Moment Capacity Charts for Strengthening of RC Beams With Near Surface Mounted FRP Reinforcement

Abstract

Near surface- mounted fibre reinforced polymer is a new technique for strengthening
 structural members beside externally applied fibre reinforced polymer (FRP) technology.
 In NSM technique, the FRP material is applied to the tension region of the member inside
 pre-prepared grooves. In externally applied FRP the debonding of the fibres is a major
 issue thus, the full utilisation of FRP material can not be achieved, and the fibres are more
 susceptible to environmental effects. With NSM FRP, these issues can be controlled more
 effectively. ACI Committee 440 [1] has presented guidelines for design and construction
 of externally FRP method for strengthening of concrete structures. Although many
 experiments have been conducted on NSM FRP in flexure strengthening of RC beams,
 no code is introduced yet. Theoretical studies to derive equations for calculating moment
 capacity of strengthened beams have been introduced but mostly require several trial
 procedures to reach the required effective strain for FRP. In this study, a moment
 capacity chart is introduced based on several assumptions in the derivation of flexure
 capacity equation. To avoid the brittle behaviour of FRP, it is suggested that the
 utilization of FRP to be limited to 70% of its ultimate capacity for CFRP, and an
 equivalent area of reinforcement is adopted for simplicity. Experimental results of other
 researchers have been verified with the proposed charts, and a good comparison of results
 have being achieved.