FRP套管砂浆组合加固双轴对称轴压钢构件试验研究

Experimental study on compressed bisymmetrical cross-section steel members strengthened by mortar-filled FRP tubes

利用FRP(纤维增强复合材料)套管和砂浆对受压钢构件进行组合加固以增强构件的抗屈曲性能。通过对不同钢构件截面形状、长细比和端部横向纤维布包裹层数的18根构件的轴压试验,得到加固前后构件的破坏模式、荷载-位移曲线和关键位置的应变变化。试验中构件的破坏模式由加固前的整体屈曲变为加固后的端部裸露钢构件集中变形及FRP套管从端部沿纵向劈裂破坏,加固构件的极限承载力最大提高178%,延性指标最大提高778%。加载过程中构件的不同材料之间会产生滑移现象,但核心钢构件截面基本能保持平截面假定。此方法对大长细比的纯钢受压构件具有更好的抗屈曲加固效果,加固时需注意构件应具有足够的加固段刚度和长度,同时端部应包裹足够的横向纤维布。

FRP （fiber reinforced polymer） tube and mortar are combined to improve the buckling resistance of steel members in compression. Based on axial compression tests of eighteen specimens with different cross-sectional shape and slenderness ratio of steel members, and FRP fabric layers at the end of the specimen, the failure modes, load- displacement curves and strain distributions of each specimen before and after strengthening are achieved. The failure modes of specimens may vary from the global buckling of un-strengthened specimens to the severe local deformation of steel at the end of strengthened specimens and FRP tube splitting longitudinally from the end of the tube. After strengthening, the ttltimate bearing capacity may be increased up to 2.78 times and the ductility may be increased up to 8.78 times of reference specimens. Slipping may occur at the interface between different materials during the loading process, but the cross sections of core steel members may still satisfy the plane cross-section assumption. The strengthening method has a good performance in buckling resistance for those compressed steel members with large slenderness ratios. It should be noticed that enough bending stiffness and length of strengthened segment, and enough lateral FRP fabrics at the end of the specimens are required for a good strengthening effect.