外贴纤维布加固钢筋混凝土梁的抗剪试验研究

针对汶川地震灾区大量由于剪切损伤亟待修复的结构,研究了外贴玻璃纤维布(GFRP)或碳纤维布(CFRP)加固矩形截面梁的剪切破坏问题.通过对5根钢筋混凝土梁的加固试验,研究外贴纤维布对加固梁的破坏形态、刚度变化,裂缝开展情况及极限承载力的影响,并对不同的加同方法、配箍率和截面高度对抗剪加固效果的影响进行了分析.试验结果表明,外贴纤维布加固可明显提高钢筋混凝土梁的抗剪承载力和变形能力,并使梁的整体刚度得到提高;相对于CFRP加固,GFRP可显著提高加固梁的延性,增加纤维布的利用率.试验梁的截面高度越小,CFRP加固后其变形能力明显提高,但极限承载力却有所降低;同时,配箍率越大,加固梁的开裂倚载和极限荷载提高越明显,但加固梁的延性越差.最后,根据混凝土构件中各材料的应力-应变关系和变形协调原理,建立了实用的理论计算公式,理论计算结果与试验结果符合较好.

Experimental Study on RC Beams Strengthened with Externally Bonded FRP Sheets

In order to repair many structures damaged in Wenchuan earthquake, using carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) to repair the reinforced concrete (RC) beams was studied. The failure types, stiffness change, crack developing characteristics and shear resistance were investigated. Beam size, stirrup ratio, FRP type and arrangements of sheets along the shear span were analyzed during experimental study. The test result indicated that CFRP or GFRP can increase the shear resistance and deformability greatly, and the rigidity of strengthened beams also increases obviously. Compared to strengthening with CFRP, the GFRP strengthening method increase the deformability and the utilization ratio of strengthening material. The shear resistance increases with the beam height, but not fit for the deformability. Increasing stirrup ratio can delay the crack appearing obviously, improve the cracking load and ultimate strength of strengthened beam, but reduce the ultimate deflection greatly. Finally, according to the analysis of test data, the theoretical and practical formula for calculating the bearing capacity of RC beams strengthened with FRP sheets was established. The results showed that the theoretical calculation is in accord with the experimental data.