The influence of vibration duration on the structure of irregular RC buildings

Abstract

In the twenty-first century, the seismic design of buildings seems to have become a fully recognised topic. There are guidelines and standards which should be taken into account by designers in seismic areas. Designers using modern international guidelines have ascertained that the behaviour of structures is not as expected. This may be the result of not taking into account the duration of the shock. The duration of surface vibrations could be one of the basic reasons why some buildings collapse or suffer severe damage to bearing systems as a result of long-duration earthquakes despite being properly designed in accordance with current understanding. Another primary reason for such collapse or damage is that some buildings in seismic areas have irregular structural systems that are sensitive to torsional vibrations. In this paper, a five-storey, irregular-shaped RC building model was subjected to different types of excitations: mining tremors, short-duration earthquakes, long-duration earthquakes. The first stage was a modal analysis based on in situ measurement. After model verification using in situ measurements, the building was then subjected to the three forms of excitation. Numerical studies were performed using a verified FEA model of the building in the time domain. The results of the calculations prove that the duration of the intensive phase of extortion is one of the reasons for the lack of building collapse in mining areas. In cases of mining shocks with a short duration of surface vibration, damage to buildings may occur which does not threaten the safety of their construction. Building collapses occur with earthquakes which are characterised by a much longer duration of the intensive phase of excitation compared to mining shocks. The results of in situ observations of RC structures that have survived a history of mining shocks of varied intensities confirm the results of numerical analyses.