Analysis of a steel structure considering the rotational and translational components of the earthquake excitation

In order to perform a seismic analysis of structure a full description of ground motion is needed. This means that all the six degree of freedom component, three translational and three rotational must take into account. In this research, the influence of rotational component of earthquake excitation to the response of steel structure is examined. In most of studies seismic input is being represented by translational only component of ground accelerations while the rotational one is ignored. This was due to the luck of records which measure the rotational component. Nowadays, technology provides such an instruments and relative records can be found. Elastic design response spectra for rotational components are introduced in codes. Furthermore, the rotational component was not taken into account since its influence in low structures is not significant. The results in response and in internal forces due to rotational component to steel structure are presented. Time history analysis of a symmetrical and non-symmetrical steel structures with and without rotational excitation component is performed. From the numerical results it is shown that the impact of rotational component in response and the internal forces is significant and should not be ignored in design procedure.