The Bond Strength on Over Lapping Bars Using Pullout Test

The behavior of reinforced concrete structures depends on sufficient bond strength between concrete and reinforcing steel. The perfect bond between the reinforcement surface and the concrete makes the transfer force work well. In this experiment, several forms of bars overlapped in the concrete and then tested pullout directly. This experiment is to get the tendency of the bond stress patterns that occur in overlapping bars. Another result of the study is the failure pattern of each specimen. The specimen size is 150×150×150 mm. In the center of the concrete cube is rib two overlapped bars. The reinforcement used plain and two ribs types of bars surface. The compression of concrete used is a minimum of 25 MPa. Furthermore, the specimen was subjected to a pullout test loaded in stages with 22 kN/minute speed. Loading stopped after the sample has collapsed. The pullout test uses the ASTM C234-91a standard. The failure pattern of plain reinforcement specimens with diameters of 12 mm, 16 mm, and 19 mm is a pullout or a slipped. The specimen with deform bar diameter 13 mm, 16 mm, and 19 mm occurs in splitting failure. The pullout test result, all samples in connection not yielded yet. The results show that the higher the bar diameter's development length, the higher the bond strength. The bond stress of the plain bar is smaller than the deform bar.

Keywords:
Bond stress; slip; tension test; failure pattern; lap splice.