基于声发射的钢纤维增强UHPC弯曲断裂损伤机理研究OA

The influence of different steel fiber content(volume fraction)on the bending mechanical behavior and fracture performance of ultra-high performance concrete(UHPC)was studied,and the evolution mechanism of UHPC fracture failure was analyzed based on acoustic emission(AE)energy and peak frequency.The correlation between cumulative AE energy and fracture energy was explored.The research results indicate that there is a nonlinear rela-tionship between the steel fiber content and the fracture performance of UHPC.When the steel fiber content reaches 2.5％,all the fracture performance parameters such as peak bending load,double K model fracture toughness(in-cluding initiation toughness and instability toughness)and fracture energy of UHPC increase to the maximum val-ues;After exceeding this dosage,all the above indicators show a downward trend.The ductility index continues to increase with the increase of steel fiber content.AE energy and peak frequency can effectively characterize the dam-age differences during the fracture process of UHPC beams with different steel fiber contents.High energy AE events mainly occur in the steel fiber pull-out stage;With the increase of steel fiber content,the cumulative AE energy gradually decreases,indicating that steel fibers have a restraining effect on crack propagation to reduce the overall damage of the specimen.The peak frequency of AE signal in the range of 25～200 kHz can be regarded as the domi-nant AE frequency band for the generation and propagation of UHPC cracks,while the 225～375 kHz frequency band mainly corresponds to the steel fiber pull-out and shearing process,revealing the correspondence between the fracture damage stage and AE frequency characteristics.Finally,a significant linear negative correlation is estab-lished between the cumulative AE energy and the fracture energy of UHPC beams,providing a quantitative basis for the non-destructive evaluation of UHPC fracture performance by AE technology.