| Title |
An Experimental Study on the Lap Strength of Headed Steel Reinforcements with Lap-spliced |
| Authors |
Lee Yong-Taeg ; Kim Seung-Hun ; Chea Seo-Ho ; Bahn Byong-Youl |
| Keywords |
Headed Bars ; Lap Length ; Lap Splice ; Bond Stress ; Bearing Stress |
| Abstract |
Headed bars have used to the anchoring of the tension or compression longitudinal bars and of the shear reinforcing bars. Recently, lap splices of headed steel reinforcements have been attempted to the joints of precast concrete members and to the connections between old and new concrete members. Previous experimental and analytical researches for the lap splice of headed bars hadn't be studied except Michael's 2003. In this research, the experimental works were conducted to study the lap strength of the headed reinforcements placed in a horizontal single layer. Ten lap splice specimens were tested. Wide beam specimens were fabricated with a lap splice at mid-span. They were loaded in flexure, placing the lap splice in tension. The variables in this study were: lap length(6∼16 times the diameter of reinforcement), diameter of reinforcement(D19, D25), and debonded versus bonded bars. Specimens were instrumented to measure the load on the specimen, strain along the reinforcements with in the lap zone, and mid-span deflection. The cracking behavior was also observed and recorded. The following conclusions were drawn from the test results in this study; 1) The initial crack of the specimens lapped developed at the heads of reinforcements. The specimens failed by the crack with the struts acting between the opposing heads of lapped reinforcements. 2) Bond contribution to increase strength and deformation was great. In accordance with the this result, it is necessary to consider the bond strength for the lap length design of headed reinforcements. 3) CCD method evaluated the maximum strength as 2.21∼4.96 times the test maximum strength. It was caused by the reduction of lap length where headed reinforcements were located less than 1.5 times lap length from three or more edges. For design guideline of the lap strength of headed reinforcements, it needs to consider the bearing stress of heads and the bond stress of reinforcements. |