CFRP布端绕双杆自锁加固混凝土窄梁抗弯试验

Flexure tests on narrow concrete beams strengthened with CFRP sheets end-locked by winding around twin-rods

为了抵抗粘贴碳纤维增强聚合物基复合材料(CFRP)加固钢筋混凝土结构中常见的剥离破坏,发明了将CFRP布端部以特定方式绕平行双杆实现自锁的方法。鉴于窄梁截面宽度有限,提出将CFRP布贴梁受拉底面布置后,用安装在梁侧面的双L形端锚装置固定双杆,形成侧锚底贴加固方案。完成了5根混凝土强度较低的矩形截面梁四点弯曲试验,其中4根采用上述锚固方式抗弯加固,检验了锚固效果,考察了CFRP布宽度及其沿全长与梁底面是否粘结对加固效果的影响。试验结果表明,采用本文方法进行加固后,端部剥离得以避免,中部剥离即使发生,或在无粘结加固梁受力后期,CFRP布仍能承担较大拉力,因此,极限荷载较对比梁有明显提高。比较而言,CFRP布与梁底有粘结时加固效果更好,CFRP布宽度加大也对提高承载力有益。

In order to prevent the debonding failure occurring in reinforced concrete beams strengthened with carbon fiber reinforced polymer（CFRP）sheets,a technique of self-locking anchorage which anchors the ends of CFRP strips by winding around twin rods in parallel in a particular way was invented.In view of the limited width of a narrow beam,a scheme with side anchorage and bottom bonding was proposed,i.e.,placing the CFRP to the beam bottom and using bolts to fix the double L-shaped end device with twin rods to the beam side.Five rectangular beams with lower concrete strength were tested in four-point bending,including four beams strengthened in flexure by using above self-locking anchorage method.The feasibility of the new scheme was validated and the influence of the strip width and whether it is bonded with the bottom of beam were studied.The test results show that the strengthening method in this paper can avoid the end-debonding,and the strip can still carry large tension even when the intermediate debonding happens,or in the late loading stage of unbonded strengthened beams.Therefore,the ultimate load is obviously promoted as compared with the control beam.Comparatively,the specimens with bonded strips perform better than that with unbonded,and increasing the strip width is beneficial to enhancing the load bearing capacity of beams.