The ductility reduction factor in the seismic design of buildings

Abstract

SUMMARYThis paper presents new trends in the relationship between the ductility reduction factor and the ductility demand in the seismic design of buildings. A total of 4860 inelastic time-history analyses were carried out to study this relationship using 60 single-degree-of-freedom models excited by an ensemble of 81 earthquake accelerogram records from around the world. The asymmetrical distribution of the results highlighted the inaccuracies associated with assuming a normal distribution simply described by the mean and standard deviation to represent the data. A probability of exceedence approach has been used based on counting the number of occurrences the ductility demand exceeds a specified level. The ductility reduction factors developed in this study are consistent with other studies in the long-period range but are different in the short-period range. The ductility reduction factor for very short period buildings of limited ductility has been found to be greater than previously predicted.1998 John Wiley & Sons, Ltd.

Direct damage controlled seismic design of plane steel degrading frames

“…However, in both cases the accuracy is found to be satisfactory. Furthermore, it should be noted that examining the seismic analysis of structures, the scatter behavior of results is unavoidable; this has to do with the uncertainties associated with ground motions (Lam et al 1998, Hatzigeorgiou 2010). …”

The New Formulation of the Behavior Factor's “Theoretical -regulatory Aspect”

“…Priestley [12], a proposé une formulation du facteur de ductilité qui prend en compte la période caractéristique spécifique au site.…”

Building design based on energy dissipation: a critical assessment

“…The theoretical background of reduction factors suffers from shortcomings due to the fact the physical mechanisms involved are not rigorously defined Kappos (1999). For these reasons many researchers have tried to introduce new definitions for q and R factors, trying to take into consideration the uncertainties involved (Lu et al 2001;Miranda and Bertero 1994;Lam et al 1998). …”

“…Miranda and Bertero (1994) have found that strength reduction factors are primarily influenced by the maximum tolerable displacement ductility demand, the period of the structural system and the soil conditions of the site. Lam et al (1998) developed a relationship between the ductility reduction factor (R μ ) and the ductility for linear elasto-perfectly plastic SDOF systems (where R = R μ ) in order to rationalize seismic design provisions for codes of practices. Borzi and Elnashai (2000) employed an earthquake set to derive values for force reduction factors needed for the structure to reach, and not exceed, a pre-determined level of ductility.…”