While moment frames are a popular lateral-force resisting system, their constant cross-section can lead to inefficiencies in energy absorption and stiffness. By tapering the flange width linearly toward the center of the beam length, the energy absorption efficiency can be increased, leading to a better elastic response from the beam and more elastic stiffness per pound of steel used. Lateral-torsional buckling is an important failure mode to be considered for tapered-flange moment frame shapes. No closed-form or finite element solutions have yet been developed for tapered-flange I-beams with a non-uniform, linear moment gradient and intermediate bracing conditions. In this study, finite element analysis is used to find the buckling stress of each W-shape in the AISC Steel Construction Manual with both a standard straight-flange and the proposed tapered-flange at several lengths and with three intermediate lateral bracing conditions (no bracing, mid-span bracing, and third-span bracing). Plots are generated for each shape at each bracing condition as the buckling stress versus length for both beams and columns. Overall, the results indicate that lateral-torsional buckling of tapered-flange I-beams is not a problem that would prohibit the wide-scale use of this configuration in moment frames. Also, the buckling capacity tapered-flange moment frame shapes can be reasonably estimated as 20% of the corresponding straight-flange moment frame shape.

We investigate the implementation of nontraditional open-loop and closed-loop control techniques to systems at the micro and macro scales. At the macro level, we consider a quay-side container crane. It is known that the United States relies on ocean transportation for 95% of cargo tonnage that moves in and out of the country. Each year over six million loaded marine containers enter U.S. ports. Current growth predictions indicate that container cargo will quadruple in the next twenty years. To cope with this rapid growth, we develop a novel open-loop input-shaping control technique to mitigate payload oscillations on quay-side container cranes. The proposed approach is suitable for automated crane operations, does not require any alterations to the existing crane structure, uses the maximum crane capabilities, and is based on an accurate two-dimensional four-bar-mechanism model of a container crane. The shaped commands are based on a nonlinear approximation of the two-dimensional model frequency and, unlike traditional input-shaping techniques, our approach can account for large hoisting operations. For operator-in-the-loop crane operations, we develop a closed-loop nonlinear delayed-position feedback controller. Key features of this controller are that it: does not require major modifications to the existing crane structure, accounts for motion inversion delays, rejects external disturbances, and is superimposed on the crane operator commands. To validate the controllers, we construct a 1:10 scale model of a 65-ton quay-side container crane. The facility consists of a 7-meter track, 3.5-meter hoisting cables, a trolley, a traverse motor, two hoisting motors, and a 50-pound payload. Using this setup, we demonstrated the effectiveness of the controllers in mitigating payload oscillations in both of the open-loop and closed-loop modes of operation. At the micro level, we consider a micro optical device known as the torsional micromirror. This device has a tremendous number of industrial and consumer market applications including optical switching, light scanning, digital displays, etc. To analyze this device, we develop a comprehensive model of an electrically actuated torsional mirror. Using a Galerkin expansion, we develop a reduced-order model of the mirror and verify it against experimental data. We investigate the accuracy of representing the mirror using a two-degrees-of-freedom lumped-mass model. We conclude that, under normal operating conditions, the statics and dynamics of the mirror can be accurately represented by the simplified lumped-mass system. We utilize the lumped-mass model to study and analyze the nonlinear dynamics of torsional micromirrors subjected to combined DC and resonant AC excitations. The analysis is aimed at enhancing the performance of micromirrors used for scanning applications by providing better insight into the effects of system parameters on the microscanner's optimal design and performance. Examining the characteristics of the mirror response, we found that, for a certain DC voltage range, a two-to-one internal resonance might be activated between the first two modes. Due to this internal resonance, the mirror exhibits complex dynamic behavior. This behavior results in undesirable vibrations that can be detrimental to the scanner performance. Torsional micromirrors are currently being implemented to provide all-optical switching in fiber optic networks. Traditional switching techniques are based on converting the optical signal into electrical signal and back into optical signal before it can be switched into another fiber. This reduces the rate of data transfer substantially. To realize fast all-optical switching, we enhance the transient dynamic characteristics and performance of torsional micromirrors by developing a novel technique for preshaping the voltage commands applied to activate the mirror. This new approach is the first to effectively account for inherent nonlinearities, damping effects, and the energy of the significant higher modes. Using this technique, we are able to realize very fast switching operations with minimal settling time and almost zero overshoot. / Ph. D.

