ABSTRACT
Numerical performance-based seismic design requires the use of reasonable tools to estimate structural damage. The maximum interstory drift and ductility demands have been targeted as performance parameters to achieve adequate damage control in earthquake - resistant structures. However, there is ample evidence that in some cases, the structural performance of structures subjected to long duration ground motions cannot be adequately characterized through its maximum deformation demands (Fajfar 1992, Cosenza & Manfredi 1996, Terán-Gilmore 1996, Fajfar & Krawinkler 1997, Rodríguez & Ariztizabal 1999, Huerta & Reinoso 2002, Bojórquez & Ruiz 2004, Arroyo & Ordaz 2007, Hancook & Boomer 2006, Terán-Gilmore & Jirsa 2007), in such manner that the effect of cumulative plastic deformations demands should be accounted explicitly during seismic design. The effect of the cumulative plastic deformation demands can be considered through the use of energy concepts; particularly through the use of the plastic hysteretic energy demand. The use of energy for this purpose was initially discussed
by Housner (1956), and has been used by several researchers to propose energy-based methodologies that aim at providing earthquake-resistant structures with an energy dissipating capacity that is larger or equal than their corresponding demands (Akiyama 1985, Akbas et al. 2001, Choi & Kim 2006, Bojórquez et al. 2008a). Due to the limitations of the maximum deformation as the principal indicator of structural damage, several damage indexes that include the use of plastic hysteretic energy have been formulated to better represent the consequences, in terms of structural damage and deterioration, of severe plastic cycling. Most research has been devoted to calibrate damage indexes for steel and reinforced concrete members (Krawinkler & Zohrei 1983, Park & Ang 1985, Bozorgnia & Bertero 2001, Teran & Jirsa 2005, Rodriguez & Padilla 2008). However, there is a challenge to study and calibrate the use of such indexes for the practical structural evaluation of multi-degree-of-freedom (MDOF) structures. For this reason, this paper proposes, for MDOF steel frames, an energy-based damage model that accounts explicitly for the effects of cumulative plastic deformation demands.
