements functionally and to satisfy safety requirements. No part of such building should pose a hazard to its occupants [4]. However, there have been previous newspaper reports (such as that of Synagogue Church of All Nations building collapse around Ikotun Egbe area of Lagos state on 12 September, 2014,) of building collapses and structural failure at a time or the other due to a number of reasons. Structural failures can be attributed to factors ranging from poor workmanship, inadequate design, use of substandard materials, corruption, government policies etc. Reference [7] attributed building failure to the following; design faults (50%), faults on construction site (40%) and product failure (10%). Reference [3] on the other hand categorized the following as major causes of structural failures: environmental changes, natural and man-made hazards; improper presentation and interpretation in the design output. These failures can be partial or total in nature. The two principal materials used in reinforced concrete structures are concrete and reinforcing steel bars to complement each other in areas of compressive and tensile strengths [6]. During structural design, it is normally assumed that the materials (concrete and steel) will attain a certain strength which is used to carry out the desk design from which construction drawings are prepared. It is therefore necessary that concrete and steel reinforcement bars undergo compressive and tensile strength tests to determine their standard strength which must conform with the initial assumed design strength. The compressive and tensile strengths are important mechanical properties of these major materials (concrete and steel reinforcement) that make up reinforced concrete structures [9]. Tests are however carried out to ascertain these properties after an assumption has been made during the desk design. The accuracy of both the compressive and steel tensile strength tests depends greatly on the reliability of the machine used for test. Since the result obtained from the testing machine will be adopted in the structural design, hence such machine must be reliable to a very large extent. The value of the characteristic strength which is of utmost importance for structural design can only be obtained using steel testing machine. If the machine to be used for the test is faulty, the result will be non-reliable and tells a lot on the result of the design and definitely on the construction and vice versa. In Result Validation Analysis of Steel Testing Machines Wasiu O. Ajagbe, Habeeb O. Hamzat, Waris A. Adebisi B World Academy of Science, Engineering and Technology International Journal of Mechanical and Mechatronics Engineering Vol:12, No:11, 2018 1029 International Scholarly and Scientific Research & Innovation 12(11) 2018 Digital Open Science Index, Mechanical and Mechatronics Engineering Vol:12, No:11, 2018 waset.org/Publication/10009749