Capacity-demand index relationships for performance-based seismic design

Seismic design approaches in current U.S. building provisions advocate using several static and dynamic analysis procedures. Among the static procedures, it is common to use linear and nonlinear methods that depend on capacity-demand index relationships (e.g., the relationship between the design lateral strength and the maximum lateral displacement). The benefit of using these relationships comes from their simplicity and adaptability, however significant deficiencies exist in their development.; Foremost, previous research on the development of capacity-demand index relationships is based on linear-elastic single-degree-of-freedom acceleration response spectra, whereas current design procedures are based on “smooth” design response spectra. For the design procedures to be consistent, new relationships need to be developed using smooth design response spectra.; Furthermore, previous research on capacity-demand index relationships is limited to the maximum displacement ductility demand. However, other demand indices such as to quantify cumulative damage and residual displacement are needed for use in the framework of a performance-based design approach that allows the designer to specify and predict the performance of a building under an earthquake.; Finally, using nonlinear dynamic analysis procedures as part of a performance-based design approach has become increasingly common. These procedures are often conducted using ground motions scaled to constant peak ground motion characteristics (e.g., peak acceleration) resulting in a large scatter in the analysis results. Ground motions should be scaled based on methods that adequately define the damage potential for given site conditions and structural characteristics, thus resulting in consistent prediction of the demand estimates by minimizing the scatter.; This dissertation proposes new capacity-demand index relationships and ground motion scaling methods and shows that: (1) previous capacity-demand index relationships developed using linear-elastic ground motion spectra can lead to unconservative designs, particularly for survival-level, soft soil, and near-field conditions; (2) the correlation between the maximum displacement ductility demand and other demand indices is relatively strong; and (3) scaling methods that work well for ground motions recorded on stiff soil and far-field conditions lose their effectiveness for soft soil and near-field conditions.