Optimized slender and short-thick beams are used in building, aircraft and machine structures to increase performance at a lower material cost. A previous work proposes an optimum shape, material and size selection model to design lightweight slender beams under pure bending. In short-thick beams, the transverse shear effects are no longer negligible and impact the choice of the optimum shape. This work extends such an optimum selection model to consider both slender and short-thick beams, by formulating the total beam stiffness design requirement as a combination of shear and bending stiffness. Selection charts are developed to show the impact of design variables, such as shape, size, material and slenderness, on the total beam stiffness. The model of total beam stiffness is validated against computational results from finite element analyses of beam models. A case study demonstrates the use of the selection charts to compare the performance of beams at the conceptual design stage.

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Modal analysis is the experimental characterization of the dynanlical behavior of a structure. Recent advances in laser velocimetery have made available to the experimentalist a rich, new source of vibration data. Data can now be obtained from many different spatial locations on a structure. A method is presented to use this new data for the analysis of beams. Two approaches are investigated: minimum residual methods and boundary condition methods. The minimum residual approaches include autoregressive methods and non-linear least squares techniques. Significant contributions to sample rate considerations for parametric sinusoidal estimation resulted from this research. The minimum residual methods provide a good connection between the measured data and the fitted model. However, they do not yield a true modal decomposition of the spatial data. The boundary condition approach provides a complete modal model that is based on the spatial data and is completely compatible with classical beam theory. All theoretical constraints are included in the procedure. Monte Carlo investigations describe the statistical characteristics of the methods. Experiments using beams validate the methods presented. Advantages and limitations of each approach are discussed. / Ph. D.

A generalized solution technique has been designed and developed for the static and dynamic analysis of induced strain actuated beam structures. A PC-based, user-friendly, menu-driven software program DAISA (Dynamic Analysis of Induced Strain Actuated Beams) has been developed for the analysis of structural response due to induced strain actuation, with a highly user-friendly interface. Transfer matrices have been used to generalize the beam problem to accommodate different boundary conditions, loading conditions due to an arbitrary number of symmetric actuator patches on the beam structure, structural damping effects, and the effects of stiffening and mass loading due to the presence of the actuators. DAISA has been designed to perform static-response, free-vibration, steady-state harmonic-response, and frequency-response analyses describing the structural response to induced strain actuation. Various modeling techniques, including the Static, equivalent thermal expansion, and impedance approaches have been incorporated. DAISA has also been equipped to perform an electro-mechanical analysis of the beam-actuator system thereby providing adequate information about power consumption and system power requirements. The algorithm and software presented in this thesis will serve to achieve better design considerations for actuators employed in structural and vibration control. / Master of Science

A number of older bridges built before the 1970’s were constructed with floor systems consisting of a non-composite concrete slab over steel girders. Many of these bridges do not satisfy current load requirements and may require replacement or strengthening. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders to permit the development of composite action. This dissertation describes a research program investigating methods to develop composite action in existing non-composite floor systems by the use of postinstalled shear connectors. Three types of post-installed shear connection methods were investigated. These methods are referred to as the double-nut bolt, the high tension friction grip bolt, and the adhesive anchor. These post-installed shear connectors were tested under static and fatigue loading, and design equations for ultimate strength and fatigue strength were developed. These post-installed shear connectors showed significantly higher fatigue strength than conventional welded shear studs widely used for new construction. The superior fatigue strength of these post-installed shear connectors enables strengthening of existing bridge girders using partial composite design, thereby requiring significantly fewer shear connectors than possible with conventional welded shear studs. Five full-scale non-composite beams were constructed and four of these were retrofitted with post-installed shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30-percent shear connection ratio. A non-composite beam was also tested as a baseline specimen. Test results of the full-scale composite beams showed that the strength and stiffness of existing non-composite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero moment regions to reduce slip at the steel-concrete interface. Parametric studies using the finite element program ABAQUS were also conducted to investigate the effects of beam depth, span length, and shear connection ratio on the system behavior of strengthened partially composite beams. The studies showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders constructed using post-installed shear connectors. / text