Failure Propensity of GFRP Strengthen RC Beam

Abstract

Fiber-reinforced polymer has eventually become a popular choice for retrofitting and strengthening of structural entities. Hence, a need arises to know the quantitative as well as qualitative effect of these techniques on the original integrity of the concerned structural entity. In the present study, the effect of change in width to depth ratio, percentage of steel and loading intensity in a simply supported reinforced concrete (RC) beam on the maximum deflection, stress, strain energy, natural frequencies and deflections of various modes of free vibration is obtained with the help of ANSYS Workbench 19.0 software till the failure of RC beam and a comparison is sought between the original beam and a failed beam retrofitted with one, two and three layers of GFRP sheets (Epoxy S-Glass UD). A standard beam of fixed dimensions and a two point loading was first simulated in the software while comparing the results with the manual calculations of maximum deflections to ascertain the most appropriate settings of the simulation in the three dimensional analysis environment of the software. Various beams were then analyzed altering the width to depth ratio, the percentage of tension steel and the loading intensity over the beam and the results of the static as well as modal (frequency) analysis were noted including the deflections, stresses, strains, strain energies, natural frequencies of first 5 modes of free vibrations and their respective displacements. The same beams were then retrofitted with layers of GFRP sheets with their principal axis inclined at an angle of 45° with the span of the beam. The same analysis was done on the beams and the results were noted. These results are compared, and a multivariate regression analysis is performed over the results to obtain equations to testify the observations and the trends. This whole process gives a conclusion that the effect of retrofitting is insignificant for single layer GFRP while the most effective results were obtained for the case of triple layer GFRP. Deflections, stress and strain energy with their relative change across various cases are accurately related to the varying parameters through regression analysis. Frequency is also accurately related but the relative change in frequency is not well established.