A study was conducted to understand how the smoothness of the skeleton curve before a structure yield affects its seismic response. The bulging of the skeleton curve was represented using the ratio of initial stiffness in a bilinear model, followed by numerous nonlinear dynamic analyses. The results showed that for ductility µ = 1, the ratio of the required demand yield seismic coefficient drops below 1 when the structure's natural period Teq is short, reducing seismic response values. Applying these insights to seismic response calculations is expected to improve accuracy, particularly in assessing structures around yielding, such as during Level 1 earthquakes or post-earthquake evaluations.
