Improved methods to predict the effective strain for the design of RC beams strengthened by FRCM composite

Fabric-reinforced cementitious matrix (FRCM) composite is a promising technique for strengthening reinforced concrete (RC) structures. A key parameter of the beam design method is the effective strain that the fibres can attain at the peak load of the beam. This study assesses the accuracy of six existing methods calculating the effective strain for the design of FRCM-strengthened beams under different failure modes. A database of 55 experimental results of FRCM-strengthened RC beams is collated. The experimental results are compared with design predictions using different effective strain prediction methods. It is found for the beams failed at fibre/mortar or mortar/concrete interface, the existing
effective strain prediction methods are not accurate, and new expressions are proposed to calculate the effective strain of fibres under these failure modes. For the beams that have failed by fibre rupture, the existing effective strain prediction methods yield sufficiently accurate results.