Chapter 10 - Effects of Viscous Damping Models, Hysteretic Models and Ground Motion Characteristics on Seismic P-Delta Strength Amplification Factors

Abstract

This chapter presents the results of an extensive series of analyses that were performed on single-degree-of freedom (SDOF) systems to better understand the effects of the viscous damping model, the hysteretic model, the frequency content of the earthquake ground motions, and the structural period of vibration on P-delta strength amplification factors. Parametric studies have been performed to examine the influence of the viscous damping modeling, the hysteretic behavior and the characteristics of ground motions on the seismic P-delta strength amplification factor for single-degree-of-freedom systems with various structural periods. For elastic-perfectly plastic systems, similar amount of strength amplification is required to compensate for P-delta effects regardless of whether the damping coefficient is proportional to the initial stiffness or the tangent stiffness of the system. However, viscous damping models that are proportional to the tangent stiffness of the system are influenced by the amount of strain hardening present. If the stability coefficient exceeds the strain hardening ratio, energy is fed into the structure by the damping mechanisms when yielding occurs. Judgment must be exercised while using these models.