Flexural behavior of reinforced concrete beams externally strengthened with Hardwire Steel-Fiber sheets R.A. Hawileh ⇑ , W. Nawaz, J.A. Abdalla American University of Sharjah, Department of Civil Engineering, P.O. Box 26666, Sharjah, United Arab Emirates highlights  Beams were strengthened externally-bonded HSF sheets.  Sheets were attached using epoxy adhesive.  Two different densities of HSF sheets are used.  Test results showed an increase up to 60% over control specimen. article info Article history: Received 27 February 2017 Received in revised form 19 March 2018 Accepted 22 March 2018 Keywords: Reinforced concrete Beams Hardwire Steel-Fiber sheets Strengthening Ductility abstract Fiber Reinforced Polymers (FRP) has been used predominantly as externally-bonded strengthening mate- rials using epoxy adhesives. Recently emerged Hardwire Steel-Fiber (HSF) sheets have desirable charac- teristics that made them attractive candidates as strengthening materials. The literature lacks information on the flexural performance of RC beams when externally strengthened with HSF composite sheets. This paper presents an experimental investigation consists of seven reinforced concrete (RC) beams strengthened in flexure with externally-bonded HSF sheets using epoxy adhesives. Two types of HSF sheets with medium and high-cord densities of 4.72 and 7.87 cords/cm were investigated. Four- point bending tests were conducted and the load-deflection and strain response data at the beams’ mid-span section were recoded until failure of the beam specimens. The test results were compared with a control unstrengtherned beam specimen. Experimental results showed an increase in the load-carrying capacity of the strengthened specimens ranging from 29% to 62% over the control unstrengthened spec- imen. However, the ductility of the strengthened specimens was less than that of the control specimen and all strengthened specimens failed in flexure by delamination of the concrete cover. The ultimate load-carrying capacity of the tested specimens was predicted using the guidelines of ACI 318-11 and ACI 440.2R-08, while mid-span deflection response curves were predicted using ACI 318-11 guidelines. The predicted results were in close agreement with the experimentally measured ones. It has been con- cluded that HSF sheets, externally-bonded with epoxy adhesives to the soffit of concrete beams, can serve as effective flexural strengthening composite material. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction Ageing and deterioration of existing reinforced concrete (RC) structure have emerged as some of the major issues that need to be addressed during by the construction industry in the last few decades. RC structures are deteriorating over the years due to many reasons such as construction faults, design or detailing errors, corrosion of steel reinforcement, increase in live loads [1–7]. The rehabilitation and strengthening of structural members is currently a major concern for researchers and engineers. Over the last few decades, several investigations have been conducted on external shear and flexural strengthening of RC beams by using different types of strengthening materials and techniques [1–7]. Bond strength and bond durability of externally bonded strength- ening material had also been studied [8–11]. In the early 1940 s, steel plates have been utilized for strengthening RC beams in flex- ure [12]. However, despite the increase in the load-carrying capac- ity of RC beams, major drawbacks were shown by the exposed steel plates such as corrosion, high interfacial shear stresses at the plate ends, premature debonding, and heavy weight of plates [13,14]. The limitation of steel plates as external strengthening materials, https://doi.org/10.1016/j.conbuildmat.2018.03.225 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: rhaweeleh@aus.edu (R.A. Hawileh). Construction and Building Materials 172 (2018) 562–573 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat