Experimental study of reinforced concrete beam attenuation changes with FRP sheets

Abstract

This article reviews the natural frequency and damping in reinforced concrete beams strengthened with CFRP sheets in various stages of cracking. It is  based on static load tests on beams with Vdynamyky and sheet tensile strength in the area and also carried beams without strengthening. For this purpose, six concrete beams were tested under static loads. This has been continued  step by step to reach the final stage of failure. In these experiments, two shots were used as reference beam. Also  the two beams reached the half final load and  were reinforced with a layer of CFRP sheet. Other examples reached about 75% of ultimate load when the loads were reinforced with two layers of CFRP sheets.

 After each load step, and creating damage, dynamic testing (modal) hanging on the beams was performed at the natural frequency and damping rate of the result obtained in each step. The results of included reduction in frequencies in all the beams after loading and cracking which might the result of reductions be of beam stiffness. The reduction continued in all the  steps before loading. After strengthening the beams with CFRP fibers, natural frequency beams also increased due to increased stiffness.