COMITÊ BRASILEIRO DE BARRAGENS – CBDB
PRELIMINARY EARTHQUAKE DESIGN SPECTRUMS IN BRAZIL AND
APPLICATIONS TO STRESS FIELD EVALUATION IN CONCRETE GRAVITY
DAMS
Paulo Marcelo Vieira RIBEIRO
Doctorate Student – University of Brasília
pauloribeiro@unb.br
Lineu José PEDROSO
Professor – University of Brasília
lineu@unb.br
George SAND
Professor – University of Brasilia Seismological Observatory – OBSIS
georgesand@unb.br
ABSTRACT
Although still present in the popular imagination, the idea that the Brazilian territory is
devoid of earthquakes and tradition that structures designed in this region does not
require special considerations on this phenomenon are losing strength. Standards for
the seismic design of structures were recently developed and reports of seismic
phenomena in the country are not rare. The Brazilian seismic activity is low but not
non-existent. Earthquakes of significant magnitudes have been recorded and seismic
history of this region is still little known.
Greater understandings of seismology, the availability of new records of earthquakes
and seismic observations of the behavior of structures have shown that a strong
earthquake could induce a significant dynamic amplification, capable of possible
structural damage in concrete dams. The evaluation of seismic safety of dams is a
growing concern, because accidents involving this type of structure have catastrophic
consequences, with human and material losses.
This study aims at the construction of design spectrums from seismic records
obtained at various sites on the national territory, where significant earthquakes were
recorded. Later, from a spectral acceleration corresponding to the desired
earthquake the seismic actions are calculated and applied in a typical profile of
Brazilian dam, in an equivalent static analysis, with the objective of verifying the
changes in stress distribution along the structure due to earthquake action.
Calculations are performed using the Pseudo-Dynamic Method (used for preliminary
seismic design of concrete gravity dams), which considers the structural flexibility and
fluid compressibility.