Strength model of FRP confined concrete columns based on analytical analysis and experimental test Mahfoud Touhari Department of Civil and Mechanical Engineering, Faculty of Sciences and Technology, Khemis Miliana University, Khemis Miliana, Algeria, and Ratiba Kettab Mitiche Department of Civil Engineering, National Polytechnic School, Algiers, Algeria Abstract Purpose – Covering a fiber-reinforced concrete column ( fiber reinforced plastic (FRP)) improves the performance of the column primarily. The purpose of this paper is to investigate the behavior of small FRP concrete columns that are subject to axial pressure loading, in order to study the effect of many parameters on the effectiveness of FRP couplings on circular and square concrete columns. Design/methodology/approach – These parameters include the shape of the browser (circular and square), whole core and cavity, square radius of square columns, concrete strength (low strength, normal and high), type of FRP (carbon and glass) and number of FRP (1–3) layers. The effective fibrillation failure strain was investigated and the effect of effective lateral occlusion pressure. Findings – The results of the test showed that the FRP-coated columns improved significantly the final conditions of both the circular and square samples compared to the unrestricted columns; however, improvement of square samples was not as prominent as improvement in circular samples. The results indicated that many parameters significantly affected the behavior of FRP-confined columns. A new model for predicting compressive force and the corresponding strain of FRP is presented. A good relationship is obtained between the proposed equations and the current experimental results. Originality/value – The average hoop strain in FRP wraps at rupture in FRP-confined concrete specimens can be much lower than that given by tensile coupon tests, meaning the theoretical assumption that the FRP- confined concrete cylinder ruptures when the FRP material tensile strength attained at its maximum is not suitable. Based on this observation, the effective peak strength and corresponding strain formula for FRP concrete confined columns must be based on the effective hoop rupture strain composite materials. Keywords Compressive strength, Effective circumferential failure, Effective lateral confining, FRP composite, Ultimate strain Paper type Research paper Nomenclature f co Ultimate strength of unconfined concrete f cc Ultimate strength of FRP-confined concrete f l Effective lateral confining stress ε co Ultimate strain of unconfined concrete ε cc Ultimate strain of FRP-confined concrete ε frp,u Ultimate circumferential strain in the composite jacket ε h,rep Effective failure strain of FRP-confined concrete k e Area confinement effectiveness coefficient E frp Tensile modulus of FRP ρ frp FRP volumetric ratio k ef Effective FRP strain factor k mef Mean effective FRP strain factor Ø Angle of internal friction of concrete t f Thickness of FRP composite D Diameter of the concrete core International Journal of Structural Integrity Vol. 11 No. 1, 2020 pp. 82-106 © Emerald Publishing Limited 1757-9864 DOI 10.1108/IJSI-04-2019-0040 Received 22 April 2019 Revised 22 April 2019 Accepted 24 June 2019 The current issue and full text archive of this journal is available on Emerald Insight at: www.emeraldinsight.com/1757-9864.htm 82 IJSI 11,1