Elastic critical moments of I sections with very slender webs

Abstract

An analytical elastic distortional buckling theory is formulated in the chapter to investigate the elastic structural behavior of I-sections with very slender webs where cross section distortion in terms of local buckling of the web-plate and overall distortional buckling of the I- sections are fully incorporated. Through a standard eigen value analysis, the elastic critical moments of these sections are obtained, and comparison with finite strip results are also presented. Moreover, an extensive parametric study on I-sections with practical ranges of geometrical dimensions is also reported to assess the importance of distortional buckling for I-sections susceptible to lateral torsional buckling. Moreover, distortional buckling is found to be very significant in short to medium span beams with very slender webs, and specific design rules should be developed in assessing their structural behavior against distortional buckling. In this chapter, an eigen value analysis is established to assess the elastic critical moments of I-sections with very slender webs undergoing distortional buckling. Comparison on the elastic critical moments obtained from the proposed theory and the finite strip method is also presented in the chapter. Based on the results of an extensive parametric study, it is found that for I-sections with depth to web thickness ratios larger than 60, distortional buckling is apparent, especially in beams with short to medium spans. Consequently, distortional buckling should be allowed for in practical design of I-sections with very slender webs.