The assessment of Reinforced Concrete (RC) buildings, considering mainshock-aftershock (MA)
sequences, has been addressed in previous studies in which the main objective is to predict the damage
level after a maximum expected aftershock and then judge if the building can continue operating or not.
This study uses numerical simulations to determine the equivalent damping ratio for structures with low
energy dissipation and under mainshock-aftershock sequences and using several Single Degree of
Freedom (SDOF) systems with different hysteresis models.
Results indicate the variation of the damping ratio for each hysteresis model, and the higher
and lower values correspond to the Degrading trilinear and Origin-oriented models, respectively. In
addition, the parameter 𝑎2, which is defined as the ratio of the yielding stiffness to the elastic stiffness
of the capacity curve, presents a significant influence on the equivalent damping ratio. For that reason,
in the beginning, this study presented a new expression to determine the damping ratio, which considered
new reduction factor values “𝛾” and a new coefficient to quantify the additional damping ratio due to
the damage before yielding point “𝑏,” both were determined for specific values of the parameter 𝑎2.
Due to the high values and the uncertainty of coefficient “𝑏,” the new expression was reduced
for practical purposes during the mainshock and aftershock. Additionally, the damage level (ductility)
for the maximum expected aftershock, and using the new “𝛾” values, presented a lower error percentage
than the previous studies, which considered 𝛾 equal to 0.06.
Keywords:
RC buildings, damping ratio, mainshock, aftershock.