| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 97 === Beam is one of the elements of structures which resists bending moment.
When steel beam is not supported properly by braces, lateral-torsional buckling may
become a major problem.
Therefore, finite element simulation is done to analyze the beam braced by
nodal torsional braces. Abaqus, one of the products of Simulia, is used to analyze the
beam. Two kinds of analyses is done. Those analyses are buckling analysis and load
versus displacement analysis. Buckling analysis is done because its first mode Eigen
value is used as initial imperfection shape in load versus displacement analysis.
H600 × 200 × 11 × 17, H592 × 350 × 16 × 36, and H792 × 350 × 19 × 36 beam
sections are studied. Each of them has different DT value which is a factor that
involves in lateral-torsional buckling. A continuous lateral brace is provided to
represent concrete slabs. Three kinds of lateral supports are used for each beam
section: (1) two nodal torsional braces, (2) a continuous lateral brace only on top
flange and two nodal torsional braces, and (3) a continuous lateral brace only on top
flange and two nodal lateral braces.
Based on the analysis results obtained, following conclusion can be drawn: (1)
following AISC specification about the unbraced length, Ls can be used to determine
the position of braces, (2) two percent rule can be used as an orientation in design, (3)
beams with high DT value are less susceptible to lateral-torsional buckling, (4) beam
with a continuous lateral brace only on top flange and nodal torsional braces has
higher plastic hinge rotation capacity than beam with a continuous lateral brace only
on top flange and nodal lateral braces, (5) beam without reduced section has 3% rad
plastic hinge rotation capacity higher than beam with reduced section (RBS) when
they are braced by nodal torsional braces, (6) a continuous lateral brace attached to
beam increases beam plastic hinge rotation capacity, and (7) the benefit of providing
beam with braces is 2% rad plastic hinge rotation higher than beam without braces.
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