The research addresses the effect of diagonal and horizontal stiffeners on shear transfer in rigid frame square knees. Rigid frame square knees are an integral component of pre-manufactured metal building systems. This paper examined a more efficient design of the rigid frame square knee. Five full-scale laboratory tests on square knee joints were performed to verify the effects of a diagonal stiffener on shear transfer. Two frames were fabricated without diagonal stiffeners, and three frames were fabricated with 1/8- inch- thick diagonal stiffeners, not extending the full diagonal length of the knee web. Experimental results, coupled with a finite element analysis, are compared to AISC provisions in Section F4: shear yielding and shear buckling, and in Section G3: tension field action. This research shows that if diagonal stiffeners are needed, then thin, shortened diagonal stiffeners are sufficient to restrain shear buckling of the knee web until shear yielding occurs.

The analysis and optimum design of stiffened, shear webs in aircraft structures is addressed. The post-buckling behaviour of the webs is assessed using the interactive algorithm developed by Grisham. This method requires only linear finite element analyses, while convergence is typically achieved in as few as five iterations. The Grisham algorithm is extensively compared with empirical analysis methods previously used for aircraft structures and also with a refined, non-linear quasi-static finite element analysis. The Grisham algorithm provides for both compressive buckling in two directions as well as shear buckling, and overcomes some of the conservatism inherent in conventional methods of analysis. In addition, the method is notably less expensive than a complete non-linear finite element analysis, even though global collapse cannot be predicted. While verification of the analysis methodology is the main focus of the stud, an initial investigation into optimization is also made. In optimizing stiffened thin walled structures, the Grisham algorithm is combined with a genetic algorithm. Allowable stress constraints are accommodated using a simple penalty formulation. / Dissertation (MEng (Mechanical and Aeronautical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted