CFRP-混凝土界面粘结的疲劳性能试验研究

Experimental Study of CFRP-concrete Interfacial Bonding Fatigue Behavior

外贴FRP是重要的混凝土结构加固技术,但目前对外贴FRP加固混凝土结构的疲劳性能研究尚不充分,尤其对FRP-混凝土粘结界面的疲劳退化规律和破坏模式的研究更为缺乏。本文采用双面剪切试件,通过2个静载试件和4个疲劳试件的试验研究,考察了粘结长度和胶层厚度等因素对FRP-混凝土界面粘结疲劳性能的影响。通过分析沿粘结长度的FRP应变分布在疲劳循环过程中和疲劳后静载过程中的变化情况,讨论了不同粘结长度和粘结胶层厚度条件下的粘结界面疲劳退化规律和疲劳后静载性能。试验结果表明:胶层树脂-混凝土粘结界面是发生疲劳剥离破坏的薄弱环节;胶层厚度增大时,由于疲劳引起的界面损伤累积发展显著减小,疲劳后静载中胶层厚度较大试件的粘结承载力也更大;粘结长度增大时,界面粘结呈现更为明显的损伤退化,但由于试验粘结长度小于有效粘结长度,疲劳后的静粘结承载力仍更大。

Externally bonded FRP is an important technology for concrete structure reinforcement. However, the current study of fatigue behavior of externally bonded FRP for reinforced concrete structure is not sufficient, in particular, there is more lacking of the study of fatigue degradation and failure mode of FRP-concrete bonded interface. Total 6 double shear specimens, including 2 for static loading test and 4 for fatigue loading test, were manufactured, the effect of bonding length and adhesive layer thickness on the fatigue performance of FRP-concrete bonding interface was studied. By analyzing FRP strain distribution variation along the bonding length during fatigue cycle process and static loading process after fatigue loading, the fatigue degradation of FRP-concrete bonded interface and the post fatigue behavior were discussed under the conditions of different bonding lengths and different adhesive layer thickness. It is concluded from experimental results that the bonding interface between adhesive resin layer and concrete is a weak link of fatigue debonding failure. With the increase of adhesive layer thickness, the development of damage accumulation induced by cyclic load decreases obviously, and the bond capacity after fatigue process increases. The bond deterioration between FRP and concrete becomes more significant when bond length increases. However, due to the experimental bonding length is less than the effective bonding length, static carrying capacity of longer bonding interface is still greater than that of shorter bonding interface after fatigue.