Optimal prestressing and configuration of stayed columns (original) (raw)
2010, Proceedings of the Institution of Civil Engineers - Structures and Buildings
A steel column that is reinforced by prestressed stays generally has an increased strength in axial compression. In the past, greater emphasis was placed on obtaining its higher critical buckling load. However, detailed knowledge of the post-buckling behaviour is important to ensure the safety and the efficiency of the structure. Although previous work revealed that the optimal design should be determined with the post-buckling response, the actual values of the optimal prestress had not been previously evaluated. The present work examines the issue of the true optimal prestress for stayed columns through proposed structural optimisation indicators involving both instability and material quantity measures. Non-linear finite-element analysis was performed to investigate the non-linear buckling behaviour, which gives values for these indicators. Through a comparison of these values, suggestions for the configurations for improving the structural efficiency are presented.
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Buckling behaviour of prestressed steel stayed columns with imperfections and stress limitation
Engineering Structures, 2009
A steel column that is reinforced by prestressed stays, generally has an increased strength in axial compression. In the past, greater emphasis was placed on obtaining a higher critical buckling load. However, detailed knowledge of the post-buckling behaviour is important to ensure the safety and efficiency of the structure. The current work examines the buckling behaviour of a stayed column with geometrical imperfections, and stress limitation relating to possible material failure. A geometrically nonlinear model accounting for imperfect buckling behaviour of a stayed column was formulated using the Rayleigh–Ritz method, and then validated, using the finite element method. It is shown from these studies that the system tends to be most sensitive to imperfections at a prestress level that yields the highest critical load, and that the real maximum load capacity seems to increase as the prestress increases with a given configuration. The findings suggest that the optimal prestress should be greater than that found from using the previous convention that was based on linear analysis.
Post-buckling behaviour of prestressed steel stayed columns
Engineering Structures, 2008
A steel column that is reinforced by prestressed stays generally has an increased strength in axial compression. A geometrically nonlinear model accounting for the post-buckling behaviour of the stayed column is formulated using the Rayleigh–Ritz method and then validated using the finite element method. It is found that the post-buckling behaviour is strongly linked to the level of the initial prestress. As the prestress is increased, the following different levels of the responses can be observed in sequence: initial Euler buckling that subsequently restabilizes strongly, the critical load increasing with a post-buckling path that is either stable or unstable, an upper limit for the critical load where the post-buckling is unstable after an initially rather flat response. These findings are important for designers aiming to achieve safer and more efficient designs for this structural component.
INFLUENCE OF PRETWISTING ANGLE ON THE BUCKLING CAPACITY OF STEEL COLUMNS: A REVIEW
A column is a vertical compression member designed to transmit compressive loading. It is generally seen that when a slender member is loaded in compression, it will bow sideways or buckle, and if the load is then increased further the column will eventually fail in bending. Buckling is a mode of failure that is mainly observed in compression members due to structural instability. A pretwisted column has its strong flexural plane weakened and its weak flexural plane strengthened, leading to a favourable effect on buckling strength of the pretwisted column. A linear buckling analysis study was conducted for boxed and unboxed sections for columns with varying twist angles to study the effect of twist angle variation on improvement in buckling capacity. The studies reviewed that buckling capacity increased upto an optimum twist angle value and further reduced. It was found that pretwisting is effective to increase the buckling capacity of columns.
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