Vibration studies on an impact loaded reinforced concrete structure

Both earthquakes and aircraft impacts induce vibrations that propagate throughout the entire building. These vibrations need to be considered in designing SSCs (Structures, Systems and Components). So far, mainly linear calculation methods have been in use in practice and thus the codes and standards consider only damping ratios for linear assessments. Induced vibrations, especially in damaged concrete structures, have not been studied extensively enough. Especially experimental data on damping properties of damaged reinforced concrete are needed. One of the main issues is the assessment and modelling of damping in such structures. Recently, within IMPACT project, a new type of test series considering vibration propagation has been initiated at VTT. The target is a U shaped reinforced concrete structure with two parallel walls connected to a floor slab. In order to get information on vibration propagation in damaged concrete at different levels of damage grades the same structure was tested three times. At each time the mass of the deformable stainless steel missile was 50 kg and the impact velocity was about 110 m/s. The test arrangement and measurements are presented in a joint paper by Vepsä et al. (2015). In this study the numerical results, accelerations, displacements, their response spectra and strains, are compared with experimental measurements. Two finite element methods, Abaqus and an in-house code, were used in computations.