An elasticity solution is presented for the static equilibrium equations of an axisymmetric composite cylinder under loadings due to embedded piezoelectric laminae. The solution is used to study both uniform and non-uniform distributions of the piezoelectric effect and results are verified using the finite element method. A cylindrical truss element actuator is developed based upon this analysis and shown to be useful in damping vibrations of truss-type structures. It has also been shown that by varying the distribution of the piezoelectric effect. spatially, modal actuators capable of actuating specific modes of axial vibrations in a bar can be developed. Finally, the effects of a piezoelectric patch have been investigated. The axial forces generated at the fixed ends of a cylinder are demonstrated to be proportional to the length of the patch. / Master of Science

Cranes are an indispensable aid to the construction industry, and much responsibility with regard to performance has been placed in the hands of the operator. The problem of controlling sway of the load due to crane motion, or wind effects must be solved dynamically by the operator to increase productivity and maintain safety. At the hands of inexperienced operators safety is sometimes sacrificed in order to expedite the required task. In an effort to minimize the loss of life and equipment, and to maximize productivity a system for actively damping the crane load has been developed. This paper discusses an active damping system using state feedback control for a crane load modeled as a two-dimensional pendulum. Mathematical analysis indicates that the control theory used to damp the sway in the pendulum may be extended linearly into three dimensions. Thus, two control algorithms, operating independently, can be used to damp sway in two horizontal dimensions. The designed system responds to sensed displacements of the load from equilibrium. It employs a control arm positioned a small distance below the boom tip that applies a force to the cable to damp the sway of the load. This system is intended to allow less experienced operators to work more efficiently and safely, decreasing training time and increasing overall productivity. / Master of Science

Cranes, which comprise a significant class of material handling equipment, are basically designed to lift and lower loads. In addition to dynamic loading, cranes are exposed to loads which may be environment specific. Many crane accidents are due to uncontrolled swaying of the payload resulting in collisions with construction workers or objects. At present, it is left to the operator to apply his/her skills in controlling this uncontrolled swaying. If the controlling is automated and computer controlled, the effect of human errors and limitations can be minimized. The control of this sway will thus greatly improve safety and significantly enhance productivity. The control strategy in the present thesis is based on applying appropriate, periodic balancing forces and moments to the crane cable to dampen the oscillation. The present thesis presents a discussion on the experimental methods attempted before the development of an automated control. / Master of Science

In this study three types of optimized controllers are developed and tested on two laboratory structures. The two structures represented a progression in complexity and challenge to the controllers. The first structure was simple enough to be accurately modeled so the analytical frequencies and mode shapes agreed with the experimental measurements. The second structure being more complex was more difficult to model so differences between the analytical results and experimental measurements were present. These differences required the application a correction method to the reduced models developed for the second structure. The correction method was shown to work with good results on one reduced model and with poor results on the second reduced model. Two direct rate feedback control laws and a linear quadratic regulator with state estimation (LQG controller) were designed and implemented on both structures. It was shown that the performance of the LQG controller can be approached with a much simpler direct rate feedback controller with better analytical-experimental agreement. The best analytical-experimental agreement occurred with the simplest controller applied analytically to the corrected reduced model demonstrating the validity of the correction method as well as giving a strong reason to use simpler controller designs. / Ph. D.

