Importance of Non-Simulated Failure Modes in Incremental Dynamic Analysis (Ida) of Non-Ductile RC Frames

Abstract eng:
Nonlinear dynamic analysis of reinforced concrete structures requires a thorough understanding of behavior of structural elements for all levels of performance, especially collapse. Main reason is that reinforced concrete is a mixed material having complicated nonlinear behavior, each element having several coupled degradation modes that influence the entire structure and can change its collapse mechanism. Therefore, using oversimplified models can lead to misleading results. This paper presents a numerical study on the relation among the non-simulated failure modes of the structural elements of non-ductile RC frames and their collapse mechanism; this study reports on the so-called “Structural resurrection” phenomenon in Incremental Dynamic Analysis (IDA). It consists in some structures collapsing under a certain accelerogram, although resisting the same accelerogram but scaled by a factor bigger than unity. This fact was reported, among other examples, in the Van Nuys Hotel; this work focusses on a RC frame of that building. Structural behavior is described with OpenSEES code accounting for flexural, shear and axial failure modes of structural members. Obtained results show that simplified models grossly overestimate the building capacity since several hidden failure modes are only detected by more complex formulations. The so-called structural resurrection might be merely due to the use of too simple models.

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