FEASIBLITY EVALUATION FOR A PREDEFINED SEISMIC RESISTANCE OF STRUCTURES

Nowadays seismic resistant structural design is based on force analysis and on representing the earthquake effect as equivalent static forces set as elastic response spectra (response spectrum method). These response spectra link the law of earth motion to the absolute acceleration of the structure's model. This approach takes no account of either the effect of intense motion duration or of the plastic behavior of the structure. The frequency content and the duration of earth oscillations immediately influence the energy taken in by the building and causing damage to its elements. In theoretical terms, the input energy depends on the model of the structure in question. The input energy is determined by a dynamic calculation for the selected model or by theoretical assessment. Then, the energy is compared to the energy capacity, i.e. maximum energy which can be conveyed to the building before it collapses. Conventionally, the energy capacity is compared to the plastic component of the input energy (absorbed by the building). This forms the basis for the energy method of seismic structural design. The present paper considers a seismic resistance feasibility calculation technique employing non-linear statistical analysis based on the energy-centered approach. Non-linear static and non-linear dynamic calculations were run for a three-story frame. The two methods were benchmarked against each other, the importance of the higher modes of vibration was exposed, the importance of analyzing their influence on the system's response was emphasized