This study is performed to examine the effectiveness of using externally prestressed strands for shear strengthening of reinforced concrete (RC) deep beams with large openings. A total of nine RC deep beams with large openings having a rectangular cross-section of 150 × 400 mm and a total length of 1600 mm were constructed and tested up to failure under three-point bending. The studied parameters were the opening ratio and the strengthening scheme using prestressed strands. These beams were divided into three groups depending on strengthening scheme, Group I (unstrengthening), Group II (strengthened by horizontal external strands) and Group III (strengthened by vertical external strands). For each group, three opening ratios were adopted (0.4, 0.6 and 0.8). Two large rectangular openings, one in each shear span were placed symmetrically about the centerline of the beam. Externally horizontal prestressed strands scheme was found very effective in upgrading the shear strength of RC deep beams. The ultimate strength gain caused by the horizontal scheme of strengthening was in the range of 32–53%. Also, this scheme of strengthening resulted in a remarkable decrease in tension reinforcement strain for all opening ratios. The reduction in tension reinforcement strain was in the range of 60–91%. While, the vertical scheme of strengthening had an insignificant effect on tension reinforcement strain. On the contrary, this scheme of strengthening showed a notable decrease in stirrups strain in the range of 142 – 158 %. Analytical solution using the strut and tie model (STM) has been modified to adjust the schemes of strengthening strands. The predicted shear strengths of RC deep beams with openings with and without strengthening were verified with the experimental results with a convergence of 0.93 on average.

进行这项研究是为了检验使用外部预应力绞线进行大开口钢筋混凝土（RC）深梁抗剪加固的有效性。总共构造了九个具有大开口的RC深梁，矩形截面为150×400 mm，总长度为1600 mm，并进行了三点弯曲试验直至破坏。研究的参数是开孔率和使用预应力钢绞线的加固方案。根据加固方案，这些梁分为三组：第一组（未加固），第二组（由水平外层加固）和第三组（由垂直外层加固）。对于每组，采用三个开口率（0.4、0.6和0.8）。两个大的矩形开口 每个剪切跨度中的一个相对于梁的中心线对称放置。外部水平预应力钢绞线方案对提高RC深梁的抗剪强度非常有效。水平加固方案导致的最终强度增加在32％至53％之间。而且，这种加强方案导致所有开口率下的张力加强应变显着降低。张力增强应变的降低幅度为60-91％。同时，垂直加固方案对拉伸加固应变的影响不大。相反，这种加强方案表明箍筋应变显着降低了142 – 158％。修改了使用支撑和系紧模型（STM）的分析解决方案，以调整加固线的方案。