Research On Dynamic Mechanical Behavior And Constitutive Relation Of Concrete At High Temperature

As a high quality engineering structural material, concrete has been widely used in actual engineering. However, in recent year, the tredence of catching fire of building appears gradually increase. At environment of fire, Concrete structure not only suffered general static and dynamic load, but also subjected to explosion and dynamic load. The mechanical behavior of concrete material is more and more concerned by people under those conditions. So, it is emergent to know the mechanics of concrete on fire and impacting loads at structure design. In this paper, with the support from National Nature Science Foundation of China under grants NO.10602048 and NO.10972187, the dynamic compress mechanical properties and constitutive model of concrete under high temperature are researched deeply. The main research works are as follows:(1) In allusion to thermal inertia, poorer heating uniformity, ect. characteristics of concrete, microwave is used to heat concrete material. The heating and anti-explosion of specimen, temperature uniformity of specimen through heating etc. are researched, and make flash uniformity heating came true. At the same time, high temperature SHPB related experimental technology of concrete material is discussed, such as: thermal protection and fitting of specimen, thermal conduction of concrete specimen with wave-guiding rod after contact, debug of SHPB experimental system, control of incident wave, deal with experimental data, ect. Using ANSYS finite element software, thermal conduction of concrete specimen with wave-guiding rod and their temperature distribution are more analyzed.(2) Using universal material material testing machine, SHPB device and high temperature microwave heating equipment, compress experiments of concrete and cement mortar are carried out at static, quasi-dynamic and 3 speeds impact load under different temperature (20--650℃). Stress-strain curves are obtained at certain condition. And the failure form, strain rate effect and temperature damage effect of concrete and cement mortar are researched.(3) Based on classic damage theory and ZWT visco-elastic constitutive model, and considering the damage evolution of concrete material submitting to Weibull distribution, a damage thermo-visco-elastic constitutive equation at high strain rates is proposed. Through numerical fitting, parameters of the constitutive equation are obtained. A comparison between model prediction and experimental results shows that both of them agree well with each other.