Cracking Behavior of CFRP Laminate-Strengthened RC Beams with Premechanical and Postmechanical Environmental Damage

Abstract

The main objectives of this study are to investigate the effects of three types of predamage and postdamage on the cracking behaviors of carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete RC beams and to develop a rational methodology for predicting the average stabilized crack spacing. The predamage is induced by either sustained loading only or by the combination of sustained loading and corrosion. The predamage involved a sustained loading with an anchor tightening system, an electrochemical process to accelerate the migration of chlorides from an external electrolyte into the tested beams, and a wetting–drying cycle process with a controlled current to accelerate the corrosion of the reinforcing steel bars in the tested beams. The postdamage was induced by wetting–drying cycles. A loading test was conducted to determine the cracking behaviors of stabilized flexural cracks in the CFRP-strengthened beams with or without damage. The crack patterns, crack spacings, and test beam widths were recorded and compared, and the related mechanism was discussed. It was found that after CFRP strengthening, the effect of predamage or postdamage on the crack spacing and width is not as distinct as in the unstrengthened cases. The sustained loading predamaged beam showed insignificant differences in crack spacing and width compared to beams without predamage. Subsequently, a model capable of evaluating the crack behaviors of CFRP-strengthened beams with or without damage was developed. The analytical approach is based on equilibrium and compatibility equations to elucidate the average stresses of concrete and the CFRP laminate of a CFRP-strengthened beam element.