| Title |
Failure Modes and Strengths of Headed Bars Anchored in Exterior Beam-Column Joints |
| Authors |
Chun Sung-Chul ; Lee Sung-Ho |
| Keywords |
Headed Bar ; Exterior Beam-column Joint ; Anchorage ; Cover ; Bar Spacing |
| Abstract |
New provisions of ACI 318-08 specify the development details of headed bars. The provisions result in the development length (ldt) of approximately 80% of the length of hooked bars (ldh) with restrictions on material strengths, cover thickness, and spacing between bars. Due to quite limited experimental researches used in developing the provisions, the anchorage strengths of headed bars are dependent on applied members even though they have same development length. The development length determined by ACI 318-08 can yield an unsafe result in beam-column joints. In addition, it requires more than 4db for clear bar spacing. This can be a significant restriction, as the exterior beam-column joint mostly involves the use of headed bars to reduce steel congestion. It is impossible to design 4db of clear spacing between layers of beam longitudinal bars. To develop a reasonable and safe design of headed bars in beam-column joint, failure modes of headed bars and models for anchorage capacities were proposed by modifying similar models. Experimental study was also conducted to verifying the proposed models. Moreover, available test data for beam-column joints with headed bars were compared with the models. Finally, design guidelines on headed bars anchored in beam-column joints were suggested. |