Experimental study on restraining headed bars in roof-exterior connection

For roof-level exterior beam-column connections, the design requirementassociatedwithside-faceblowoutfailureforrestraining headed bars can be alleviated by considering the concrete contribution. To evaluate concrete strength, investigation of the safety against side-face blowout failure of such knee-joint connections is deemed warranted. In this study, existing experimental tests for roof-exterior beam-column connections were reviewed and a cyclic loading test for a full-scale roof-exterior connection specimen was performed to examine concrete side-face blowout strength. In addition, the head-restraining bar area required in the current ACI 318 design provision and in the original ACI 349-97 design provision was evaluated. Results indicate that the head-restraining bar area required in ACI 349-97 was sufficient to prevent concrete side-face blowout failure for both Type 1 and 2 specimens. For conservative design, an explicit equation was also proposed for design of head-restraining bars in roof-level exterior connections.