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.