BOND CHARACTERISTICS AND ROTATIONAL CAPCITY FOR REINFORCED CONCERETE EXTERIOR JOINTS AS AFFECTED BY BONDED PART AND RIB GEOMETRY FOR STEEL REINFORCEMENT BARS

Abstract

The need of high quality of concrete is increased in the recent years. Using steel of high grade and maximize the benefit of using this steel became necessary. So, different ribs are used for steel bars to increase the bond strength between steel reinforcement and concrete. There are different forms of rib geometry of I he deformed bars with either Crescent or Tree profiles for all types of steel in the Egyptian market. Anchorage of reinforcing bars of the beam-column connections is an important design consideration for providing continuity and safety m reinforced concrete structures. This anchorage may be provided by development of straight bars into the exterior joints, The Egyptian Codes of practice 208 (1995) [1] and 203 (2001) [2] give the values of development length of the deformed reinforcement bars regardless the geometry and the relative area of the ribs. The main objectives of this research is to study the effect of the rib geometry and the relative rib area on the bond characteristics, the rotational capacity, crack pattern, the mode of failure, the deformation capacity and bond stress of the exterior joints of the structure. Six specimens of cantilever-to-column connections, which represent exterior joints in structural system, were tested. Type of steel, rib geometry, and bonded part were variables in the tested specimens. The study concluded that the geometry of the ribs and the bonded part in addition to the steel type have reasonable effect on the bond characteristics of the cantilever-to-column joints and hence on the ultimate load capacity of the joint