增大截面二次加固梁的正截面抗弯性能试验研究

为评估增大截面二次加固对钢筋混凝土梁正截面抗弯性能的提升效果,文章对未加固梁、粘钢首次加固梁以及增大截面二次加固梁进行系统的试验研究。通过荷载-挠度曲线、钢筋和混凝土的荷载-应变曲线、裂缝分布及破坏形态等数据,深入分析各类加固方式对梁承载力及变形性能的影响。结果表明:增大截面二次加固可显著提高梁的抗弯承载力和刚度,极限荷载比未加固梁提高了112%,且相比粘钢加固梁提高了49%;二次加固梁有效降低了原梁纵向钢筋的应力水平,原受拉钢筋的应变较未加固梁下降约75%;二次加固梁的混凝土截面应变沿高度呈线性分布,验证了平截面假定的适用性。基于试验结果,推导出增大截面二次加固梁的承载力计算公式,且公式计算值与试验结果吻合较好,为工程应用提供了可靠的设计依据。

To explore the improvement level of the flexural behavior of the normal section of the reinforced concrete beam strengthened by secondary reinforcement with section enlargement, experimental studies were conducted on unstrengthened beams, beams strengthened with bonded steel plates for the first time, and beams subjected to secondary strengthening by section enlargement. The effects of various strengthening methods on the bearing capacity and deformation performance of the beams were evaluated by analyzing the load-deflection curve, load-strain curve of steel bar and concrete, crack distribution and failure mode. The results show that the secondary strengthening by section enlargement can effectively enhance the flexural capacity and flexural stiffness of the beams. The ultimate load of the beams with secondary section enlargement increases by 112% compared to the unstrengthened beams, and by 49% compared to the steel-bonded strengthened beams. Additionally, this method effectively reduces the stress level in the longitudinal reinforcement of the original beams, with the strain in the original tensile reinforcement decreasing by 75% compared to the unstrengthened beams. The strain distribution across the normal section of the concrete in the beams subjected to secondary strengthening approximately follows a linear pattern, which is consistent with the plane section assumption. Finally, the bearing capacity formula of the beams strengthened by secondary reinforcement with enlarged section was deduced, and the calculated values from the bearing capacity formula show good agreement with the experimental results. This study offers reliable design references for engineering applications.