Calculation Method for Stable Ultimate Bearing Capacity of Irregular Space-shaped Bridge Pylon
The geometric configuration of irregular space-shaped bridge pylon(IS-SBP)is complex,which has the characteristics of irregular cross sections and non-ideal boundaries.It is difficult to obtain the stable ultimate bearing capacity(SUBC)by using the existing methods,and the safety of structure cannot be accurately perceived so that the material cost increases.Whereas the development of this kind of bridge pylon is rapid and with large numbers,the stability issues are prominent with the trend of towering structures,high strengthening materials and thin-walled components,and there is an urgent need to carry out study on the SUBC.The essence of the stability problem of bridge pylons is analyzed.By focusing on nonlinear stability safety factors and systematically considering the effects of component slenderness ratio,material nonlinearity,geometry nonlinearity and initial defects,the internal mapping relationship between stability safety factors and stability reduction factors is established,and the analysis method for the SUBC of IS-SBP is proposed.Then,the feasibility and accuracy of the proposed method are verified by comparing the SUBC results with the value from specifications by using the examples of typical ideal compression pylons,e.g.rectangular and circular reinforced concrete compression pylons,pure-steel box compression pylons,and concrete-filled steel box pylons.Finally,based on a typical IS-SBP cable-stayed bridge,a refined nonlinear finite element simulation strategy is constructed to obtain its SUBC.The result shows that the elastic stability safety factor of the structure is 18.56,the nonlinear stability safety factor is 4.125,and the stability reduction factor is 0.899.The SUBC is greatly reduced after considering the dual nonlinearity and initial defects,and the nonlinear stability safety factor is only 0.22 times of the elastic stability safety factor.For irregular space-shaped strut-pylon structure,the influence of nonlinearity on the SUBC of structure should be considered in design.
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