Budapest University of Technology and EconomicsFaculty of Civil Engineering - Since 1782

Lateral-torsional buckling (LTB) of beams is a classic problem in structural stability. The phenomenon is well-known for many decades. In the practice it appears most pronouncedly in thin-walled, e.g., steel beams. Various analytical and numerical solutions exist for the linear lateral-torsional buckling problem (i.e., when the structure and loading are assumed to be perfect, the material is linearly elastic, and nonlinearity of the strains is approximated by second-order relationships). There are various design methods, too, included in the relevant design standards for steel structures. It can be observed, however, that the solutions for the linear LTB problem are applicable under relatively specific circumstances only, while the solutions which can technically be applied for more general cases might significantly under- or overestimate the critical load values. As far as the design methods are concerned, they are not general enough, neither, moreover, the various design methods lead to diverse design resistances, with sometimes significant differences. (E.g., the current Eurocode 3 design code includes at least three different methods for LTB design.) One of the most important limitations of the available critical force formulae and design methods is that they can handle mostly doubly (or maybe singly) symmetrical cross-sections. The aim of the actual research is to investigate the lateral-torsional buckling of thin-walled beams with asymmetric cross-sections.

 

The proposed research covers both the linear LTB problem (i.e., calculation of critical load) and the prediction of the design resistance. In case of the linear problem it is planned to derive analytical solutions, as well as to apply/develop numerical procedures. In case of the design resistance nonlinear finite element simulations are to be performed with considering initial imperfections, as well as a few simple tests are planned to conduct.

 

The PhD applicant must have appropriate mechanical and mathematical background knowledge, as well as he/she must have high level ability to use non-linear finite element software (first of all: ANSYS). Fluency in English is a must, too. Programming skills and/or knowledge of a programming language (such as MatLab) is appreciated, as well as familiarity with current design standards for thin-walled steel is welcomed.