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<p>The main contribution of this study lies in advancing the understanding and application of external prestressing as a retrofitting technique for deteriorated or underperforming concrete structures. Specifically, this work offers; comprehensive experimental investigations demonstrating the effectiveness of the external prestressing technique under static loading. The results highlight improvements in structural performance, including increased load capacity, delayed crack initiation, and enhanced energy dissipation. This study experimentally investigates the structural behavior of normal strength concrete beams strengthened with externally prestressed strands. A total of five specimens were prepared and tested under four-point bending to assess load-deflection performance, crack formation, and failure modes, each having dimensions of 1700&#xa0;mm in length, 400&#xa0;mm in height, and 180&#xa0;mm in width. The novelty of this study lies in the combined investigation of prestressing level and deviator configuration on externally prestressed beams, a topic not thoroughly addressed in previous literature. Three variables were investigated in this study: number of deviators, different levels of external prestressing force, and an eccentricity of the strands. Two deviator configurations were used: a single deviator located at the mid-span of the beam, and two deviators placed at one-third points along the beam span. Two levels of external prestressing force were applied: 65% and 85% of the ultimate tensile strength of the strands. The prestressing steel prestressing cables were placed either 200&#xa0;mm below the beam’s neutral axis (i.e., at the bottom surface of the beam) or at mid-height (zero eccentricity). Test results indicated that the prestressed normal strength concrete beams exhibited an improvement in ultimate load-carrying capacity of approximately 58.8%. With regard to cracking, the first cracking load increased by about 302.5%. The results also showed that the beams with the highest prestressing force demonstrated the best overall structural performance, suggesting practical applicability. Reducing the eccentricity of the strands to zero led to an increase in the ultimate load-carrying capacity of approximately 49.7%, while the specimen with 200&#xa0;mm eccentricity achieved a 56.6% improvement in ultimate load capacity. These results provide practical insights for engineers and designers aiming to retrofit or strengthen existing concrete structures using external prestressing techniques.</p>

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Strengthening of reinforced concrete beams using external prestressed technique under the effect of static loads

  • 期刊论文

  • 发表日期：

    2025年10月18日

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  • Aamer Najim Abbas,
  • Mohammed J. Hamood,
  • Wael Shawky Abdulsahib

摘要

The main contribution of this study lies in advancing the understanding and application of external prestressing as a retrofitting technique for deteriorated or underperforming concrete structures. Specifically, this work offers; comprehensive experimental investigations demonstrating the effectiveness of the external prestressing technique under static loading. The results highlight improvements in structural performance, including increased load capacity, delayed crack initiation, and enhanced energy dissipation. This study experimentally investigates the structural behavior of normal strength concrete beams strengthened with externally prestressed strands. A total of five specimens were prepared and tested under four-point bending to assess load-deflection performance, crack formation, and failure modes, each having dimensions of 1700 mm in length, 400 mm in height, and 180 mm in width. The novelty of this study lies in the combined investigation of prestressing level and deviator configuration on externally prestressed beams, a topic not thoroughly addressed in previous literature. Three variables were investigated in this study: number of deviators, different levels of external prestressing force, and an eccentricity of the strands. Two deviator configurations were used: a single deviator located at the mid-span of the beam, and two deviators placed at one-third points along the beam span. Two levels of external prestressing force were applied: 65% and 85% of the ultimate tensile strength of the strands. The prestressing steel prestressing cables were placed either 200 mm below the beam’s neutral axis (i.e., at the bottom surface of the beam) or at mid-height (zero eccentricity). Test results indicated that the prestressed normal strength concrete beams exhibited an improvement in ultimate load-carrying capacity of approximately 58.8%. With regard to cracking, the first cracking load increased by about 302.5%. The results also showed that the beams with the highest prestressing force demonstrated the best overall structural performance, suggesting practical applicability. Reducing the eccentricity of the strands to zero led to an increase in the ultimate load-carrying capacity of approximately 49.7%, while the specimen with 200 mm eccentricity achieved a 56.6% improvement in ultimate load capacity. These results provide practical insights for engineers and designers aiming to retrofit or strengthen existing concrete structures using external prestressing techniques.