Numerical Studies on the Buckling Resistance of Prestressed Stayed Columns (original) (raw)

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.

Numerical studies of interactive buckling in prestressed steel stayed columns

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 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 a few studies into the postbuckling behaviour exist, interactive buckling behaviour has never been investigated. As interactive buckling can lead to more dangerous instabilities, the current work examines this for the most popular stayed column configuration using nonlinear finite element analysis. It is shown that interactive buckling becomes the worst case, with a commensurate decrease in the maximum load capacity, where a higher mode governs the critical buckling response.

Prestressed stayed beam-columns: Sensitivity to prestressing levels, pre-cambering and imperfections

Engineering Structures, 2021

The behaviour and structural performance of imperfect beam-columns with crossarms and externally prestressed cable stays are studied numerically, where the combination of bending and compression is assumed to be derived from the system self-weight acting orthogonally to the applied axial load. Both doubly-symmetric and mono-symmetric systems are studied. Sensitivity of the structural response to varying prestressing levels, pre-cambering and initial imperfections is investigated. Different initial imperfection levels and combinations are considered to facilitate the exploration of interactive buckling. The optimum prestressing force in terms of ultimate resistance and two structural efficiency indicators is also studied. It is found that relatively small crossarm lengths, stay diameters and crossarm length ratios should be avoided. Moreover, mono-symmetric cases are more sensitive to the level of pre-cambering than their doubly-symmetric counterparts. Considering both load-carrying capacity and structural efficiency, doubly-symmetric cases perform best with zero pre-cambering, but mono-symmetric cases perform best with upward precambering. As for the true optimum prestressing levels, these are recommended to be significantly above the linearly obtained optimum to maximize the structural efficiency.

Buckling mode interaction in prestressed stayed columns

Proceedings of the ICE - Structures and Buildings, 2013

Prestressed stayed columns offer an innovative and aesthetically attractive solution where designs demand long and slender elements under compression. The addition of cross-arms and pretensioned cables to the columns provide significant lateral and rotational support that can result in a marked increase of the buckling capacity. The current work presents a simplified model, comprising discrete rigidlinks and springs with a mathematically exact formulation including the destabilizing effect of cable slackening, which mimics the response of stayed columns and reveals the governing physical parameters that drive the behaviour. A recent finite element study had indicated that these structural components are likely to exhibit interactive buckling phenomena, particularly if the critical buckling mode is antisymmetric, leading to highly unstable responses. However, by its very nature, that study could not reveal the bifurcational structure of the equilibrium response. The results from the present model reveal similar behaviour to that observed in the earlier finite element study. A sequence of bifurcations is found that switch the post-buckling response from one mode to another via a path of interactive buckling. * Published in Proc. ICE Struct. Build., 166(SB8):403-412, 2013. R Ratio of rotational spring stiffnesses: c 0 /c S Shape of an eigenmode S i Labels of bifurcation points T Prestressing force in stays X Non-dimensional quantity:

Interactive buckling in prestressed stayed beam-columns

International Journal of Mechanical Sciences, 2020

The instability of beam-columns with crossarms and externally prestressed cable stays is studied analytically, where the combination of bending and compression is assumed to be derived from the system self-weight acting orthogonally to the applied axial load. A nonlinear analytical model for prestressed stayed beam-columns with doubly-symmetric and mono-symmetric configurations, based on the Rayleigh-Ritz method, is presented that captures modal interactions for perfect geometries explicitly for the first time. It is demonstrated that the theoretical compressive strength enhancements under certain configurations can only be obtained at the expense of triggering a sequence of destabilizing bifurcations. This can give rise to severely unstable interactive post-buckling behaviour including the so-called 'mode jumping' phenomenon. Moreover, for mono-symmetric stayed beam-columns, it is shown that the varying levels of prestress within the stays can lead to different buckling modes which all have their own characteristic post-buckling responses. The analytical model is verified using a nonlinear finite element model formulated within the commercial code ABAQUS and excellent comparisons are obtained.

Stability of Multiple-crossarm Prestressed Stayed Columns With Additional Stay Systems

Structures, 2017

Prestressed stayed columns have an enhanced resistance to buckling through the effective use of crossarms and pretensioned stays when compared to conventional columns. An analytical derivation of the minimum, linear optimum and maximum initial pretension forces for configurations of prestressed stayed columns with multiple crossarms and additional stays is presented for the first time. The findings are validated through comparisons with finite element models developed in the commercial package ABAQUS. The influence of the initial pretension on the load-carrying capacity of the configurations considered is also analysed, providing insight into the actual optimum initial pretension force for the configurations accounting for the significance of geometric nonlinearities.

Design of prestressed stayed columns

2013

General design procedures for prestressed stayed columns with a single cross-arm system are presented. The accuracy of the proposed design expressions is confirmed by comparison with the results of physical experiments and validated finite element simulations. Reliability is assessed by following the approach set out in Annex D of EN 1990. The presented resistance expressions for prestressed stayed columns are a function of the system geometry, the level of initial prestress in the cables and the global imperfection level. Worked examples are also presented to illustrate the application of the developed design approach.

Optimal prestressing and configuration of stayed columns

Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2010

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.

Optimal prestressing of triple-bay prestressed stayed columns

Structures, 2017

A nonlinear finite element model of a triple-bay prestressed stayed column is developed within the commercial package ABAQUS. A linearly obtained 'optimal prestressing force' that maximizes the critical buckling load is investigated since this quantity has been demonstrated in previous work on single-bay prestressed columns to provide a lower bound to the actual maximum load carrying capacity when compared to experimental results and nonlinear modelling. The ratio of the crossarm to the overall column length, the diameter of the cable stays, the relative lengths of the individual crossarms and the ratio of the initial prestressing force to the aforementioned linear optimal prestress are varied. Measures for the relative efficiency of the main column and the stays are defined and the objective of the optimization study is for the efficiency to be maximized. It is found that the true optimal prestress is generally higher than the equivalent, linearly obtained, quantity but by a significantly reduced factor when compared to an equivalent study for single-bay prestressed stayed columns.