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采用大连理工大学的混凝土大型静、动三轴试验系统,对经受200℃―600℃高温后的C30普通混凝土试件进行了等比例三轴压试验。观察了各温度后试件的破坏形态,测得了三轴强度、峰值应力点处的应变及应力-应变曲线。试验表明,高温后三轴强度和峰值应力点的应变较单轴状态有较大的增长,中间主应力对多轴强度及峰值应力点处应变的影响较为显著。随着温度的升高,三轴抗压强度的降低程度与单轴下不同,八面体应力空间正应力、剪应力破坏强度与单轴抗压强度的相对值在200℃后加速增大。分析了温度和应力比对破坏强度的影响,在八面体应力空间建立了破坏强度与应力比、温度的关系式,可以为复杂应力状态下高温后混凝土的力学分析提供试验和理论基础。
Using the large-scale static and dynamic triaxial test system of concrete in Dalian University of Technology, the triaxial compression tests of C30 normal concrete specimens subjected to high temperature from 200 ℃ to 600 ℃ were carried out. The failure modes of the specimens after each temperature were observed. The triaxial strength, strain at the peak stress point and the stress-strain curve were measured. The experimental results show that the strain of triaxial strength and peak stress at high temperature increase more than that of uniaxial state. The influence of middle principal stress on multiaxial strength and strain at peak stress is significant. With the increase of temperature, the decrease of triaxial compressive strength is different from that of uniaxial compressive strength. The relative values of normal stress, shear stress rupture strength and uniaxial compressive strength of octahedral stress space increase rapidly after 200 ℃. The influence of temperature and stress ratio on the failure strength is analyzed. The relationship between failure strength and stress ratio and temperature is set up in the octahedral stress space, which can provide the experimental and theoretical basis for the mechanical analysis of post-high temperature concrete under complex stress conditions.