Linear and Nonlinear Buckling Response and Imperfection Sensitivity of Cable-Stayed Masts and Pylons

摘要

An approximate analytical method for quantifying the lateral resistance offered by inclined cables to guyed towers, such as the pylons of cable-stayed bridges, is presented first. For this purpose, an analytical expression was derived for the evaluation of the pylon's effective buckling length. Taking into account the cables' inclination and prestressing and approximating the nonlinearity caused by sag using Dischinger's formula, the cables were substituted by horizontal translational springs of equivalent stiffness. Then, an analytical solution of the linear buckling load of the equivalent spring model was obtained. The presented analytical method can be very useful at the preliminary design stage. Then, the approximate results were compared to the ones extracted from geometrically nonlinear finite element analysis with imperfections (GNIA) of both the more exact cable-pylon model and the spring-pylon model. The results show that the critical buckling load is predicted with very good accuracy for a wide range of values of cable inclination and pre-tensioning and indicate an unstable post-buckling behavior. In- and out-of-plane buckling of pylons with single or multiple levels of cables, in either a fan or a harp arrangement, with either a fixed or a hinged base, is addressed. A parametric analysis showed a strong imperfection sensitivity leading to significantly smaller ultimate loads of the imperfect structures compared to the linear buckling loads.