This thesis examines the use of diagonal tension (shear) testing to determine factors affecting shear strength of Interlocking Compressed Earth Block (ICEB) panels. This work expands on the current information available about strength properties of ICEB assemblies, which are dry-stacked, as opposed to having mortared beds. Variables such as block strength, grout strength and grouting pattern can influence the results of these types of tests and are examined in this investigation. To study variables affecting diagonal shear strength, 9 panels were tested, consisting of blocks produced by a manual block press. Strength testing was adopted from common ASTM standards to determine constituent material properties. A modified version of ASTM E519 test procedure is used to perform diagonal tension testing. Imaging analysis, using a high resolution camera, was run simultaneously during testing to capture displacement histories of select panels. It was determined that both block and grout strength significantly affect the shear strength of ICEB panels. Additionally, vertical grouting and block type also have a strong influence. Imaging analysis results confirm that the dominant failure mode in ICEB panels is bed joint sliding both pre and post peak load, with noticeable displacements at head joint locations on a few panels. Lastly, diagonal cracking along the block face was noticeable on several panels following peak load. Further testing remains to determine other factors affecting shear strength, namely, the application of normal pre-compression loads to the panel.

The study and design of light-weight automobiles has emerged as an important area of interest in the government, academia, and the manufacturing industry. Significant advances in vehicle weight reduction technologies have taken place in almost all fields of transportation. Weight reduction is identified as a key factor to achieving fuel-economy, energy efficiency and environmental safety. The main objective of this thesis is to investigate cost effective design methodologies that enable fabrication of light weight structures, which subsequently result in a fuel saving. A few important techniques and trends of weight reduction in the automotive industry over the past few years are studied as part of the thesis. A summary from the survey of various approaches to weight reduction is presented in the literature review. This thesis is based on the theory of semi-tension fields, which was originally applied towards the design of structures in the aircraft industry. A semi-tension field is a post buckling phenomenon in which the load is continued to be carried even after the web has buckled. The advantage of semi-tension fields is twoold: first, by using this theory the structural stability of the original structure is retained; and secondly, its application replaces a comparatively heavy-weight shear resistant web with a thin web, potentially resulting in reduced weight. The semi-tension field theory is applied to the redesign of back panel of a prototype Ford F-150 pick up truck, which was modeled and analyzed using IDEAS Master Series 8 FEA software. The literature review also consists of the survey of several advances in the Semi-tension fields theory, and the corresponding trends in weight reduction. Analytical theories related to semi-tension field-based design and the respective mathematical formulations have also been described. Finite element analyses of the design that resulted from the application of the theory were carried out and results were validated using analytical theories. A technical paper demonstrating the redesign of a door beam was also studied and results are presented as an appendix.

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

In design of an aircraft structure, the great emphasis is placed on achieving high weight efficiency. This thesis is focused on the stress analysis of the spars with thin web with or without web openings, which is one of the most important parts of the airplane structures. In comparison with traditional spars or beams, which are widely used in civil engineering applications, the design of the beam with thin web is more complicated. Thesis contains useful information for analytical calculation of this type of spars and its verification using finite element method and experimental measurement.

<p>A large rectangular industrial duct consists of plates stiffened with parallel wide flange sections. The plates along with stiffeners acts to resist the pressure loads and to carry other loads to the supports. The behaviours of the components of large industrial ducts are significantly different from the behaviours on which the current design methods are based on. Investigation presented herein deals with the design methods for spacing stiffeners, proportioning stiffeners and calculating shear resistance of side panel.</p> <p>Current method of spacing stiffeners is based on large deflection plate theory. A parametric study was conducted on dimensionless parameters identified in order to benefit from membrane action in partially yielding plate for spacing stiffeners. Design equations were established in terms of dimensionless pressure, plate slenderness and normalized out-of-plane deflection for three cases namely; 0%, 16.5% and 33% of through thickness yielding of the plate. Results show that approximately 50% increase in stiffener spacing when yielding of 16.5% of thickness is permitted.</p> <p>Under suction type pressure load, the unsupported compression flange and restrained tension flange lead to distortional buckling of the stiffeners. The current methods do not address distortional buckling adequately. A parametric study on dimensionless parameters governing the behaviour and strength of stiffened plat panels was conducted. The study indicated that the behaviour and strength of the stiffened panels could be a function of web slenderness and overall slenderness of the stiffener. The study also identified the slenderness limit of stiffener web for which the stiffener reaches the yield moment capacity. This study demonstrated the conservatism of current method. Finally a method was established to calculate the strength of stiffened plate panel subjected lateral pressure.</p> <p>Side panels adjacent to the supports transfer large amount of shear to the supports and, in addition, resist internal pressure. Currently the design of side panels for shear is based on the methods used for the web of fabricated plate girders. The behaviour and the characteristics between the web of plate girder and the thin side panels are significantly different. A parametric study was conducted on dimensionless parameters identified. It was concluded that the plate slenderness dominates the normalized shear strength of stockier side panels. The aspect ratio and plate slenderness influence the normalized shear strength of slender side panels. Design methods to calculate the shear strength of side panels were proposed.</p> / Doctor of Philosophy (PhD)