Plate Shear Buckling: Mechanics and Enhancements Using Low-Frequency Sinusoids

Abstract

Slender steel plates are very common in various applications ranging from buildings to bridges to ships to aircraft. These slender plates are susceptible to plate shear buckling, though they have significant additional strength after buckling that is utilized in design. However, the mechanics of this postbuckling shear strength is still not fully understood; traditional theories such as Tension Field Action are used in design codes and posit that the source of postbuckling shear strength is a band of diagonal tension known as the tension field, which anchors onto the stiffeners like the posts of a Pratt truss. However, fundamental assumptions of these theories were proven to be untrue in recent research, prompting a reevaluation of the mechanics and a search for a stronger mechanics basis for design codes. The objective of this research is to elucidate the fundamental mechanics of web shear buckling and to propose economical and practical design strategies that improve shear performance, such that the design of slender plates can be optimized.The research results can be grouped into three major outcomes. First, web compression stresses are mobilized after elastic shear buckling at the two ends of the tension field, forming two compression fields that equilibrate the tension field in place of the transverse stiffeners and flanges. Second, horizontal anchoring onto adjacent web panels can increase postbuckling shear strength, though it is not necessary for the development of postbuckling shear strength. Third, a practical design strategy known as low-frequency sinusoids (LFS) is proposed to enhance slender plate shear buckling strength without welded transverse stiffeners or cross frames. The strategy forms low-frequency sinusoids with wavelength on the order of 1 meter along a web plate’s longitudinal axis. The contributions from this Ph.D. dissertation can benefit both the stability research community and practicing engineers, fabricators, and contractors. Both theoretical mechanics and practical design strategies are offered to optimize the design and performance of slender plates.