短切玄武岩纤维混凝土简支梁正截面受弯性能试验研究

Experimental study on flexural behavior of normal section of simply-supported chopped basalt fiber-reinforced concrete beams

为研究短切玄武岩纤维混凝土(chopped basalt fiber reinforced concrete,CBFRC)梁的受弯性能,以短切玄武岩纤维长径比、局部纤维层高度和纵筋配筋率为主要研究变量,对12根CBFRC梁进行了四点弯曲静力试验,通过观测其裂缝开展和破坏模式,分析了各参数对CBRFC梁的受力性能增益效果。结合试验结果,给出了考虑纤维影响的CBFRC梁开裂弯矩和短期刚度的计算公式。研究结果表明:短切玄武岩纤维能有效改善混凝土的力学性能,可以较好地抑制裂缝开展,提高混凝土梁的承载力;当纵筋配筋率为0.91%~2.54%时,开裂荷载提高了16.6%~25.5%,屈服荷载提高了0.0%~8.9%,且提高幅度降低;纤维长度为6~18 mm时,开裂荷载提高了16.5%~53.8%,屈服荷载提高有限(2.9%~5.8%);随局部纤维层高度增加,梁的开裂弯矩提高、增益效果明显,当纤维层高度达到试验梁截面高度的35%时,才可发挥对应的全截面纤维梁的增强阻抑效果;建议的开裂弯矩、短期刚度的改进计算模型均与试验结果有较高的吻合程度,并通过已有的试验数据验证了该改进模型的准确性及适用性。

To investigate the flexural behavior of chopped basalt fiber-reinforced concrete(CBFRC)beams,a total of twelve beam specimens were tested under four-point bending,with the test variables being the aspect ratio of chopped basalt fibers,the depth of fiber-reinforced layer and the longitudinal reinforcement ratio.The crack development and failure modes were observed,and the improvement in the mechanical performance of CBFRC beams by different parameters was also analyzed.Considering the reinforcing effects of fibers,the improved calculation formulas for both the cracking moment and the short-term stiffness were proposed based on the test results.The experimental results show that basalt fiber can improve the mechanical performance of concrete and effectively control crack development,thereby improving the bending capacity.When the longitudinal reinforcement ratio is 0.91%-2.54%,the cracking capacity is increased by 16.6%-25.5%,the yield capacity is increased by 0.0%-8.9%,and the increase amplitude shows a downward trend.With the fiber length is 6-18 mm,the cracking capacity is increased by 16.5%-53.8%,but the yield capacity is not significantly increased(i.e.,by only 2.9%-5.8%).As the depth of fiber-reinforced layer increases,the corresponding cracking moment and the cracking-control ability also increase.When the depth of fiber-reinforced layer is at least 0.35 times of the total height of the beam,the basalt fibers achieve good performance on restraining cracks.The performance is similar to that of concrete beams fully reinforced by basalt fibers.The improved calculation models of cracking moment and the short-term stiffness proposed in this paper are in good agreement with the test results.The accuracy and feasibility of the improved models are verified by the test data from the existing studies.