Elasto-plastic buckling of curved web by the finite element method

Abstract

An elastic and elasto-plastic investigation of the buckling strength of the web of the curved plate girder is presented in this thesis. The results are expressed in the form of dimensionless design curves for proportioning the geometry of the curved panel.

Where possible, the results obtained herein are compared with existing predictlons. The results of the investigation are put into design recommendatios. These in turn are formulated in terms of design curves relating the various parameters involved in the design of curved web. Recommendations for further research are also included.

The finite element method of structural analysis was used to yield the eigenvalues of the stability problem. Computer programs based on iterative approach were developed to extract the critical stresses, both in the elastic and elasto-plastic cases.

For the first part of the investigation, the material of the web was assumed to be elastic. Due to high values of the critical stresses, an elasto-plastic buckling analysis of the web was also conducted for the case of pure circumferential stresses. For the plastic part, a method based on Hencky's deformation theory is developed with a new formulation of the secant modulus Eₛ.

Similar to the investigation done in straight plate girders, the web panel studied here is bound on the straight edges by stiffeners or diaphragms; and the extreme cases of edge loads considered are shear and pure circumferential stresses. The dimensions of the curved panel analyzed are well within the range of practical curved plate girders. Four types of boundary conditions were assumed; they are: --simple support on all edges --fixed support on all edges --fixed support along the curved edges and simply supported on the straight edges --fixed support on one curved edge and simply supported elsewhere.