Demands and distribution of hysteretic energy in moment resistant self-centering steel frames

Post-tensioned (PT) steel moment resisting frames (MRFs) with semi-rigid connections (SRC) can be used to control the hysteretic energy demands and to reduce the maximum inter-story drift (<i>&#947;</i>). In this study the seismic behavior of steel MRFs with PT connections is estimated by incremental nonlinear dynamic analysis in terms of dissipated hysteretic energy (<i>E_H</i>) demands. For this aim, five PT steel MRFs are subjected to 30 long duration earthquake ground motions recorded on soft soil sites. To assess the energy dissipated in the frames with PT connections, a new expression is proposed for the hysteretic behavior of semi-rigid connections validated by experimental tests. The performance was estimated not only for the global <i>E_H</i> demands in the steel frames; but also for, the distribution and demands of hysteretic energy in beams, columns and connections considering several levels of deformation. The results show that <i>E_H</i> varies with <i>&#947;</i>, and that most of <i>E_H</i> is dissipated by the connections. It is observed in all the cases a log-normal distribution of <i>E_H</i> through the building height. The largest demand of <i>E_H</i> occurs between 0.25 and 0.5 of the height. Finally, an equation is proposed to calculate the distribution of <i>E_H</i> in terms of the normalized height of the stories (<i>h</i>/<i>H</i>) and the inter-story drift.