Title:
Proposal for Bond Strength Considering Bond Characteristics of Beam Flexural Rebar on Interior Beam-Column Joints. Part I: Focusing on Concrete Compressive Strength
Author(s):
Min-Su Jo, Hyeong-Gook Kim, Dong-Hwan Kim, Su-A Lim, Yun-Soo Choi, Jung-Yoon Lee, Kil-Hee Kim
Publication:
IJCSM
Volume:
20
Issue:
Appears on pages(s):
Keywords:
RC interior beam-column joint, Penetrated beam rebar, Concrete compressive strength, Bond characteristics, Bond strength
DOI:
10.1186/s40069-025-00813-0
Date:
1/31/2026
Abstract:
The bond characteristic of beam longitudinal rebar penetrating reinforced concrete beam-column interior joints under cyclic loading is influenced by various factors such as compressive strength of concrete, yield strength of main rebar, diameter, and axial load ratio of column. In this study, the bond characteristics of beam longitudinal rebar were investigated through an experimental method that directly simulates the internal stress state of the joint; a bond strength equation reflecting the bond behavior focused on the concrete compressive strength was proposed. The experiments were conducted by fabricating eight specimens with concrete compressive strength as the main variable and performing cyclic loading tests. Through the experimental results, it was confirmed that the mechanism of bond failure of beam longitudinal rebar penetrating into the joint is one in which bond stress in the tensile region results in degradation of the joint core region; the burden of bond stress increases due to transfer to the compression region; finally, bond failure of the joint core region occurs due to degradation of bond stress in the compression region. Based on the experimental results, the proposed bond strength equation, which reflects the bond characteristics of longitudinal reinforcement at the internal joint, is proportional to the 3/4 power of the concrete compressive strength, and shows a prediction result that is about 5–16% better than that of the existing design equation. In addition, in order to propose the required column depth, it is necessary to consider various parameters such as the column axial force ratio, yield strength of beam longitudinal rebar, and diameter.