Accounting for hysteretic characteristics in P‐delta analysis of structures

Abstract

Studies in the literature have shown that P‐delta () effects are highly influenced by the hysteretic characteristics of a structural system. However, international buildings and bridge codes prescribe ‐induced amplification factors, limits for negligible effects and limits for dynamic instability that neglect this influence. As a result, different margins of safety against actions are currently specified for different structural systems, with steel structures, for example, presenting reduced margins of safety with respect to concrete structures. Adopting a sub‐set of the PEER earthquake record database composed of 1964 earthquake records, this paper presents a statistical analysis of displacement amplification ratios for systems with different hysteretic models, fundamental periods and ductility levels. In terms of both elastic and inelastic stability coefficients, limit values of the stability coefficient for negligible effects and dynamic instability are proposed for the most common structural typologies, such as steel, well and poorly detailed reinforced concrete, and self‐centering structures. Analytical estimates of the median, 84th and 98th percentile values of the displacement amplification that take into account the combined effect of stability coefficient, ductility level and hysteretic properties are proposed.