A series of resonant column and torsional shear (RCTS) and large scale resonant column (LSRC) tests were performed to investigate the dynamic properties (shear modulus and material damping ratio) of municipal solid waste (MSW). the MSW materials were recovered from the Tri-Cities landfill adjacent to the San Francisco Bay in California. A total of 30 specimens 2.8-in. (71.1-mm) and 6.0-in. (152.4-mm) of old, fresh, and mixed MSW were reconstituted in accordance with established sample preparation procedures. Ten of specimens were small-diameter (2.8-in. (71.1-mm)) RCTS specimen and 20 specimens were larger (6.0-in. (152.4-mm)) LSRC specimens. Dynamic laboratory measurements were performed in the linear and nonlinear strain ranges. Test parameters affecting the dynamic properties in the linear range included: (1) duration of confinement, (2) isotropic total confining pressure, [sigma]o, (3) excitation frequency, f, and (4) specimen size. Other test parameters affecting dynamic properties in the nonlinear strain range were: (1) shearing strain amplitude, [gamma], (2) isotropic total confining pressure, (3) overconsolidation ratio, (4) number of loading cycles, and (5) excitation frequency. In addition, the effects on dynamic properties of MSW specimens of material parameters such as (1) waste composition, (2) water content, (3) unit weight of waste, and (4) particle size were evaluated. The total unit weights of old, fresh, and mixed MSW specimens were estimated during testing in the RCTS and LSRC devices. These estimated total unit weights in the laboratory were compared with those measured at other MSW landfills and were found to generally be less than the field measurements. At a given [sigma]o, Gmax decreases with decreasing weight percentage of soil-size (passing the 3/4-in. (19.1-mm) sieve) material. However, Dmin increases slightly with decreasing weight percentage of soil-size material. Another relationship was developed between estimated total unit weight, [gamma]t, and confining pressure, including weigh percentage of soil-size material. The Vs profiles of old, fresh, and mixed MSW specimens obtained in the laboratory tests were compared with those measured at other MSW landfills in situ. The 62 to 76% soil-size material groups are in good agreement with in-situ Vs profiles. The variation in normalized shear modulus and material damping ratio curves were patterned after the Darendeli model (2001) for different weight percentages of soilsize material. An empirical relationship between normalized shear modulus (G/Gmax) and modified material damping ratio (D-Dmin) was developed in the nonlinear strain range. As part of collaborative research project, nonlinear shear modulus reduction and material damping curves generated by The University of Texas at Austin (UT) and The University of California at Berkeley (UCB) were compared according to different weight percentages of soil-size material. Furthermore, nonlinear shear modulus reduction and material damping ratio curves generated by UT were also compared with ones previously proposed by other researchers.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Robert Bradlee Campbell. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 65. / by Mark Howard Sloan. / B.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 60. / by Susan Russell Stapleton. / B.S.

Abstract not available

A global, multi-level, wave-mean flow model based on an approximate version of the primitive equations is developed to investigate the development of a baroclinic wave field initially confined to a single zonal wavenumber. The effects of physical processes (surface drag and thermal damping) and internal diffusion on the evolution have been examined. The nature of the mean flow adjustment by the nonlinear baroclinic waves is also studied. For a simulation with a relatively strong internal diffusion it is found that a single life cycle characterized by baroclinic growth and barotropic decay is obtained (as in Simmons and Hoskins, 1978), whereas with weaker diffusion the wave undergoes secondary life cycles before a nearly wave-free state is reached (as in Barnes and Young, 1991). In an experiment with weak 4th order diffusion secondary life cycles occur with little net decay. Relatively strong barotropic growth follows the initial life cycle. In experiments with surface drag (Rayleigh friction) and thermal damping (Newtonian cooling), repeated life cycles of baroclinic growth and barotropic decay can be obtained. It is found that in the complete absence of surface drag, the flow evolves to a nearly wave-free state after one secondary cycle. This demonstrates that surface drag plays an important role in nonlinear baroclinic instability. With relatively strong surface drag multiple life cycle behavior is found for sufficiently strong thermal damping. Such a behavior strengthens for very strong thermal damping. A steady wave state in which the wave amplitude equilibrates at an essentially constant level has only been obtained with very strong "potential vorticity damping". Both the "barotropic governor" process (James and Gray, 1986) and the baroclinic adjusment process are responsible for major parts of the stabilization of the mean flow in simulations with and without surface drag and thermal damping. However, the "barotropic governor" process dominates the flow evolution in the model simulations without surface drag and thermal damping. The "barotropic governor" modifies the meridional gradient of zonal mean potential vorticity, which influences the baroclinic adjustment. / Graduation date: 1992