基于高速DIC的近场冲击下高强混凝土动态压缩性能研究

Investigation of dynamic compression performance of high-strength concrete under near-field impact based on high-speed DIC

为了解近场冲击荷载作用下装配式预制桥梁结构高强混凝土材料的破坏特征及高应变率力学响应特征,采用100 mm大直径霍普金森压杆(split Hopkinson pressure bar,SHPB)对C60及C80两种高强度等级混凝土进行单轴冲击压缩试验。获得了混凝土的应力-应变曲线、动态弹性模量及动态增长因子等动态参数。利用高速数字图像相关(digital image correlation,DIC)技术对混凝土表面应变场进行研究,分析了试样破坏过程中裂纹扩展过程。试验结果表明:在高应变率下,高强混凝土试件的动态压缩强度呈现明显的率效应,但其弹性模量保持恒定;对数函数模型能够较好地表征混凝土的动态强度演化模式;宏观上可以将观察到的破坏模式划分为4种模式:完整试样、轴向劈裂、混凝土爆裂及粉碎;高应变率下,裂缝演化不稳定性增大,其扩展速率随应变率的增大而增大。

In order to gain insight into the damage characteristics and high strain rate mechanical response of high-strength concrete materials in assembled precast bridge structures under near-field impact loading,uniaxial impact compression tests were conducted on C60 and C80 high-strength concrete using a 100 mm large-diameter split Hopkinson pressure bar(SHPB).Dynamic parameters such as stress-strain curves,dynamic modulus of elasticity and dynamic increase factor of the concrete were obtained.The high-speed digital image correlation(DIC)technology was used to study the strain field on the concrete surface and analyze the crack propagation process during the failure process.Test results show that:the dynamic compressive strength of high-strength concrete specimens under high strain rate shows obvious strain rate effect,but its modulus of elasticity remains constant.And the logarithmic function model can better characterize the dynamic strength evolution pattern of high-strength concrete under high strain rate.Macroscopically,the observed damage patterns can be classified into four modes:intact specimen,axial splitting,concrete bursting,and crushing.At high strain rates,the instability of crack and its expansion rate increases with strain rate.