考虑多重尺寸效应的FRP抗剪加固混凝土梁的可靠度分析及设计

Size effect is a common issue in civil engineering. FRP shear strengthened reinforced concrete (RC) structures show an obvious size effect on the level of material, structural component and design method. However, these size effects have not been considered comprehensively in the existing reliability-based design for FRP shear strengthening, which pose a deviation of safety and economy for reinforced structures. Thus, aiming to improve the balance between reliability and economy for the design method, the study of reliability-based design for FRP shear strengthened RC beams considering multiple size effects is carried out in this project. On the level of material, the effect of FRP material size on mechanical properties and uncertainties are further identified through experimental analysis. On the level of structural component, the effect of beam size on FRP shear contribution model, reliability analysis and design parameter are performed based on a comprehensive test database of FRP shear strengthened RC beams. On the level of design method, the effect of reliability size on the designable area and economic efficiency for FRP shear strengthening is performed with the concept of FRP shear contribution ratio. Besides, the importance sampling method is utilized to evaluate reliability index with high efficiency and accuracy. This research will be a useful supplement for the reliability-based design of FRP shear strengthening, and of a great significance to ensure the safety and economy for reinforced structures.

尺寸效应是土木工程领域普遍存在的现象，FRP抗剪加固混凝土结构在材料、构件及设计方法层次存在明显的尺寸效应。现有FRP抗剪加固可靠度设计尚未全面考虑上述尺寸效应，严重影响加固结构的安全性及经济性。为此本项目拟开展考虑多重尺寸效应的FRP抗剪加固混凝土梁的可靠度分析及设计方法的系统研究，旨在提升抗剪加固设计方法的可靠性，平衡加固结构的安全性与经济性。在材料层次，通过试验量化FRP材料尺寸效应对FRP力学性能不确定性的影响；在构件层次，基于FRP抗剪加固试验数据库，分析构件尺寸效应对FRP抗剪贡献模型评估及可靠度设计的影响；在设计方法层次，结合FRP抗剪贡献比例，分析“可靠度尺寸效应”对FRP加固有效性及经济效益的影响；同时，采用重要抽样方法计算可靠度，提高计算精度和效率。研究成果是对FRP抗剪加固可靠度设计理论的有益补充，对提升加固结构的服役安全性、确保经济性有重要指导意义。

尺寸效应是土木工程领域普遍存在的现象，FRP抗剪加固混凝土结构在材料、构件及设计方法层次存在明显的尺寸效应。本项目针对FRP抗剪加固混凝土梁，基于数值分析方法，研究不同理论模型、设计方法、设计规范下的可靠度水平；校核不同条件下的FRP设计参数，为FRP抗剪加固提供合理指导；探讨相应的设计经济性，揭示尺寸效应对FRP抗剪加固的可靠度分析及设计的影响，进一步平衡加固结构的安全性与经济性。本项目主要创新成果包含以下方面：.（1）构建了较为完善的FRP抗剪加固混凝土梁试验数据库，建立了FRP力学性能及其不确定性模型，为FRP抗剪加固可靠度分析及设计提供基础。.（2）基于试验数据库，量化分析了包含不同构件尺寸的FRP抗剪加固混凝土梁的可靠度，评估了不同理论模型、不同设计规范的设计可靠度水平，提出了FRP设计参数建议值。.（3）提出了“可靠度尺寸效应”，明确了不同设计规范的FRP抗剪加固的经济性及可设计区域，揭示了由设计方法引起的尺寸效应对FRP抗剪加固设计的影响。