玄武岩纤维增强聚合物筋钢纤维高强混凝土梁受弯试验及裂缝宽度计算方法研究

纤维增强聚合物(FRP)筋混凝土梁受弯挠度过大、裂缝过宽等缺陷严重影响其正常使用性能,为此,将具有优良抗裂与阻裂性能的钢纤维混凝土用于FRP筋混凝土梁,可以有效限制其挠度与裂缝的发展。通过12根玄武岩纤维增强聚合物(BFRP)筋/钢筋钢纤维高强混凝土梁的受弯性能试验,研究了钢纤维体积率、受拉区钢纤维高强混凝土层厚度、BFRP筋配筋率对BFRP筋钢纤维高强混凝土梁裂缝分布与宽度的影响。结果表明,钢纤维的加入能够有效抑制BFRP筋高强混凝土梁的裂缝开展,减小裂缝间距、宽度和裂缝宽度差异性,当荷载为100 kN时,钢纤维体积率为0. 5%~2. 0%的钢纤维高强混凝土梁的裂缝宽度减小了25. 22%~54. 78%,裂缝宽度标准差减小了10. 00%~68. 18%;当受拉区钢纤维混凝土层厚度达到梁截面高度的57%时,其阻裂与限裂效果与全截面掺加钢纤维的效果接近,表明在受拉区中掺加钢纤维以限制BFRP筋混凝土梁裂缝的发展是经济可行的。基于试验和相关文献研究结果,提出了考虑钢纤维影响的BFRP筋钢纤维高强混凝土梁最大裂缝宽度的建议计算方法,该建议方法的计算值与试验值吻合良好。

Bending experimental study and crack width calculation method of high-strength concrete beams reinforced with BFRP bars and steel fiber

Large deflection and crack width significantly affect the serviceability of concrete beams reinforced with FRP bars. The addition of steel fibers can effectively restrain the development of deflection and crack width of FRP bar-reinforced concrete beams. In order to investigate the influences of steel fiber volume fraction, depth of steel fiber reinforced concrete layer of tensile zone and ratio of basalt fiber reinforced polymer（BFRP） reinforcement on distribution and width of flexural crack of high-strength concrete beams, 12 specimens were cast and tested. The results indicate that the addition of steel fibers restrains the development of crack space and width. Compared with the beam reinforced with BFRP bars, when the applied load reaches to 100kN, the beam reinforced with BFRP bars and steel fibers with the fraction of 0.5%~2.0% can reduce the crack width by 25.22%~54.78% and the deviation of crack width by 10.00% 68.18%. When the depth of steel fiber reinforced concrete layer is 0.57 times of the height of specimens, the steel fibers produce the same effect on restraining cracks as fully steel fiber reinforced beams. This indicates that adding steel fibers in tensile zone is an economical and effective way to restrain the propagation of cracks in BFRP bars-reinforced concrete beams. Based on the test and theoretical analysis, the calculating method, which can be used for evaluating the crack width of high-strength concrete beams reinforced with BFRP bars and steel fiber, was proposed. The calculated values have good agreement with the test results.