• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.327-335
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• 2011

This study has two objectives: (1) to evaluate the degradation characteristics of symmetric unbraced steel frames by using analytical approach, and (2) to suggest equation which can approximately estimate the effect of degradation during the schematic design stage. For the analytical approach, the refined plastic hinge method with an arc length algorithm was adopted. The subject of analysis was one story one-bay, multistory one-bay, and multistory three-bay unbraced steel frames. The main parameters of the analytical approach include the stiffness ratio of column to beam and the axial force ratio. The study led to the following conclusions. The normalized stiffness of degradations is affected by both stiffness ratio of column to beam and the axial load ratio; however, the major influence on degradations is the axial force ratio. The equation, which can approximately estimate the effect of degradation, was suggested together with the research results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2A
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• pp.85-95
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• 2012

This paper presents an investigation on the ultimate behavior of steel cable-stayed bridges using nonlinear finite element analysis method. Cable-stayed bridges exhibit various geometric nonlinearities as well as material nonlinearities, so rational nonlinear finite element analysis should be performed for investigation of the ultimate behavior. In this study, ultimate behavior of steel cable-stayed bridges was studied using rational ultimate analysis method. Nonlinear equivalent truss element and nonlinear frame element were used for modeling the cable, girder and mast. Moreover, refined plastic hinge method was adopted for considering the material nonlinearity of steel members. In this study, the 2-step analysis method was used. Before live load analysis, initial shape analysis was performed in order to consider the dead load condition. For investigation of the ultimate behavior of steel cable-stayed bridges, analysis models which span length is 920.0 m were used. Radiating type and fan type were considered as the cable-arrangement types. With various quantitative evidences such as load-displacement curves, deformed shapes, locations of the yield point or region, bending moment distribution and so on, the ultimate behavior of steel cable-stayed bridges was investigated and described in this paper.