1.Air Force Engineering University;2.Central Theater Air Force Support Department
由于实验的复杂性,高温后混凝土在复杂应力状态下的动态力学性能研究一直较少,但在建筑物火灾和国防军事防护工程中,混凝土结构多处于多轴应力和冲击荷载的共同作用下。为研究静动组合荷载下混凝土高温后双轴动态力学性能,采用真三轴静、动力综合加载实验系统,使用真三轴试验机预先施加双轴轴压,再利用SHPB试验装置,分别对常温(25 ℃)和200、400、600、800 ℃高温后混凝土试件施加冲击动载,发现了双轴应力状态下混凝土在高温后的动态力学性能规律性。试验结果表明：温度变化是影响高温后混凝土双轴动态力学性能的主要因素,应变率变化是次要因素；当温度大于400 ℃时,应力—应变关系曲线出现屈服平台,此时混凝土韧性较低温时有显著提高。200 ℃是高温后混凝土双轴动态抗压强度的转折温度,当温度继续升高时,双轴动态抗压强度明显下降。
Due to the complexity of the experiment, the research on the dynamic mechanical properties of concrete under complex stress conditions after high temperature has been less, but in building fires and defense and military protection projects, concrete structures are mostly under the combined action of multiaxial stress and impact loads. In order to study the biaxial dynamic mechanical properties of concrete after high temperature under combined static and dynamic loads, a true triaxial static and dynamic comprehensive loading experimental system is used. A true triaxial test machine is used to apply biaxial axial pressure in advance, and the SHPB test device is used to apply dynamic load to temperature respectively (25 ℃) and 200, 400, 600, 800 ℃ high-temperature concrete specimens, found that the biaxial stress state of the dynamic mechanical properties of concrete after high temperature regularity. The test results show that: temperature change is the main influencing factor of the biaxial dynamic mechanical properties of concrete after high temperature, and strain rate change is the secondary factor; when the temperature is higher than 400 ℃, the stress-strain relationship curve shows a yielding platform, and the concrete toughness is significantly improved relatively low temperature. 200 ℃ is the turning temperature of biaxial dynamic compressive strength of concrete after high temperature. When the temperature continues to increase, the biaxial dynamic compressive strength decreases significantly.