基于细观模型的超高性能钢纤维混凝土SHPB试验数值模拟

超高性能钢纤维混凝土是一种极具创新性的水泥基复合材料,具有优异的力学性能,在结构抵抗极端荷载方面潜力突出.为研究超高性能钢纤维混凝土动态力学性能,利用LS_DYNA软件建立了由砂浆和钢纤维组成的细观数值模型.首先,通过静态压缩和劈裂试验对细观模型进行了验证.其次,对霍普金森压杆(SHPB)试验进行了数值模拟,并在细观尺度上解释了应力-应变历程,研究了钢纤维含量对超高性能钢纤维混凝土动态性能的影响.研究结果表明,该模型能够很好地预测超高性能钢纤维混凝土的静态和动态性能;当钢纤维在合理范围内(0%–2.5%)时,超高性能钢纤维混凝土动态强度随着钢纤维体积率的增加而显著增大;然而,超高性能钢纤维混凝土动态增强因子低于传统混凝土材料.同时,定量分析了钢纤维增强效果,并在试验和数值模拟的基础上推导了超高性能钢纤维混凝土的动态本构关系.

Numerical simulation of SHPB test of ultra-high performance fiber reinforced concrete with meso-scale model

Ultra-high performance steel fiber-reinforced concrete is an innovative cement-based composite material with excellent mechanical properties and outstanding potential in resisting extreme loads.In this study,a meso model of ultra-high performance steel fiber-reinforced concrete specimen,which consists of cement mortar and fibers,is developed to numerically simulate Split Hopkinson pressure bar(SHPB)tests for investigation of behavior of ultra-high performance steel fiber-reinforced concrete material under impact loading.The software LS_DYNA is used to perform the numerical simulation of dynamic tests.A good agreement is observed between the simulated results and experimental results.After the meso model is validated with static compression and split tension tests,SHPB tests are numerically modelled and the stress-strain history is interpreted in the meso-scale level.The influence of fiber on ultra-high performance steel fiberreinforced concrete in dynamic tests is investigated.Within a reasonable range of steel fiber volume ratio(optimum volume ratio ranges from 0%–2.5%for micro steel fiber),the dynamic strength of ultra-high performance steel fiberreinforced concrete increases significantly with the increase of steel fiber volume ratio,however,the contributions of fibers to Dynamic Increase Factors(DIF)of ultra-high performance steel fiber-reinforced concrete are constantly lower than those of conventional concrete material.The proposed model qualitatively and quantitatively predicts the material static and dynamic behaviors,and also gives insights on the fiber reinforcement effect in the concrete matrix.In this study,the dynamic constitutive relationships of ultra-high performance fiber-reinforced concrete are derived for predicting the dynamic strength of ultra-high performance fiber-reinforced concrete with different steel fiber volume ratios and strain rates.