Numerical Investigation of Reinforced Concrete Deep Beams with Square Web Openings: Influence of Opening Configuration and Reinforcement Detailing

Document Type : Original Article

Authors

1 Institute of Advanced Technology, Faculty of Engineering, Arak University, Arak, Iran

2 Faculty of Earth Sciences Engineering, Arak University of Technology, Arak, Iran

Abstract

Web openings are frequently introduced into reinforced concrete deep beams to accommodate utility services; however, these discontinuities may significantly disrupt the internal load-transfer mechanism and adversely affect structural performance. This study investigates the influence of square opening size and location on the behavior of reinforced concrete deep beams using nonlinear finite element analysis in ABAQUS. Unlike previous studies that primarily focused on individual parameters such as opening geometry, opening location, or strengthening techniques, the present study systematically investigates the combined effects of square opening size, vertical opening location, and reinforcement detailing on the structural behavior of reinforced concrete deep beams. The numerical model was developed based on the concrete damaged plasticity (CDP) approach and validated against previously published experimental results, showing good agreement in terms of load-displacement response, crack patterns, and ultimate load capacity. Six deep beam specimens containing square web openings with side lengths of 200 and 250 mm positioned at various levels within the shear span were analyzed. The effects of opening configuration on crack propagation, principal stress distribution, and load-carrying capacity were evaluated. The results showed that openings located at the mid-depth of the web produced the greatest disturbance to the main compression strut, leading to increased stress concentration, extensive diagonal cracking, and reduced structural capacity. Increasing the opening size further intensified these effects by disrupting a larger portion of the principal compression strut. To mitigate these adverse effects, a modified reinforcement arrangement was proposed by redistributing web reinforcement around the opening and adding confinement reinforcement in critical regions. This detailing increased the ultimate load capacity by approximately 3-10%, delayed crack initiation by up to 44%, and improved principal stress redistribution. Overall, the proposed reinforcement arrangement effectively enhanced the structural behavior of deep beams with square web openings and provides practical guidance for reinforcement design in disturbed regions.

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Main Subjects

References

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History

  • Receive Date: 02 July 2026
  • Revise Date: 23 July 2026
  • Accept Date: 04 September 2026
  • First Publish Date: 04 September 2026

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