Cyclic lateral-torsional buckling of short I-beams
Lee, Sang-Gab
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Permalink
https://hdl.handle.net/2142/21971
Description
Title
Cyclic lateral-torsional buckling of short I-beams
Author(s)
Lee, Sang-Gab
Issue Date
1990
Doctoral Committee Chair(s)
Hjelmstad, Keith D.
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
This report concerns the inelastic lateral buckling and post-buckling behavior of short I-beams subjected to cyclically reversing loads. The eccentrically braced frame, used in the earthquake resistant design of building structures, provides an application in which lateral buckling of short I-beams under cyclic loading is relevant. Our main purpose is to establish some benchmarks with which to assess the consequences of lateral buckling of active link beams in eccentrically braced frames.
A geometrically nonlinear beam model, capable of analyzing lateral buckling of short I-beams under cyclic loading, is formulated in terms of stress components. The novel kinematic model includes a geometrically exact representation of the primary torsional warping as well as secondary warping due to torsion and transverse shear. A new cyclic plasticity model, incorporating many of the most compelling features of existing phenomenological models, is developed and implemented with a consistent return mapping algorithm. The new model represents cyclic metal plasticity well and is suitable for large-scale computation.
The experimental research program comprised five tests of propped cantilever beams subjected to a cyclically reversing point load acting near the fixed end. The experiments include both braced and unbraced beams subjected to similar loading histories. The effects of constitutive parameters, residual stresses, load placement, geometric imperfections, flexible boundary conditions, and lateral bracing are examined using the analytical model developed herein. Most of the parameter studies are carried out using the propped cantilever arrangement used in the experiments.
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