Effect of Infill Wall Opening Ratio on the Mechanical Characteristics of Reinforced Concrete Frames

Masonry Infill Walls Reinforced Concrete Frames Stiffness Structural Behavior Effects of Wall Openings

Authors

  • Phu-Anh-Huy Pham
    phampanhhuy@duytan.edu.vn
    1) Institute of Research and Development, Duy Tan University, Da Nang, 550000, Vietnam. 2) Faculty of Civil Engineering, Duy Tan University, Da Nang, 550000, Viet Nam https://orcid.org/0000-0002-9476-0910
  • Cao-Vinh Le 1) Institute of Research and Development, Duy Tan University, Da Nang, 550000, Vietnam. 2) Faculty of Civil Engineering, Duy Tan University, Da Nang, 550000, Viet Nam
  • Van-Tien Nguyen 2) Faculty of Civil Engineering, Duy Tan University, Da Nang, 550000, Vietnam. 3) Huu Tien Limited Construction Company, 55000, Danang, Viet Nam

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This study investigated the influence of infill wall (IW) opening ratios on the mechanical performance of reinforced concrete (RC) frames using a novel numerical model. The proposed model incorporated stiffness degradation and a nonlinear "Gap Element" to simulate the interaction between RC frames and IWs under seismic loading. A 3D finite element model was developed in SAP2000 and calibrated using validated experimental data. Parameters such as IW thickness, opening ratio (0–100%), and opening position (symmetric, asymmetric, corner) were systematically varied to assess their effects on lateral displacement , fundamental period , shear force , and bending moment . The results indicated that increasing the opening ratio significantly reduces frame stiffness, especially beyond 40%, and leads to substantial increases in displacement. Corner openings were found to have the most detrimental impact, while thicker walls (≥220mm) can partially mitigate stiffness loss. However, at ratios above 60%, even thick IWs failed to preserve structural performance. Based on these findings, a limit of 40% opening ratio was recommended for design purposes, and reinforcement was advised for higher ratios. The study provides a practical framework for optimizing the seismic and structural design of RC frames with openings in IWs, contributing new thresholds and modeling strategies for improved performance.