Experimental Study On Dynamic Bond Properties Between Steel Reinforcement And Concrete At And After Elevated Temperature

In recent years,with the developing utilization of energy in daily life,various explosion and fire accidents are happening more and more frequently.These extreme loads seriously affected the serviceability of structures and even cause progressive collapse which will lead to catastrophic consequences.Consequently,it is necessary and urgent to carry out experimental study on mechanical properties of reinforced concrete under high temperature and impact loads.In the current studies,experiments are mainly based on separate aspects of impact damage and degradation at high temperature.However,researches on structure mechanical properties under the couple effect of impact loads and high temperature are very limited,especially with dynamic bond properties at high temperature.Based on this situation,high performance drop hammer impact test machine combined with self-developed inertia-force-eliminated conversion beam device in Hunan University were used to study the dynamic bond properties of reinforce concrete at high temperature.Numerical simulations of static tests were also carried out by using ABAQUS.The main research work in this paper including following aspects:(1)A inertia-force-eliminated conversion beam device for drop hammer impact tensile tests was developed.Combined with drop hammer impact test machine,the device can transform the vertical impact loads into horizontal tensile loads while the inertia effect is eliminated.(2)Static tests of bond properties between steel reinforcement and concrete at and after elevated temperature were carried out to analyze the effect of temperature on failure pattern,bond strength and bond-slip curves.Statistical analysis was also carried on to investigate the changing law of bond properties at and after elevated temperature.Static computational formula and constitutive model were established based on these statistical data.(3)Drop hammer impact tests of bond properties between steel reinforcement and concrete at and after elevated temperature were carried out to analyze the effect of temperature and impact velocity on failure pattern,bond strength and bond-slip curves.The coupling effect of thermal softening and strain rate effect were discussed.Dynamic model of bond properties was also established based on proposed static model.(4)Temperature field model and computational model were established by using ABAQUS/Explicit.Comparison between simulation results and test results was made to verify the reliability of proposed model,and accordingly simulate variation of concrete stress and effect of concrete strength.