存在薄弱界面的CFRP加固RC梁疲劳性能试验

Fatigue Performance Test of CFRP-Strengthened RC Beams with Weak Interfaces

通过6根存在弱界面的CFRP加固RC梁和1根对比梁的弯曲疲劳试验,研究弱界面对加固梁的疲劳破坏形态、疲劳变形性能以及疲劳寿命的影响。结果表明,有弱界面CFRP加固梁的疲劳破坏形式以CFRP剥离破坏为主,同时部分梁发生保护层脱落、受拉钢筋或CFRP疲劳断裂、U型箍剥离等破坏。界面削弱程度越重,保护层厚度越小,加固梁随疲劳次数增加带来的疲劳损伤发展速度越快,疲劳寿命越低。加固量的增加能有效降低CFRP内的应力水平,控制疲劳损伤发展,并由此大幅提高加固梁的疲劳寿命。界面削弱严重时,或弱界面靠近CFRP-混凝土黏结面时,疲劳荷载下保护层易受损脱落,引起纵向CFRP局部挤压断裂及U型箍剥离。

A total of 6 CFRP strengthened RC beams with weak interfaces and 1 reference beam are tested under flexural fatigue loading to investigate the effects of weak interfaces on fatigue performance of strengthened beams. The results show that CFRP debonding is the dominant failure mode of the strengthened beams with weak interfaces, and other failure modes include concrete cover delamination, rupture of rebar or CFRP and peeling off of U-shaped CFRP stirrups. The damage accumulates more rapidly in beam specimens with weaker interface or thinner concrete cover, which consequently leads to a shorter fatigue life. Increasing the amount of flexural CFRP can effectively reduce the stress level in CFRP, control the development of fatigue damage, and thus greatly extend the fatigue life of the beams. When the interface is weakened seriously, or the weak interface is close to the CFRP-concrete bond surface, the concrete cover is vulnerable to fatigue damage and easily to delaminate, leading to local squeezing and fracture of flexural CFRP bundles and debonding of U-shaped stirrups.