Scale model technology represents one method of investigating the behavior of advanced, weight-efficient composite structures under a variety of loading conditions. Testing of scale models can provide a cost effective alternative to destructive testing of expensive composite prototypes and can be used to verify predictions obtained from finite element analyses. It is necessary, however, to understand the limitations involved in testing scale model structures before the technique can be fully utilized. The objective of this research is to characterize these limitations, or scaling effects, in the large deflection response and failure of composite beams. Scale model beams were loaded with an eccentric axial compressive load designed to produce large bending deflections and global failure. / Ph. D.

We present the concept of a frame and the related notion of spatiality. We consider the classical separation axioms in the frame setting and relate these to frame covering properties. Finally, a determination of which covering properties and separation axioms imply spatiality of a frame is made. / Master of Science

Non-ductile Reinforced Concrete Frames (RCF) with and without Unreinforced Masonry (URM) infills can be found in many places around the world including the Western United States, Eastern Europe, Asia and Latin America. These structures can have an unsatisfactory seismic performance which may even lead to collapse due to brittle failure modes. Furthermore, the effect of the infills on the seismic response of the structural system is not always accounted for in analysis and design. At present, there is no consensus on whether masonry infills are beneficial (by increasing the resistance of the system) or detrimental (by leading to brittle failure modes) for RCF construction. This study focuses on the development of a simplified modeling approach for non-ductile RCF with URMI that combines the simplicity of strut-and-tie models with the accuracy of Nonlinear Finite Element Analysis (NLFEA). Despite the fact that NLFEA procedures are the most advanced way to address the structural analysis of RCF with URM infills, their conceptual complexity and computational cost may hinder their widespread adoption as an analysis and design tool. At the same time, simplified methods, such as those based on the equivalent strut concept, may be overly crude and neglect essential aspects of the nonlinear response. To address the need for an adequately accurate, but computationally and conceptually efficient analysis method, this study establishes a novel method for planar RCF with URM infills subjected to lateral loads. The method, which is based on the Nonlinear Truss Analogy (NLTA) is shown to have an accuracy comparable to that of NLFEA. Specifically, the method is shown to adequately capture the strength and stiffness degradation and the damage patterns while entailing a reduced computational cost (compared to that of NLFEA). The proposed method is expected to bridge the gap between overly crude equivalent strut models and computationally expensive NLFEA. / Ph. D.

This study compares energy minimization with direct stiffness for linear structural analysis. The energy minimization approach locates the generalized displacement vector by minimizing the total potential energy of the structure being analyzed. From the survey of variable metric and conjugate gradient algorithms included in this study, the Davidon-Fletcher-Powell variable metric algorithm and the FletcherReeves conjugate gradient algorithm were chosen to minimize the total potential energy. A description of both algorithms is presented. The direct stiffness method assembles the equilibrium equations of the structure being analyzed. These equations are solved by Gaussian elimination to determine the generalized displacement vector. Computer codes have been written for the energy minimization and direct stiffness methods. The comparison was based on computational effort, in terms of computer time, required for analysis. The results of this study show energy minimization is not competitive with direct stiffness for linear structural analysis. As the problem size increases by degree of freedom the direct stiffness method rapidly increases in superiority over the energy minimization method. / Master of Science

A study was performed to develop an interactive plane frame analysis program. The program was designed to run on Unix-based workstations and to be independent of the hardware platform. This was achieved by selecting the XWindow system as the underlying graphical user-interface. An event-driven, window-based program was developed using the XWindow Toolkit. The entire program was written in the C programming language. The program consists of two parts: a preprocessor and a processor. The preprocessor employs pull-down menus and pop-up dialog boxes and provides a convenient way of creating and modifying structural models. The processor performs linear elastic analysis of plane frame structures based on the matrix displacement method. The processor computes joint displacements, support reactions and local member-end forces of the structure. It also handles internal hinges, joint loads, member loads, prescribed displacements, multiple load cases and load combinations. Other features include automatic mesh generation for orthogonal frames, automatic computation of self-weight and specification of output options. To verify the accuracy of the program, analysis results from the program were compared with results obtained from a commercial structural analysis program. A comparison of joint displacements, support reactions and member-end forces indicate that the difference in the values obtained from the two programs is less than two percent and that the program provides accurate analysis results. / Master of Science

