Investigation of shear compression failure behavior of reinforced concrete short columns with low strength concrete

Shear strength deficiency of captive columns is one of the most important deficiencies in the damage of the building during the earthquake. Our experience gained from the earthquakes that we have experienced in recent years shows that common deficiencies for these members are sufficient stirrups, insufficient cross-sections, low strength concrete, change in the support conditions of columns where all these deficiencies cause decrease in shear strength of columns. In this study, the behaviors of such columns were investigated experimentally. For this purpose, four specimens were produced and tested to represent the weaknesses of the existing columns. Two equivalent specimens were designed to be sufficient in terms of transverse reinforcement according to TS 500 and TBDY (2018). The remaining two equivalent specimens are designed to have inadequate transverse reinforcement ratio according to regulations and standards. Within the scope of the study, firstly, two reference specimens where one of them is sufficient according to the transverse regulations and while the other was not, were tested and the existing behavior was examined. Then, the remaining two specimens were retrofitted with perforated steel plate and repair mortar in the shear span area. Thus, the retrofitted specimens were compared with the reference specimens in terms of shear strength and ductility. The specimens were subjected to constant axial load in vertical and increased monotonic loads in the horizontal directions. As a result of these experiments, important information on the behavior of captive columns with such weaknesses was obtained. In order to follow the behavior of the columns step by step and also can be able to follow the progress of the damage, the loading was increased in a static and monotonic manner. As a result, it was observed that the specimens produced had a brittle failure with shear damage as expected. As a result of the work on, important data accumulation and information about behavior of such columns has been obtained. The failure of the reinforced specimens were caused by the debonding and failure of the steel plates due to the crushing of the internal concrete. Key Words: Reinforced concrete, low strength concrete, captive column, inadequate stirrup.