Experimental study of corrosion effects on pulling force of hook bars in external beam-column connections

Abstract

The external beam-column connection in concrete structures is particularly important because it is necessary to secure the reinforcement bars of the beam that are embedded within the column, which are often formed as a 90° hook. The attack of chloride ions is also one of the most dangerous damages that affect constructions and reduce their service life. Hence, it was necessary to study the effect of corrosion resulting from chloride ion attack on the strength of hook bars. To achieve this purpose, 26 specimens were designed with various variables, including the corrosion level of the reinforcement bars, compressive strength of the concrete, specimen loading, and the spacing between the stirrups relative to their diameter (S/D). The specimens were subjected to accelerated corrosion in the laboratory using the current density method by applying 0.35 mA/cm2 for 21 and 58 days. The experimental results showed that corrosion of the reinforcing bar in the joint weakens the mechanical behavior of rebars by reducing their strength and the bond between them and the concrete. The effect of the compressive strength of the concrete, specimen loading, and S\\D on the hook pulling force for corroded and non-corroded specimens has been observed, and they also affected the determination of the level of corrosion. Equations have been proposed to develop Faraday's law and determine the pulling force of a hook bar. The proposed equations yielded results that closely matched those from the experimental test.