Tsai, Ren-JieRen-JieTsaiHenry, Richard S.Richard S.HenryElwood, Kennth J.Kennth J.ElwoodSHYH-JIANN HWANGCheng, Min-YuanMin-YuanCheng2026-04-142026-04-142026-02-1501410296https://www.scopus.com/record/display.uri?eid=2-s2.0-105030245372&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/737183A dataset comprising experimental results from 45 diagonally reinforced concrete (RC) coupling beams, including 21 specimens tested with some form of axial restraint conditions, were analyzed to investigate the influence of axial restraint on the seismic response of diagonally RC coupling beams. Statistical analysis revealed that the provided axial restraint significantly affected the coupling beam maximum strength, with enhanced strengths of up to three times the nominal design strength. The measured strengths were found to align closely with the flexural strength calculated based on the probable moment strength at the beam ends. In addition, a simple strength estimation method that incorporates the axial restraint effect was proposed, which provided a reasonable approximation of the experimental responses. The analyses indicated that the initial stiffness was slightly increased due to axial restraint conditions, with stiffness showing a strong correlation to the beam aspect ratio. However, the influence of axial restraint conditions on the chord rotation capacity of coupling beams was less pronounced. Furthermore, a proposed strength design procedure indicated that the diagonal reinforcement in coupling beams can be reduced by approximately 20 % compared to those determined by existing design provisions.trueAxial restraintCoupling beamsDiagonally reinforcedExperimental datasetReinforced concreteStrength designStrength estimationjournal article10.1016/j.engstruct.2025.1217592-s2.0-105030245372