M.Ing. (Mechanical Engineering) / This report describes an investigation into structural damping in simple steel structures. More specifictly, an attempt is made to obtain and compare the logarithmic decrement for different types of steel structures. The effect that welded and rivetted connections have on the logarithmic decrement is also examined. Four different types of steel are used, namely: mild steel and three types of chromium based steel. Vibration tests are performed on both cantiliver and simple bridge structures. An estimate of the inherent damping that is present in the vibrating structures are obtained from the approximate displacement-time response plots (as obtained from vibration tests). All the step input tests are modelled with a finite element. computer package to test the accuracy of the approximated response functions. Shaker tests are also performed on bridge structures. On the theoretical side the term damping is fully defined and discussed.

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by Dai Ruoli. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 85-88). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE - --- BACKGROUND AND LITERATURE REVIEW --- p.1 / Chapter 1.1 --- Piezoelectric Materials --- p.2 / Chapter 1.2 --- Literature Review on Vibration Control --- p.6 / Chapter 1.2.1 --- Passive control (PCL treatment) --- p.6 / Chapter 1.2.2 --- Active control (PA treatment) --- p.7 / Chapter 1.2.3 --- Active passive hybrid control (ACL and EACL treatment) --- p.8 / Chapter 1.3 --- Finite Element Method --- p.11 / Chapter 1.4 --- Positive Position Feedback Control --- p.12 / Chapter 1.5 --- Damping --- p.13 / Chapter 1.5.1 --- GHM method --- p.13 / Chapter 1.5.2 --- Rayleigh damping --- p.13 / Chapter 1.6 --- Thesis Objectives and Outline --- p.15 / Chapter CHAPTER TWO - --- SYSTEM MODELING --- p.16 / Chapter 2.1 --- Assumptions --- p.17 / Chapter 2.2 --- Elements --- p.18 / Chapter 2.3 --- FEM Matrices --- p.22 / Chapter 2.3.1 --- Element matrices component related to in-plane displacement --- p.22 / Chapter 2.3.2 --- Element matrices component related to bending displacement --- p.30 / Chapter 2.3.3 --- Element matrices component related to shear strain --- p.35 / Chapter 2.3.4 --- Overall element matrices --- p.38 / Chapter 2.3.5 --- Piezoelectric control forces --- p.39 / Chapter 2.4 --- Damping --- p.40 / Chapter 2.4.1 --- Damping due to the viscoelastic materials --- p.40 / Chapter 2.4.2 --- Inherent structural damping --- p.43 / Chapter 2.5 --- Edge Elements --- p.44 / Chapter 2.6 --- Model Reduction --- p.46 / Chapter CHAPTER THREE - M --- ODEL VALIDATION --- p.47 / Chapter 3.1 --- Beam with Passive ACL Damping Treatment --- p.48 / Chapter 3.2 --- Clamped-Clamped Plate with Fully Covered ACL --- p.50 / Chapter 3.3 --- Cantilever Plate with ACL/EACL Patch --- p.52 / Chapter CHAPTER FOUR - --- STUDIES ON EACL PATCH LOCATION --- p.57 / Chapter 4.1 --- Overview of the Numerical Examples --- p.58 / Chapter 4.2 --- Patch Location on Passive Damping Ability --- p.61 / Chapter 4.3 --- Patch Location on Actuating Ability --- p.65 / Chapter 4.4 --- Discussion on Patch Location --- p.69 / Chapter CHAPTER FIVE - --- SYSTEM IMPLEMENTATION --- p.71 / Chapter 5.1 --- Experimental Setup --- p.71 / Chapter 5.1.1 --- Open loop test --- p.72 / Chapter 5.1.2 --- Closed loop test --- p.72 / Chapter 5.2 --- Controller Design --- p.74 / Chapter 5.3 --- Results and Discussion --- p.76 / Chapter CHAPTER SIX - --- CONCLUSION AND FUTURE WORK --- p.81 / Chapter 6.1 --- Summary and Conclusion --- p.81 / Chapter 6.2 --- Recommendations for Future Research --- p.82 / "APPENDIX - PZT data sheet from PIEZO SYSTEMS, INC" --- p.83 / BIBLIOGRAPHY --- p.85

The objective of this study is to develop a nondestructive damage evaluation methodology that can identify simultaneously both stiffness and damping changes in a structure. Two approaches are used to meet the stated objectives. First, a method is developed on the basis of the conservation of total energy; second, the other method utilizes the acceleration-structural parameters (stiffness and damping) sensitivities. The total energy in a system consists of the sum of the kinetic energy, the potential energy, and the dissipated energy. In the second approach, a baseline structure is first identified. A baseline structure is defined to be a structural system having a similar dynamic response to the existing structure with no damage. In this study, natural frequencies and modal damping values are used to identify the baseline structure. The performance of the developed methodology is validated using several numerical experiments; Two classes of structures are considered here: (1) a high-rise building modeled as shear beams and (2) a two-span continuous beam structure. In the shear beam model of the structure, the damping damage is simulated by increasing the Newtonian dash pot constant which models the dissipation at the damaged story. For the two-span continuous beam structure, it is assumed that damping of the undamaged structure can be modeled using a proportional damping matrix. The damping matrix of the damaged structure is modeled as the combination of a proportional damping matrix of the undamaged structure and a stiffness proportional damping matrix of the damaged element. Three damage cases are investigated for each of the two structures considered here. Only one element experiences damping damage for the first damage scenario. In the second damage scenario, both stiffness damage and damping damage are simulated with different severities in one element of the model. In the third damage scenario, two elements are simulated with stiffness damage and damping damage, to verify whether or not the developed methodology works for multi-damage cases. The proposed method is modified to use mode shapes and the modified proposed method is applied to experimental data to identify stiffness damage in a R/C structure.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 96).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 116-118). Also available via the Internet.

Thesis (M.S.)--Miami University, Dept. of Physics, 2007. / Title from first page of PDF document. Includes bibliographical references (p. 52-53).

The work is focused in investigating the effectiveness of discretized damping tapes applied to a cantilever beam subjected to free and forced vibrations. The work is divided into three main sections. First, we performed material characterization of the viscoelastic (VE) pressure sensitive adhesive layer of the damping tapes. To do so, we designed a novel quad shear specimen to measure shear storage and loss moduli, and tan delta from dynamic mechanical analyzer measurements. Second, the optimal discretization length for different damping tapes was experimentally determined and analytically verified using linear viscoelasticity and basic strength of materials and vibrations principles. These results showed a mean to improve the damping of a structure without increasing the weight of the added damping layer. Third, a nonlinear analysis was performed for cantilever beams with damping layers subjected to parametric excitation. Comparison of the response amplitude of the parametrically excited beam was performed for different discretization lengths, and system identification of the nonlinear parameters was carried out. The effects of large deflections of a beam under parametric excitation were analyzed; large deflections were found to induce localized buckling of the stiff constraining layer of the damping tape that would invalidate some of the assumptions and analytical solutions that do not take such phenomena into account. / Master of Science

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