Dynamic Analyses Of RC Columns Subjected To Lateral Impact Loading

Reinforced concrete members are currently widely adopted in not only various buildings but also structures that are more easily vulnerable to ships and vehicles,such as harbors and bridges.Compared to conventional static or quasi-static loadings including self-weight,live loads and dead loads,much larger energy would be released by impact loadings attributed to its instantaneity and intensity.Collapse in reinforced concrete columns,that are responsible for loads bearing,could lead to continuous collapse of the whole structure,bringing catastrophe.Deep research on the dynamic response of columns under impact loadings,thus,is vital in both engineering and theoretical aspects.(1)12 specimens with three kinds of square sections of sides of 120 mm,150mm and 180 mm were established to conduct static load tests,impact load tests and residual load capacity tests.Moreover,axial load was applied and load point was located at the top end of the column.One filtering method based on Fourier Transform was firstly put forward to get the failure modes,load-displacement curves and dynamic increase factor.Furthermore,changes in flexural bearing capacity and displacement of columns subjected different impact masses and damage were analyzed.Finally,the intact impact process was thoroughly presented by the combination of result of photographs about column head-vehicle from high-speed camera and time history curve of impact force.(2)Numerical Simulation was carried on in software LS-DYNA,where consistent result was obtained.The principles and process of applying axial load to columns by decreasing the temperature were introduced innovatively,and rationality as well as efficiency has been verified.According to the results,besides the influence of stiffness and impact mass on strain as well as energy distribution,the energy absorption and discharge during this period were also discussed in detail.It can also be shown that real dynamic resistance could be got through eliminating the inertial effect,which cannot be neglected,by taking advantage of modal analysis.Based on PEEQ result,suggestions on strengthening regions were raised.(3)It cannot be denied that displacement is related to impact mass and velocity simultaneously,113 specimens then were analyzed in LS-DYNA,with sections,mass and velocity being parameters,response surfaces of maximum displacement at load point were obtained finally.The least square method was used in programming to fit above surface,a precise and accurate equation was accomplished.Moreover,the equation could solve the maximum displacement of the loading point on the specified column with impact mass and velocity given.