Inelastic buckling of torsionally braced I-girders under uniform bending: I. Numerical parametric studies

Inelastic buckling of torsionally braced I-girders under uniform bending, II: Experimental study

“…The AASHTO LRFD [2] strength curve also showed a good correlation with the analysis results when the lateral-torsional buckling deformations scaled by the ratio of two thousandth (2/1000) to each unbraced length L b was only associated for the initial imperfection model. The design strength curves of the Eurocode 3 [3] were excellently matched with the converged analysis results, especially when the imperfection factor α LT was considered as a low level (=0.34) [1]. When the lateral-torsional deformation model [4] and the ECCS residual stress model [5] were jointly adopted for the initial imperfection, the analytically evaluated strengths turned out to be considerably lower than the strength curves from the AASHTO LRFD specifications [2] and the Eurocode 3 [3].…”

“…Meanwhile, according to the previous study [1], it was found that the sectional moment of inertia required for the crossbeams of the multi-girder system should be approximately 1%-2% of the main I-girder to form a brace point against the lateral-torsional buckling. The moment of inertia of the transverse web stiffeners required to prevent web distortion at the crossbeam locations could be much different from the design provisions for shear buckling resistance of webs.…”

“…As indicated in the companion paper [1], these days steel Igirder bridges braced by torsional bracings like the diaphragm type crossbeam have been favorably utilized for structural efficiency. Through the numerical parametric studies [1] conducted by using the incremental nonlinear analysis, it was observed that the analytically evaluated strength values could be considerably varied with the initial imperfection models.…”

“…Through the numerical parametric studies [1] conducted by using the incremental nonlinear analysis, it was observed that the analytically evaluated strength values could be considerably varied with the initial imperfection models. The AASHTO LRFD [2] strength curve also showed a good correlation with the analysis results when the lateral-torsional buckling deformations scaled by the ratio of two thousandth (2/1000) to each unbraced length L b was only associated for the initial imperfection model.…”

“…The moment of inertia of the transverse web stiffeners required to prevent web distortion at the crossbeam locations could be much different from the design provisions for shear buckling resistance of webs. Also, it can be seen in the companion paper [1] that the design criteria regarding the torsional bracings in the AISC design specifications [6] tend to excessively demand the distortional stiffness for the transverse web stiffeners. For a design example, it was revealed that the AISC design criteria would require 14 times larger stiffness than the analysis results for the transverse web stiffeners.…”