Abstrakt

The soft-storey failure is one of the most typical types of damage observed in buildings during earthquakes. The failure of an upper soft storey of a structure results in large impact load acting on the lower floors and if the resistance of the structural members of the lower storeys is not sufficient it may further lead to progressive collapse of the whole building. The aim of the present paper is to investigate the dynamic behaviour of horizontally deformed steel columns (deformation as the result of earthquake loading) that are additionally subjected to vertical impact load. Steel columns with high slenderness ratio were considered in the study. Both experimental tests and numerical analysis were carried out. In the experiment, impact load was generated by a steel sphere dropped onto a pad of technical clay, so as to simulate nearly plastic impact observed in the reality during earthquakes. The detailed numerical analysis using the FEM was later conducted after verification of the accuracy of the numerical model created. The results of the study indicate that with the increase in the pre-deformation of a column the value of the peak force acting on its top as well as the peak mean normal stress value show a considerable increase trend. Moreover, with the increase in the pre-deformation, the peak horizontal displacement of the middle part of column substantially increases for all height drop values considered. The above conclusions show that the deformation of columns introduced as the result of vibrations due to earthquake loading has a substantial negative influence. The results indicate, however, that even the deformed column is still capable to carry considerable dynamic load before its failure due to stability loss.

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