疲劳荷载下FRP筋钢纤维高强混凝土梁的破坏机理与计算理论

Fiber reinforced polymer（FRP）as well as fiber reinforced high-strength concrete are two types of high performance materials. Aimed at the key problems that the steel corrosion and concrete cracking too soon exhibited in concrete beams reinforced with steel bars and the excessive cracking-width, deformation and the significant stiffness degradation expressed in concrete beams reinforced with FRP rebas, the bonding-behavior between the FRP bars and steel fiber reinforced high-strength concrete and the flexural behavior of steel fiber reinforced high-strength concrete beams reinforced with FRP bars when subjected to fatigue loading will be investigated in this project. Based on the systematic test research, combining with mathematical statistics method, fatigue damage cumulative theory and nonlinear FEM, the fatigue failure mechanism on the bonding behavior of FRP rebars-steel fiber reinforced high-strength concrete and flexural behavior of FRP rebars reinforced steel fiber reinforced high-strength concrete beams will be studied. And then, the bond-slip constitutive model of FRP bars to steel fiber reinforced high-strength concrete, the stiffness degradation model and Fatigue strength prediction model of steel fiber reinforced high-strength concrete beams reinforced with FRP bars will be established, and the calculating thoeries, numerical simulation method and the construction measures such as balanced depth of steel reinforced high-strength concrete layer in tensile zone for the steel fiber reinforced high-strength concrete beams reinforced with FRP bars will be put forward. The expected research results will exhibit the great significance on developing design theory of FRP reinforced concrete structure & fiber reinforced concrete structure and promoting the engineering application of FRP bars & steel fiber reinforced high-strength concrete in the related projects.

针对钢筋混凝土梁的钢筋锈蚀、易开裂和FRP筋混凝土梁的裂缝过宽、刚度退化和变形过大等问题，本项目通过疲劳荷载下FRP筋钢纤维高强混凝土粘结试验和FRP筋钢纤维高强混凝土梁的受弯疲劳试验，结合数理统计、疲劳损伤理论和非线性有限元分析方法，研究FRP筋钢纤维高强混凝土的界面疲劳粘结损伤与失效机理和FRP筋钢纤维高强混凝土梁受弯疲劳损伤演化过程与破坏机理，建立FRP筋钢纤维高强混凝土粘结退化模型与粘结滑移本构模型和FRP筋钢纤维高强混凝土梁的损伤演化、刚度、裂缝宽度、疲劳强度与受弯承载力计算模型，提出达到FRP筋全截面钢纤维高强混凝土梁受弯疲劳性能的界限受拉区钢纤维高强混凝土层厚等构造要求，形成疲劳荷载下FRP筋钢纤维高强混凝土梁的计算理论体系。预期成果对丰富和发展FRP筋混凝土结构和钢纤维混凝土结构设计理论，推动FRP筋和钢纤维高强混凝土的工程应用具有重要的理论意义和实用价值。

本项目进行了重复荷载作用下FRP筋与混凝土粘结性能、FRP筋钢纤维高强混凝土梁受弯性能、海水侵蚀预开裂BFRP筋钢纤维混凝土梁受弯性能试验和疲劳荷载作用下BFRP筋钢纤维高强混凝土梁的受弯性能试验。分析了BFRP筋直径与肋痕深度、混凝土强度等级、钢纤维掺量等对BFRP筋混凝土荷载-滑移关系曲线以及粘结破坏形态的影响，研究了BFRP筋混凝土粘结疲劳性能的损伤与失效机理，提出了BFRP筋-混凝土粘结疲劳损伤模型及FRP筋界面粘结摩擦修正系数；分析了FRP筋配筋率、钢纤维类型及其掺量、混凝土强度等级、荷载特征参数、环境因素等因素对BFRP筋钢纤维高强混凝土梁和预开裂BFRP筋钢纤维高强混凝土梁的裂缝开展、混凝土极限应变、荷载挠度曲线、骨架曲线、刚度退化、残余变形及延性的影响，研究了重复及疲劳荷载作用下BFRP筋钢纤维高强混凝土梁的损伤演化规律与受弯破坏机理；基于数理统计方法和结构设计原理，综合考虑BFRP筋及其与钢纤维高强混凝土粘结性能特点，建立了重复及疲劳荷载作用下BFRP筋钢纤维高强混凝土梁的受力模型与疲劳强度方程，提出了重复及疲劳荷载作用下BFRP筋钢纤维高强混凝土梁受弯性能计算方法。