Response Spectra Evaluation Including Pounding Effect
Most of the existing seismic resistant design codes are based on the response spectrum theory. The influence of inelastic deformations can be evaluated by considering inelastic type of resisting force and then the inelastic spectrum is considerably different from the elastic one. Also, the influence of stiffness degradation and strength deterioration can be accounted for by including more precise models from material point of view. In some recent papers the corresponding changes in response spectra due to the P- Ä effect are discussed. The experience accumulated from the recent earthquakes indicates that structural pounding may considerably influence the response of structures and should be taken into account in design procedures. The most convenient way to do that is to predict the influence of the pounding on the response spectra for accelerations, velocities and displacements. Generally speaking the contact problems such as pounding are characterized by large extent of nonlinearity and slow convergence of the computational procedures. Thus obtaining spectra where the contact problem is accounted for seems very attractive from engineering point of view because could easy be implemented into the design procedures. However it is worth nothing that there is not rigorous mathematical proof that the original system can be decomposed into single equations related to single degree of freedom systems. It is the porpose of the paper to study the influence of the pounding on the response spectra and to evaluate the amplification due to the impact. For this purpose two adjacent SDOF systems are considered that are able to interact during the vibration process. This problem is solved versus the elastic stiffness ratio, which appears to be very important for such assemblage. The contact between masses is numerically simulated using opening gap elements as links. Comparisons between calculated response spectra and linear response spectra are made in order to derive analytical relationships to simply obtain the contribution of pounding. The results are graphically illustrated in response spectra format and the influence of the stiffness ratio is clarified.
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