PERFORMANCE-BASED SEISMIC RESPONSE OF FRAME STRUCTURES INCLUDING RESIDUAL DEFORMATIONS. PART II: MULTI-DEGREE OF FREEDOM SYSTEMS

TLDR

Existing damage indices based on ductility or energy dissipation fail to capture residual deformations in frame structures. This study investigates residual deformations as a complementary indicator to cumulative damage in multi‑storey frame structures, extending the concept from single‑degree‑of‑freedom systems to multi‑degree‑of‑freedom systems. The authors analyze multi‑storey frame structures—both new and existing—by examining residual deformations, accounting for higher‑mode and P‑Δ effects, and defining global performance levels through a matrix of maximum and residual drift to support an alternative performance‑based design framework. Residual deformations are sensitive to hysteretic rule, inelastic mechanism, and seismic intensity.

Abstract

The role of residual deformations when evaluating the performance of multi-storey frame structures subjected to ground motion is investigated in this paper. The limitations of damage indices available in the literature, either based on ductility, energy dissipation or a combination of both, in capturing such a significant aspect of the seismic response of frame structures are discussed. The concept of residual deformations as a critical complementary indicator to cumulative damage, introduced in a companion paper (Part I) for single-degree-of-freedom (SDOF) systems, is herein extended to multi-degree-of-freedom (MDOF) frame systems. The seismic performance of multi-storey frame structures, either representative of new designed or existing structures, is investigated, focusing on the response in terms of residual deformations. Residual deformations are shown to be sensitive to the hysteretic rule adopted, to the system inelastic mechanism as well as to the seismic intensity. The influence of higher modes and P-Δ effects on the final residual deformations is addressed. A combination of maximum drift and residual drift in the format of a performance matrix is used to define the system's global performance levels and is then extended to a framework for an alternative performance-based seismic design and assessment approach.