为研究配筋钢纤维混凝土结构在断裂破坏全过程中的力学响应及断裂损伤机理,基于内聚力单元提出了一种配筋钢纤维混凝土结构数值模型的建模方法,其中内聚力单元被用于表征钢纤维混凝土潜在断裂面及钢筋—混凝土界面。基于所建立模型,提出了综合考虑复合损伤作用、缝间摩擦以及纤维桥接效应的钢纤维混凝土本构模型。此外,在经典钢筋—混凝土界面黏结滑移模型的基础上,补充考虑界面法向分离及其对切向黏结性能弱化作用,建立了一种改进的钢筋—混凝土界面本构模型。为验证模型准确性,设计了一组配筋钢纤维混凝土梁的四点弯曲试验。通过对比模拟与试验结果,所建立的数值模型具有一定的适用性,能够较好的模拟配筋钢纤维混凝土的断裂破坏全过程力学响应以及相应的断裂形态。基于所建立本构模型的特点,进一步研究了纤维掺量和钢纤维混凝土缝间摩擦系数对结构承载性能的影响。研究结果表明,当纤维掺量较小以及摩擦系数取值不合理时(系数偏小或不考虑摩擦),结构的承载性能在塑性阶段会受到显著影响,主要表现为承载能力下降且脆性增大。

To investigate the mechanical response and fracture mechanism of the steel fiber reinforced concrete (SFRC) structure, a numerical modeling method based on the application of cohesive elements was proposed. In the proposed model, cohesive elements were used to characterize the potential fracture surfaces and the rebar-concrete interfaces. By considering the mixed-mode damage relation, friction, and the bridging effect of fibers, a constitutive model of SFRC potential fracture surfaces was developed. Besides, based on the traditional bond-slip relation, a modified constitutive model of the rebar-concrete interface was proposed by considering the separation in the normal direction. To validate the proposed model, a group of SFRC four-point bending experiments was carried out. Through the comparison between the simulation and experiments, the proposed model was proved to be able to simulate the mechanical response and the fracture behavior of the SFRC structure appropriately. According to the characterization of the SFRC constitutive model, the influence of the fiber content and concrete friction factor on the structure bearing capacity was studied. It is found that when the fiber content is small or the friction factor is unreasonable, the bearing capacity and the ductility would decrease significantly.

TU318??????

国家自然科学基金项目（面上项目，重点项目，重大项目）