How is the short-period spectral response adjusted in seismic design?

The adjustment of the short-period spectral response in seismic design involves applying a site factor, often referred to as Fa, to the short period spectral acceleration, Ss. This process is essential because the seismic response of structures can vary significantly based on site-specific conditions such as soil type, geological features, and local seismicity.

By applying the site factor Fa to the short period spectral acceleration, engineers can account for these variations, ensuring that the design adequately reflects the potential seismic forces that the structure may experience in its actual site conditions. This adjustment is a critical step in the design process, as it helps in establishing safe and reliable parameters for building structures that may be subjected to seismic activity.

Other options focus on different aspects of seismic analysis. While multiplying by S1 pertains to the long-period spectral response, calculating fundamental frequency is related to the natural characteristics of the structure rather than directly adjusting the spectral response. Determining the damping ratio is important for understanding energy dissipation, but it does not directly adjust the short-period spectral response in the context of seismic design. Thus, applying the site factor Fa to Ss is the correct and most relevant approach in this context.