本文提出了一种新型C型UHPC-砖砌体组合托换梁截面形式及其托换改造方法。通过有限元模拟, 系统研究了7根UHPC-砌体组合梁及3根普通混凝土 (NC) -砌体组合梁的受弯性能, 重点分析了配筋率、UHPC层厚度和强度等参数的影响。结果表明: 提高UHPC层厚度、增大纵筋配筋率提高托换梁的屈服荷载与峰值荷载。当配筋率从1. 16%提高到1. 81%与2. 28%时, 屈服荷载增加了15. 9%和82. 53%, 峰值荷载提高了49. 3%与86. 6%。当UHPC层厚度从30mm增至90mm时, 开裂荷载提升了29%。与普通混凝土组合梁相比, UHPC组合梁在承载力方面具有明显优势。基于平截面假定, 建立了该类组合梁的正截面受弯承载力计算公式。计算结果与有限元模拟结果高度吻合, 证明了所提理论公式的正确性与可靠性。研究结果可为后续的工程应用提供理论基础。

This paper proposes a novel C-shaped UHPC-brick masonry composite underpinning beam section form. and its underpinning transformation method. The flexural performance of seven UHPC-masonry composite beams and three normal concrete-masonry composite beams were systematically studied by finite element simulation, with a focus on the effects of parameters such as reinforcement ratio, UHPC layer thickness and UHPC strength. The results showed that increasing the longitudinal reinforcement ratio and the thickness of UHPC layer can improve the yield load and peak load of the beam. When the reinforcement ratio increased from 1. 16 % to 1. 81 % and 2. 28 %, the yield load increased by 15. 9 % and 82. 53 %, respectively, and the peak load increased by 49. 3 % and 86. 6 %. When the thickness of UHPC layer was increased from 30mm to 90mm, the cracking load increased by 29 %. Compared with ordinary concrete composite beams, UHPC composite beams have a significant advantage in bearing capacity. Based on the assumption of plane section, the calculation formula of flexural capacity of this kind of composite beam was established. The calculation results were in good agreement with the finite element simulation results, which proves the correctness and reliability of the proposed theoretical formula. The research results can provide a theoretical basis for subsequent engineering applications.