Position and vibration control of a flexible beam is studied analytically and in the laboratory. Two different motor types are compared as actuators throughout the thesis: a standard voltage controlled motor and a torque controlled motor. The experimental beam is controlled with a dc-servo motor at its base and is instrumented with strain gages and a potentiometer. The control law is a form of linear, direct-output feedback. State estimators augment the control law to provide rate information that is not available from the instrumentation. Accurate modeling of the system’s inherent damping characteristics is achieved by analyzing experimental data. Gains were iterated yielding minimum-gain norm and minimum-sensitivity norm solutions to meet imposed eigenvalue placement constraints. Results for the two solutions and the two systems are compared and contrasted. Experimental verification of analytical results is hampered by unmodeled system non-linearities. Several attempts at bypassing these obstacles are shown. Finally, conclusions and recommendations are made. / Master of Science / incomplete_metadata

The objective of this study is to apply the combined linear buckling and nonlinear analysis to the stability investigations of the plane and space frame structures. A comparative study of the combined analysis and the nonlinear analysis is conducted with ABAQUS to demonstrate the applicability and effectiveness of the combined analysis for the critical load predictions. Several test problems and a glulam dome cap are analyzed, and the critical load prediction curves and the nonlinear equilibrium paths are presented. It is verified that the B33 finite element in ABAQUS is capable of modeling the curved beam. The modeling procedure of the dome cap model is discussed. Finally, conclusions and recommendations are made for future studies. / Master of Science

The current study explores the influence nontraditional framing of beauty and ugliness has on college aged females' interpretation of beauty. Focus group sessions were used to assess this influence, during which the women were asked several questions within two open discussions of beauty. The television sitcom Ugly Betty, which features an alternative framing of beauty standards, was shown between each discussion and used to analyze the media's influence. The results show that the discussion and the new framing of beauty and ugliness in the clip influenced the women's interpretations by either creating new understandings or re-enforcing existing beliefs. The women also considered media images of beauty to have a third-person effect with younger audiences being more impacted. Social comparison was used slightly in explaining beauty definitions and standards for women. / Master of Arts

Steel moment frames are a popular seismic-force resisting system, but it is believed that they are susceptible to early fracture if there is a stress concentration in the plastic hinge region, also known as the protected zone. If a defect is present in this area, it may be repaired by grinding and/or welding, but little research has investigated how the repairs affect the performance of full-scale moment connections subjected to inelastic rotations. Thus, the goals of this research were to establish the performance of full-scale moment connections with repairs and defects, then develop a method for predicting fracture of the full-scale specimens using more economical cyclic bend tests. To do this, six full-scale reduced beam section (RBS) connections were tested having arrays of repairs or defects applied to the flanges. The repairs were 0.125 in. deep notches ground to a smooth taper and 0.25 in. deep notches ground to a smooth taper, welded, and ground smooth. The defects were sharp 0.25 in. and 0.375 in. notches. In addition, 54 bend tests were conducted on beam flange and bar stock coupons having the same repairs and defects, power actuated fasteners, puddle welds, and no artifacts. Finally, Coffin-Manson low-cycle fatigue relationships were calibrated using results from the cyclic bend tests with each artifact (repair, defect, or attachment method) and used in conjunction with estimates of full-scale plastic strain amplitudes to predict fracture of full-scale specimens. All four of the full-scale moment connections with repairs satisfied special moment frame qualification criteria (SMF). One full-scale specimen with sharp 0.25 in. notches satisfied SMF qualification criteria, but the flexural resistance dropped rapidly after the qualification cycle. On the other hand, the specimen with sharp 0.375 in. notches did not satisfy SMF qualification criteria due to ductile fractures propagating from the notches. The proposed method for predicting fracture of full-scale connections was validated using the six current and six previous full-scale RBS specimens. This method underpredicted fracture for eleven of the twelve specimens. The ratio of the actual to predicted cumulative story drift at fracture had a mean of 1.13 and a standard deviation of 0.19. / M.S. / Moment connections in steel structures resist earthquake loads by permanently deforming the material near the connection. This area is called the protected zone and is critical to the safety of the structure in an earthquake. Due to this importance, no defects are allowed near the connection, which can include gouges or notches. If a defect does occur, it must repaired by a grinding or welding. These are the required repair methods, but there have be no tests to determine how the repairs affect the strength and ductility of the connection. This research tested six full-scale moment connections with defects repaired by grinding and welding, as well as unrepaired defects. A correlation was also developed and validated between the full-scale tests and small-scale bend tests of steel bars with the same defects and repairs. This relationship is valuable because the small-scale tests are quicker and less expensive to conduct than the full-scale tests, meaning other defects or repairs could be easily tested in the future. All but one of the six full-scale specimens met the strength requirements and had adequate ductility. The one test specimen that failed had an unrepaired defect. The relationship between the full-scale and small-scale tests underpredicted fracture (a conservative estimate) for the five of the full-scale tests and overpredicted fracture (unconservative estimate) for one test.

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