Practical Recommendations from ATC-62 for Capturing Post-Elastic Behavior of Components and Systems

摘要

This paper is a follow-up to a presentation last year (Heintz 2007) on the results of numerical studies of degrading systems as a part of the ATC 62 project. The project document is nearly complete and includes detailed recommendations for practical application up by engineers. These include clarification of the post elastic behavior of structural components (i.e. a force-displacement capacity boundary in place of "backbones"). When the properties of components are represented realistically, the resulting force displacement (pushover) curve for the structural model defines an important boundary that can be used to estimate the post elastic behavior. Current procedures (FEMA 356/ASCE41) require that this boundary reflect a minimum strength (R_(max)) to avoid dynamic instability. An improved procedure for determining this limit is presented. If the limit is not met, a nonlinear dynamic analysis is required. For many structures a simplified nonlinear procedure, using a SDOF model based on the pushover curve, can be subjected to incremental dynamic analysis to determine the probability of instability and other limit states. These procedures also show promise for adaptation to MDOF models. The presentation will focus on examples of applications to actual buildings.