ASSESSMENT OF DISTRIBUTED NON-LINEAR FIBER MODELS

Abstract

The study evaluates existing numerical nonlinear modeling techniques used in seismic analysis. Experimentally tested RC bridge column specimens have been taken as a case study and modeled in Open Sees finite element software. The study shows that the distributed force-based (FB) fiber models provide a more accurate result in capturing the nonlinear behavior of the RC bridge column that exhibits strain-hardening behavior. In contrast, the distributed displacement-based (DB) fiber models overestimate the ultimate capacity of the RC bridge column for sections exhibiting strain-hardening behavior. The study shows that for nonlinear analysis using distributed displacement-based (DB) fiber models, members should be divided into several elements to capture the inelastic response accurately. For the section exhibiting strain-softening behavior, both the distributed force-based (FB) and displacement-based (DB) fiber models are affected by localization issues. To overcome the localization issues, three-level of regularizations have been compared: 1) Applying regularization only to concrete, 2) Applying regularization only to steel 3) Applying regularization to concrete and steel materials. The level of regularizations was observed to have a significant effect in capturing the softening behavior, such as concrete crushing/spalling or rupture of reinforcing steel bars.
Key words: beam-column fiber models, Nonlinear-analysis, Strain-Hardening, Strain-Softening, Localization, Regularization