GFRP筋混凝土梁受弯性能试验

为改善GFRP(glass-fiber reinforced polymer)筋混凝土梁裂缝宽度较大的缺陷,提出一种将GFRP筋穿入金属波纹管并灌注水泥基高强灌浆料的新型构造措施,内部高强水泥基灌浆料与GFRP筋的黏结性能较好,共同参与受拉,外部金属波纹管可约束内部黏结裂缝的扩展,并增强与混凝土之间的黏结作用,进而减小GFRP筋混凝土梁的裂缝宽度.为验证其可行性,对配置钢筋、拉挤GFRP筋以及新型构造措施GFRP筋的6根简支梁开展了单调加载受弯试验,考察了GFRP筋混凝土梁在正常使用极限状态下的裂缝分布、平均裂缝间距以及平均裂缝宽度的发展规律.试验结果表明:与普通拉挤GFRP筋相比,新型构造措施可减小梁在使用阶段的裂缝宽度,延缓顺筋裂缝的出现;新型构造措施GFRP筋混凝土梁可满足各国规范0.5 mm最大裂缝宽度的限值规定,普通GFRP筋混凝土梁则不能满足要求;当GFRP筋配筋率接近或大于界限配筋率时,梁表现为首先混凝土受压破坏、最后FRP纵筋受拉断裂的失效模式,其受弯承载力高于钢筋混凝土梁,破坏前有较大的变形能力,平均挠跨比约为1/56.

Flexural experiment of concrete beams reinforced with GFRP bars

To reduce the crack width of concrete beams reinforced with glass-fiber reinforced polymer(GFRP) bars, this paper proposes a new type construction measure for FRP bars which is fabricated by inserting the GFRP bars into the metal corrugated pipe and filling the interspace with high strength cement-base grouting materials.The internal high-strength cement-based grouting material has good bonding performance with GFRP bars and participates in the pulling, while the external metal bellows can restrain the expansion of internal cohesive cracks and strengthen the bonding effect with concrete. Therefore, the crack width of concrete beams reinforced with GFRP bars is reduced. To verify the feasibility, a monotonic loading flexural test was carried out on six beams reinforced with steel bars,extruded GFRP bars, and the new type GFRP bars, respectively.The effects of longitudinal bars on the crack distribution, average crack spacing, and crack width were investigated. The experimental results show that the new type construction measure can reduce the crack width of beams in the serviceability limit state and delay the appearance of the cracks along the bars compared with general extruded GFRP bars.Besides, the beams treated with the new type construction measure met the code requirement of the maximum crack width of 0.5mm, while the ordinary concrete beams reinforced with GFRP bars did not. The failure modes of beams reinforced with GFRP bars began with concrete crush in compressive zone,and the final destruction were the rupture of longitudinal FRP bars. The flexural capacity of beams reinforced with GFRP bars was higher than that of RC beams and expressed the good deformability before final destruction, in which the average deflection span ratio approximately reached 1/56.