Effective of elastic and inelastic zone on behavior of glass fiber reinforced polymer splice sleeve Ali A. Sayadi a,⇑ , Ahmad B. Abd. Rahman b , Ahmad Sayadi c , M. Bahmani d , L. Shahryari c a Engineering Research Institute (ERI), Auckland University of Technology (AUT), Auckland, New Zealand b Faculty of Civil Engineering, Universiti Teknologi of Malaysia (UTM), 81310 Skudai, Johor Bahru, Malaysia c Department of Civil Engineering, Islamic Azad University (IAU), Shiraz Branch, Shiraz, Iran d School of Engineering, Faculty of Civil Engineering, Shiraz University, Shiraz, Iran highlights  Inelastic zone confinement is an effective method to enhance the tensile capacity.  Additional stress in the elastic zone significantly decreased the bond strength.  Position of interlocking mechanism directly affects behavior of FRP splice sleeve. article info Article history: Received 25 September 2014 Received in revised form 12 January 2015 Accepted 13 January 2015 Keywords: GFRP splice sleeve Elastic and inelastic length Bond Interlocking mechanism abstract This paper investigates the significant factors in design of splice sleeve with composite material. Factors such as position of interlocking mechanism, elastic and inelastic length of sleeve considerably affect bond strength of the bar coupling system. To assess these vital factors, an experimental study was conducted on thirty-two glass fibers reinforced polymer (GFRP) splice sleeves in tension. The specimens were pre- pared in eight batches with variation in sleeve length, number of GFRP layers, spliced steel bar diameter, and position of interlocking mechanism. The results showed that increasing the confinement pressure in elastic length of sleeve caused reduction in bond strength. Specific equations using the variables of this study were developed to predict bond strength of GFRP splice sleeve. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Design of bar coupling systems and its bond strength relies on several factors such as method of confinement [1–27], the elastic and inelastic segment [1–5], sleeve thickness [6], sleeve length[1,7], and spliced bar diameter. In order to increase confine- ment pressure and enhance bond strength, several types of con- finement method have been used by adjusting the conventional steel pipes with the spiral reinforcement [7–9], welded steel bar [7], high strength bolts [1–3] ribbed hollow section [10], and mod- ifying the steel pipe to tapered shape [11–12]. In addition, effects of angle of sleeve surface [6,11], length and diameter of shear key bar [7,11], pitch distance and length of spiral reinforcement [7] on bond strength of splice sleeve have so far been studied. Moreover, to overcome the problem of corrosion, non-corrosive materials such as aluminum tubes [13,14] and fiber reinforced polymer [3–5,6,15] are used in place of steel pipe to provide the appropriate confinement pressure. Bond strength between the steel bar and the surrounding con- crete is mainly obtained by the contribution of chemical adhesion, frictional resistance, and mechanical interlock between steel bar ribs and concrete [28–31]. At the same time, the bond strength of mechanical splice sleeve is affected by two more factors, namely the position of interlocking mechanism and its relation with elastic and inelastic region of mechanical steel splice sleeve [1]. Providing additional confinement in the inelastic region of splice sleeve sig- nificantly increases the bond strength, whereas extending the con- finement pressure out of this region (elastic region) causes bond failure in mechanical steel splice sleeve [1]. In order to evaluate the effect of elastic and inelastic region on the behavior of glass fiber reinforced polymer splice sleeve, an experimental study was conducted on thirty-two GFRP splice sleeves in eight groups by considering the variables in sleeve thick- ness, steel bar diameter, position of interlocking mechanism, and sleeve length [3–5]. http://dx.doi.org/10.1016/j.conbuildmat.2015.01.064 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: ali.a.sayadi@gmail.com, asayadi@aut.ac.nz (A.A. Sayadi). Construction and Building Materials 80 (2015) 38–47 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat