ECC-FRP格栅复合材料修复滨海锈蚀混凝土梁的受剪性能和耐久性研究

Corrosion of steel stirrup in marine environment causes decreasing shear capacity of reinforced concrete (RC) beam and secondary corrosion after the structural retrofitting. This project proposes a new method to strengthen existing deteriorated RC beam, replacing the concrete cover around steel stirrup with engineered cementitious concrete (ECC) and embedding FRP grid in ECC to form ECC-FRP composite. The embedment of FRP grid ensures good utilization of its tensile capacity and increases the shear capacity of the strengthened RC beam. ECC is superior in resisting chloride permeability, which prevents chloride penetration from marine environment to steel stirrup and the resultant corrosion. Moreover, ECC forms distributed tiny cracks when subjected to external loading, and the distributed tiny cracks, instead of several critical large cracks, solve the problem of intermediate crack-induced debonding (IC-debonding). The high tensile capacity of ECC can also improve the bond performance between ECC and FRP grid..This project aims to: (1) investigate the shear performance and sustainability of deteriorated RC beam strengthened with ECC-FRP mesh, including material property, bond performance and structural performance under shear loading; (2) discover the composite action between ECC-FRP grid, concrete and steel stirrup; and (3) finally propose a design method for ECC-FRP grid composite strengthening system.

针对滨海环境中箍筋锈蚀导致的混凝土梁抗剪承载力不足和加固后结构性能反复退化（即二次锈蚀）问题，本项目提出一种新型加固方法，即用水泥基复合材料（ECC）置换箍筋周围富含腐蚀介质的混凝土保护层，并将FRP格栅嵌固在ECC材料中，形成ECC-FRP格栅复合材料，二者协同变形，共同工作。FRP格栅材料嵌固在ECC中，有效抑制界面剥离，提高结构抗剪承载力。ECC内部置换富含腐蚀介质的混凝土，并阻断外部环境中腐蚀介质向箍筋的迁移，彻底解决二次锈蚀问题；高受拉强度保障FRP格栅对抗剪承载力的提升效果。本项目拟从材性、粘结特性、受剪特性和抗二次锈蚀四方面，系统地研究ECC-FRP格栅复合材料的本构关系、复合材料-混凝土界面的粘结特性、修复锈蚀钢筋混凝土梁的受剪性能和耐久性，确定最优加固方案，揭示复合材料、混凝土和箍筋协调变形工作原理，建立ECC-FRP格栅抗剪修复锈蚀混凝土梁的设计方法。

针对滨海环境中箍筋锈蚀导致的混凝土梁抗剪承载力不足和加固后结构性能反复退化(即二次锈蚀)问题，本项目提出了一种新型加固方法，即用水泥基复合材料(ECC)置换箍筋周围富含腐蚀介质的混凝土保护层，并将FRP格栅嵌固在ECC材料中，形成ECC-FRP格栅复合材料，二者协同变形，共同工作。FRP格栅材料嵌固在ECC中，有效抑制界面剥离，提高结构抗剪承载力。ECC内部置换富含腐蚀介质的混凝土，并阻断外部环境中腐蚀介质向箍筋的迁移，彻底解决二次锈蚀问题;高受拉强度保障FRP格栅对抗剪承载力的提升效果。本项目从材性、粘结特性、受剪特性和抗二次锈蚀四方面，系统地研究了ECC-FRP格栅复合材料的本构关系、复合材料-混凝土界面的粘结特性、修复锈蚀钢筋混凝土梁的受剪性能和耐久性，确定了最优加固方案 ，揭示了复合材料、混凝土和箍筋协调变形工作原理，建立ECC-FRP格栅抗剪修复锈蚀混凝土梁的设计方法。