Seismic up-grading of existing structures through the introduction of external dampers

CURADELLI, OSCAR; RIERA, JORGE; LETÍCIA FLECK FADEL MIGUEL

Geneva, Switzerland,

Conferencia; First European Conference on Earthquake Engineering and Seismology (a joint event of the 13th ECEE & 30th General Assembly of the ESC); 2006

The European Association of Earthquake Engineering (EAEE) and the European Seismological Commission (ESC)

Increasing awareness of seismic risk as well as new geological and seismological evidence, are leading to higher strength requirements in new buildings and structures throughout the world. Existing constructions, however, tend to remain as they are, i.e., nothing is legally required and very little is done. The consequence of this state of affairs is that in seismic regions of the globe, perhaps up to 80% of all existing buildings and structures are sub-standard, when their seismic reliability is compared with modern code requirements. In this paper the feasibility of up-grading the seismic strength or reliability of structures by introducing external dampers is examined, with emphasis in medium height concrete building structures and one or two-stories high masonry buildings. In the study, dampers similar to prototypes developed at the Laboratory of Structural Dynamics and Reliability (LDEC), UFRGS, Brazil were considered. The authors show that for purposes of seismic retrofitting of frame structures, external energy dissipation systems may be advantageously used. Through a full reliability analysis of typical low rise reinforced concrete frame buildings, it is demonstrated that the introduction of passive dampers results in a significant reduction of the probability of failure due to seismic excitation. In addition, the influence of external dampers on the seismic reliability of one or two-stories high masonry structures is examined using a similar approach. A substantial decrease of the probability of failure of the structures studied was verified. It is estimated that the seismic retrofitting may be achieved with costs of the order of 20% of the original cost of the structure.i.e., nothing is legally required and very little is done. The consequence of this state of affairs is that in seismic regions of the globe, perhaps up to 80% of all existing buildings and structures are sub-standard, when their seismic reliability is compared with modern code requirements. In this paper the feasibility of up-grading the seismic strength or reliability of structures by introducing external dampers is examined, with emphasis in medium height concrete building structures and one or two-stories high masonry buildings. In the study, dampers similar to prototypes developed at the Laboratory of Structural Dynamics and Reliability (LDEC), UFRGS, Brazil were considered. The authors show that for purposes of seismic retrofitting of frame structures, external energy dissipation systems may be advantageously used. Through a full reliability analysis of typical low rise reinforced concrete frame buildings, it is demonstrated that the introduction of passive dampers results in a significant reduction of the probability of failure due to seismic excitation. In addition, the influence of external dampers on the seismic reliability of one or two-stories high masonry structures is examined using a similar approach. A substantial decrease of the probability of failure of the structures studied was verified. It is estimated that the seismic retrofitting may be achieved with costs of the order of 20% of the original cost of the structure.