Title:
Side-Face Blowout Strength of Two-Layer Headed Bars Embedded in Exterior Beam-Column Joints
Author(s):
Hye-Jung Sim and Sung-Chul Chun
Publication:
Structural Journal
Volume:
119
Issue:
2
Appears on pages(s):
221-231
Keywords:
exterior beam-column joint; headed bar; side-face blowout failure; two layers
DOI:
10.14359/51734338
Date:
3/1/2022
Abstract:
The side-face blowout area of two-layer headed bars in an exterior beam-column joint could be overlapped by each headed bar and, therefore, the anchorage strength of the individual headed bar could be reduced. However, ACI 318-19 and previous studies did not consider the effects of layer-to-layer spacing. To evaluate the anchorage strength of two-layer headed bars in the exterior beam-column joint, a simulated exterior beam-column joint test was conducted with 43 mm (No. 14) headed bars of 550 MPa (80 ksi) of design yield strength. The effects of layer-to-layer spacing, embedment length, and side cover on the anchorage strength of two-layer headed bars were experimentally estimated. Degradations of the anchorage strength due to overlapping failure area are very similar to the degradation of the side-face blowout strength of the group anchor subjected to tension, and the side-face blowout strength of two-layer headed bars can be predicted by using a spacing factor. A design equation for the development length of two-layer headed bars is proposed by applying the spacing factor developed in this study into a design equation for the single-headed bar developed from a previous study.
Related References:
1. Shao, Y.; Darwin, D.; O’Reilly, M.; Lequesne, R. D.; Ghimire, K.; and Hano, M., “Anchorage of Conventional and High-Strength Headed Reinforcing Bars,” SM Report No. 117, University of Kansas Center for Research, Lawrence, KS, 2016, 234 pp.
2. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
3. Chun, S.-C.; Choi, C.-S.; and Jung, H.-S., “Side-Face Blowout Failure of Large-Diameter High-Strength Headed Bars in Beam-Column Joints,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb. 2017, pp. 161-172. doi: 10.14359/51689161
4. Marques, J. L. G., and Jirsa, J. O., “A Study of Hooked Bar Anchorages in Beam-Column Joints,” ACI Journal Proceedings, V. 72, No. 5, May 1975, pp. 198-209.
5. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 519 pp.
6. Furche, J., and Eligehausen, R., “Lateral Blow-Out Failure of Headed Studs Near a Free Edge,” Anchors in Concrete-Design and Behavior, SP-130, American Concrete Institute, Farmington Hills, 1991, pp. 235-252.
7. Joint ACI-ASCE Committee 352, “Recommendations for Design of Beam-Column Connections in Monolithic Reinforced Concrete Structures (ACI 352-02) (Reapproved 2010),” American Concrete Institute, Farmington Hills, MI, 2002, 38 pp.
8. Thompson, M. K.; Jirsa, J. O.; and Breen, J. E., “Behavior and Capacity of Headed Reinforcement,” ACI Structural Journal, V. 103, No. 4, July-Aug. 2006, pp. 522-530.
9. Chun, S.-C., “Components of Side-Face Blowout Strengths of Headed Bars in Exterior Beam-Column Joints,” ACI Structural Journal, V. 116, No. 2, Mar. 2019, pp. 159-169. doi: 10.14359/51711141
10. Natrella, M. G., Experimental Statistics—National Bureau of Standards Handbook 91, 1996, pp. 1-14.