No / Closed-form expressions are derived for the torsional stiffness, radial stiffness and tilting stiffness of annular rubber flanged bushes of finite length in three principal modes of deformation, based upon the classical theory of elasticity. Illustrative numerical results are deduced with realistic physical data of typical flanged bushes.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24228号 / 工博第5056号 / 新制||工||1789(附属図書館) / 京都大学大学院工学研究科マイクロエンジニアリング専攻 / (主査)教授 土屋 智由, 教授 平方 寛之, 教授 江利口 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Corrugated web plate girders (CWPGs) have become an increasingly popular structural member in Canada in recent years. This is because of their economic efficiency over standard wide flange members. Although the flexural performance of such has been increasingly studied in recent years there is still advancements that can be made in their design. No research has been completed in Canada on the subject of lateral torsional buckling (LTB) strength and very minimal research has been published on sinusoidal CWPGs. In order to examine the LTB strength of a CWPG with a sinusoidally shaped web, nine specimens were loaded and failed in simply supported arrangement that favours lateral torsional buckling. Specimens were chosen to observe the difference in strength due to web thickness, web depth and variation in identical beams. All of the specimens recorded strengths that exceeded the theoretical design strengths confirming that the current design procedure is conservative. A trend of ultimate capacity increasing was observed with the increase of web thickness. The depth of the web had no significant effect on the torsional strength besides what is gained from the increased flange distance. An equivalent web thickness equation was formulated based on the results for the purpose of calculating LTB strength. To test the proposed equation a numerical analysis was run on a wider range of beams and compared with the testing results. It was determined the physical testing results can be effectively captured by the proposed equation among more than just the tested beams. Two additional analyses were prepared to lay the foundation for further investigation of the proposed equation. The first was a Monte Carlo simulation to test the risk of using the proposed equation which requires additional data. Secondly, a preliminary finite element analysis (FEA) model was developed and presented for future use to expand this research. / Thesis / Master of Applied Science (MASc) / Corrugated web plate girders (CWPG) have grown in popularity due to their economic efficiency. No research has been presented in Canada and very minimal research has been published on the lateral torsional strength of CWPGs with sinusoidally corrugated webs. This research studied the lateral torsional buckling (LTB) strength of CWPGs through the experimental testing of physical members and a new equation for the calculation of the LTB strength is proposed. This equation and design process was then numerically tested to determine its viability as a design process.

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The research summarized the experimental analysis and finite element modeling of the lateral and rotational response of unbraced wood composite I-joists to worker loads. All experimentation and modeling was conducted on simply supported I-joists varying from 11-7/8 inches to 14 inches in depth and 20 feet to 24 feet in length. I-joists were subjected to static and dynamic loads. The deflections of the top and bottom flanges, as well as the rotation, were measured or calculated at both one-half and one-quarter the span length. The overall goal of this project is to accurately model the lateral and rotational displacements caused by human load effects. I-joists were first tested statically by subjecting each joist to a three point bending test, free from all lateral restraints. This test was necessary to prove that the performance of the joists was repeatable. Lateral and rotational stiffness of the joist were calculated at one-half and one-quarter of the span length. The static experimental tests results were statistically analyzed using an analysis of variance (ANOVA) test. The results from this analysis indicated no difference between repetitions of the same joist; however, the test did indicate that there was a significant difference between joists of the same manufacture and size. Dynamic testing was then conducted. Dynamic loads were induced by having test subjects traverse each I-joist. The resulting loads induced at the top and bottom flanges were recorded for use in the finite element model. The lateral deflections and induced loads were compared to the static weight of the test subject and analyzed with an ANOVA test. The results indicated an increase in both the induced load and resulting deflection with an increase in weight. The analysis also indicated an increase in load and deflection with a decrease in lateral and rotational joist stiffness. The recorded load values from the dynamic test were used as inputs into a finite element model. The resulting lateral deflections of the midpoint and quarter point were generated. The rotation of the beam was calculated from the difference between the top and bottom flange. Experimental results and finite element model results were compared by calculating a running average of the error between the acquired data and the finite element model. The model was said to be valid until the average model error reached 10 percent of the maximum acquired test value. All six deflection readings were analyzed in this manner. The percent of beam at which the model no long represented the test data was determined for each data set. This point was averaged across all deflection readings of similar joists and across all data sets of the same joist type. The model predicted the 20 foot long 11-7/8 and 14 inch deep joists until 54.5 percent and 51.2 percent, respectively, of the beam completed by the test subject. However, the 24 foot long 11-7/8 inch deep joist was only accurate to 31.2 percent of the beam completed by the test subject. Differences in peak values, and the time at which the peak values occurred were also analyzed using an ANOVA test. There was a significant difference between the peak values of the acquired test data and the deflections generated with the finite element model. However, there was no significance within the time that the peak values occurred between the model and experimental results. A simplified pseudo dynamic analysis was conducted using a constant percentage of the test subject's static weight applied to the top and bottom flange. This approximation proved adequate for the lateral displacement and rotation of the 11-7/8 inch and 14 inch deep and 20 foot long I-joists. However, the model became un-conservative for the 11-7/8 inch deep and 24 foot I-joists. / Master of Science