腹板开大洞口RC梁的体外加固技术对比试验研究

Comparative Study on External Strengthening Methods of RC Beams with Large Web Openings

试验研究不同加固方式对腹板开大洞口钢筋混凝土(RC)梁的加固效果.结果表明,洞口破坏了梁的抗剪机制,使其承载力与刚度大幅降低,发生脆性破坏.3种加固方法均能有效限制洞口角部斜裂缝开展,提高其抗剪承载力.碳纤维复合材料(CFRP)加固对梁刚度提高不明显,但加固梁延性显著增加.粘贴钢板加固易发生钢板局部膨出,上肢混凝土压溃,破坏脆性.带肋钢板加固使梁刚度削弱基本恢复,承载力大幅提高.带肋钢板加固梁的破坏较为延性,且加固效果有望因楼板翼缘而进一步改善.开洞尺寸是影响加固效果的最主要因素,一定范围内体外加固能够使梁受力性能得到恢复,超出则加固效果明显削弱.

Structural effectiveness of three external strengthening systems is investigated experimentally on reinforced concrete beams with large web openings. Shown by the results,shear resistance of non-strengthened beams is damaged greatly by the opening,which caused remarkable reduction of load bearing capacity ＆ stiffness,and eventually led to brittle shear failure. The three strengthening methods are all effective in bridging diagonal corner cracks and enhancing shear resistance of the beams. Carbon fiber reinforced polymer（ CFRP） confinement provides the strengthened beam with considerable ductility while the stiffness is barely changed. External bonded plain steel plate is less promising for brittle failure of concrete crushing of the top chord as a whole,preceded by buckling of the plate. Due to large increase of load capacity,stiffness restoration and considerable ductility,the strengthening system using ribbed steel plate seems to be the best solution,which can be expected to be more efficient in field application taking into account the contribution of slab flange. The size of web opening is a key parameter in strengthening effects. Damage caused by the opening within a certain limit of size can be fully recovered by external strengthening,while the strengthening efficiency is likely to drop rapidly thereafter.