Damage Characteristics of Cracked TMT Reinforcement Bars

Thermo-mechanically treated (TMT) bars have rapidly replaced the conventional High Yield Stress Deformed (HYSD) bars in RCC constructions. Due to the heat treatment on TMT bars, the surface toughness of such bars gets altered. Crack initiation and propagation characteristics of such bars vary significantly from that of conventional HYSD bars. Micro-cracks usually develop in bars at bend regions or may be appearing in straight region due to accidental overloads. Prominent cracks may develop due to the 90o bends at various locations, for example at beam ends. These cracks reduce the load carrying capacity and may lead to failure at stress levels much below the yield stress. Moreover, the surface cracks at bends are larger in bars with diameters over 16 mm, amplifying their effect on the bars. Hence, it becomes imperative to study the failure characteristics of TMT bars and understand the progression of damage or cracks in the bars once the surface region has been already damaged.