Copyright © 2018 Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (4.20) (2018) 229-234 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research paper Experimental Study of Replacement the Tension Reinforcing Bars in Concrete Beams by Steel Pipes Labeeb Saadoon Al-Yassri 1 *, Alaa Mahdi Al-Khekany 2 , Hajer Satea Abbas 3 1 Factuality of Engineering, University of Al-Qadisiyah, Iraq: 2 Factuality of Engineering, University of Al-Qadisiyah, Iraq 3 Al-Esraa University, Baghdad, Iraq. Authors Tel.: +964 781 6764 606, +964 781 0034 028 *Corresponding author E-mail: Labeeb.Husein@qu.edu.iq. Abstract Structures designed with reinforced concrete beams are used extensively in construction projects because of their functional and economic features. In this research, tested concrete beams were cast and reinforced with small diameter steel pipes and /or steel bars as flexural reinforcement to study the effect of this configuration of reinforcement on the structural behavior of reinforced concrete beams. The idea of this research involves performing and testing of four reinforced concrete beams reinforced by small diameter steel pipes with different percentages of replacement with traditional steel bars (0%, 33%, 66% and 100%). The experimental results showed that using of steel pipes reduces the flexural capacity by (2.7, 18.3, 37.5%) if compared with traditional steel bar according to the replacement percentages of (33%, 66%, and 100%) respectively. Moreover, the stiffness of beams reinforced with steel pipes (fully or partially) decreased as a result of the difference in the mechanical properties between steel bar and the steel pipe and also, the bond strength reduction between the smooth steel pipe and surrounded concrete. Keywords: Reinforced concrete beam, steel pipes, steel bars, flexural strength, mode of failure 1. Introduction In contemporary structural construction, transverse openings in strengthening concrete beams are regularly supplied for the passageway of utility pipes and ducts. These ducts are essential for the purpose of accommodating necessary facilities like electricity, water supply, telephone, and Internet. They are typically positioned under the beam soffit and for visual reasons, are enclosed by a suspended ceiling for generating a dead space. On every floor, this dead space height inserts the total building height in accordance with the amount and depth of ducts. For that reason, the web openings assist the civil engineer to decrease the structure height, particularly with respect to tall buildings, leading to an extremely cost-effective project [1-4]. All-inclusive reported papers concerning perforated and continuous RC beams with variable opening sizes, outlines, and positions for monotonic loading are explained in the literature as in [5–11]. 2. Opening Classification Here, we will detail about reinforced concrete beams with web openings using opening’s size, outline and location. Openings can be categorized as small or big openings and the finest opening location is in accordance with its size. Web openings were found to take numerous forms like rectangular, circular, triangular, diamond, trapezoidal and uneven outlines. On the other hand, rectangular and circular openings are the most conventional ones practically [12]. Depending on opening sizes, various scholars adopt the terms ‘‘small’’ and ‘‘large’’ with no any illustration about any clear-cut demarcation line. Small openings can be described as square, circular or almost square in outline [13]. Vice versa based on Somes and Corley [14], a circular opening is feasibly been as large if its diameter goes above 0.25 times the beam depth (h) and its length is less than or equivalent to its depth (d). Accordingly, the beam action can be presumed to prevail. Consequently, the investigation and project of a beam with small openings possibly take the comparable course of action as in solid beam. Small openings are, thus, defined as openings which are small enough and situated in such approach that a strut-tie model (STM) is capable of jumping over the openings without causing extra vertical or horizontal struts in the chords above and below the openings [15]. Large openings can be defined as an opening that requires additional vertical and horizontal struts in the chords above and below the opening. An opening is assumed large in the case of its depth (d) or diameter (D) is bigger than 0.25 times the depth of the beam (h) and its length (ℓ) is greater than its depth (d) for the reason that the outline of such openings decreases the strength of the beam and the beam type behavior will be, according to Somes and Corley [14]. According to the aforementioned analysis, it is obvious that openings possibly have numerous forms and the nonstop openings along the span of the beam have not been studied extensively yet. The authentic category and position of an opening should be obvious given before the project requirement phase. 3. Research Significance A comparatively huge number of researches were examined the diverse foremost influences involved in the problem: cross-