Experimental Study on Restraining Headed Bars in Roof- Exterior Connection

• Published in: ACI structural journal Vol. 118; no. 6; pp. 251 - 265
• Main Authors: Baek, Jang-Woon, Kang, Thomas H.-K
• Format: Journal Article
• Language: English
• Published: Farmington Hills American Concrete Institute 01.11.2021
• Subjects: Analysis; Bars; Bars (Engineering); Beam-columns; Concrete; Concrete properties; Constraining; Cyclic loads; Design; Design techniques; Evaluation; Mechanical properties; Reinforced concrete; Roofs; Strength of materials; Testing; Yield stress; South Korea; United States > US
• ISSN: 0889-3241; 0889-3241; 1944-7361
• DOI: 10.14359/51732851

For roof-level exterior beam-column connections, the design requirement associated with side-face blow out failure for restraining 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. Keywords: concrete capacity design; concrete side-face blowout failure; headed bar; head-restraining bar; knee joint; prying action; roof-level exterior beam-column connection.