低速冲击下纤维混凝土梁的动力学特征与断裂耗能研究

Dynamic characteristics and fracture energy dissipation of fiber reinforced concrete beams under low-velocity impact

随着各类型短切纤维的生产成本的降低,纤维混凝土得到大规模发展且应用领域不断扩展,为保证纤维混凝土在复杂环境的服役安全,该研究分别对素混凝土(plain concrete,PC)梁与纤维长度为6~8 mm且体积掺量均为0.30%的碳纤维(carbon fiber,CF)、玻璃纤维(glass fiber,GF)和玄武岩纤维(basalt fiber,BF)混凝土梁进行低速冲击试验,研究了普通混凝土梁和纤维混凝土梁的抗弯失效机理及断裂耗能。通过高速摄像机记录各试件梁的断裂破坏过程,提取并分析对比了跨中竖向位移时程曲线、加速度时程曲线及拉压应变时程曲线。详细分析了锤头冲击力和惯性力,并得到等效变形力-位移曲线,计算出各纤维混凝土梁断裂耗能。结果表明,各试件梁的破坏形态均为典型的弯曲破坏,均形成一条竖向主裂缝。GFRC梁断裂消耗的能量最多,相比于PC梁提高了88%。CFRC梁和BFRC梁消耗的能量分别相对于PC梁提高了43%和18%。该研究对不同类型纤维混凝土受弯构件在低速冲击工况下的力学性能与能量消耗方面的定量化研究结果可为纤维混凝土的工程推广应用提供参考。

With the reduction of the production cost of various types of chopped fiber,fiber reinforced concrete has been developed on a large scale and its application fields are expanding.In order to ensure the service safety of fiber reinforced concrete in complex environment,the concrete beam and carbon fiber(CF)with the fiber length of 6-8 mm and the volume content of 0.30%were analyzed.The low velocity impact tests of glass fiber(GF)and basalt fiber(BF)concrete beams were carried out to study the bending failure mechanism and fracture energy consumption of ordinary concrete beams and fiber reinforced concrete beams.The fracture process of each beam was recorded by high-speed camera,and the vertical displacement time history curve,acceleration time history curve and tension compression strain time history curve were extracted and analyzed.The impact force and inertia force of hammerhead were analyzed in detail,and the equivalent deformation force displacement curve was obtained,and the fracture energy consumption of each fiber reinforced concrete beam was calculated.The results show that the failure mode of each specimen is typical bending failure,and a vertical main crack is formed.The energy consumption of GFRC beam is the most,which is 88%higher than that of a plain concrete(PC)beam.The energy consumption of CFRC beam and BFRC beam is 43%and 18%higher than that of the PC beam,respectively.In this paper,the quantitative research results of mechanical properties and energy consumption of different types of fiber reinforced concrete flexural members under low velocity impact condition can provide reference for the engineering application of fiber reinforced concrete.