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Letteratura scientifica selezionata sul tema "Damping (Mechanics)"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 26 luglio 2024

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Articoli di riviste sul tema "Damping (Mechanics)"

1

Barone, P. M. V. B., e A. O. Caldeira. "Quantum mechanics of radiation damping". Physical Review A 43, n. 1 (1 gennaio 1991): 57–63. http://dx.doi.org/10.1103/physreva.43.57.

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2

Saravanos, D. A. "Integrated Damping Mechanics for Thick Composite Laminates and Plates". Journal of Applied Mechanics 61, n. 2 (1 giugno 1994): 375–83. http://dx.doi.org/10.1115/1.2901454.

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A method for predicting the damped dynamic characteristics of thick composite laminates and plates is presented. Unified damping mechanics relate the damping of composite plates to constituent properties, fiber volume ratio, fiber orientation, laminate configuration, plate geometry, temperature, and moisture. Discrete layer damping mechanics for thick laminates, entailing piecewise continuous displacement fields and including the effects of interlaminar shear damping, are described. A semi-analytical method for predicting the modal damping and natural frequencies of thick simply-supported specialty composite plates is included. Applications demonstrate the validity, merit, and ranges of applicability of the new theory. The applications further illustrate the significance of interlaminar shear damping, and investigate the effects of lamination, thickness aspect ratio, fiber content, and temperature.

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3

Shen, I. Y. "Hybrid Damping Through Intelligent Constrained Layer Treatments". Journal of Vibration and Acoustics 116, n. 3 (1 luglio 1994): 341–49. http://dx.doi.org/10.1115/1.2930434.

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This paper is to propose a viable hybrid damping design that integrates active and passive dampings through intelligent constrained layer (ICL) treatments. This design consists of a viscoelastic shear layer sandwiched between a piezoelectric constraining cover sheet and the structure to be damped. According to measured vibration response of the structure, a feedback controller regulates axial deformation of the piezoelectric layer to perform active vibration control. In the meantime, the viscoelastic shear layer provides additional passive damping. The active damping component of this design will produce adjustable and significant damping. The passive damping component of this design will increase gain and phase margins, eliminate spillover, reduce power consumption, improve robustness and reliability of the system, and reduce vibration response at high frequency ranges where active damping is difficult to implement. To model the dynamics of ICL, an eighth-order matrix differential equation governing bending and axial vibrations of an elastic beam with the ICL treatment is derived. The observability, controllability, and stability of ICL are discussed qualitatively for several beam structures. ICL may render the system uncontrollable or unobservable or both depending on the boundary conditions of the system. Finally, two examples are illustrated in this paper. The first example illustrates how an ICL damping treatment, which consists of an idealized, distributed sensor and a proportional-plus-derivative feedback controller, can reduce bending vibration of a semi-infinite elastic beam subjected to harmonic excitations. The second example is to apply an ICL damping treatment to a cantilever beam subjected to combined axial and bending vibrations. Numerical results show that ICL will produce significant damping.

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4

Qin, Yan, Shi Wei Zhao, Bi Fang Dai, Qi Lin Mei e Zhi Xiong Huang. "Studies on Properties of Epoxy Resin Base Piezoelectricity Damping Carbon Fiber Composite Materials". Key Engineering Materials 508 (marzo 2012): 271–75. http://dx.doi.org/10.4028/www.scientific.net/kem.508.271.

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Damping Materials Have Been Wildly Used in Aerospace, Traffic, Construction Fields and so on. The Piezo-Damping Materials Have Received much Attention due to the Novel Energy Loss Mechanism. In this Paper, Piezo-Damping Composite Materials Were Prepared from the Epoxy Resin (EP) as the Resin Matrix, Nano Lead Titanate (Nano-PT) Ceramics as Piezoelectric Material and Chopped Carbon Fibers (CF) as Conductive Materials. The Mechanical and Damping Properties of the Composites Were Analyzed by Mechanics Test, DMA and Vibration Beam Method. The Results Showed that when the Nano-PT Content Was 60% of EP and CF Content Was 0.25% of EP, the Composite Got the Better Mechanical Properties. Form DMA, the Loss Factor (tanδ) Peak Reached 0.58. Damping Temperature Range △T (tanδ>0.3) Was about 36.3°C. In Comparison, Damping Loss Factor Measured by Vibration Beam Method Was 0.82.

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van KAMPEN, N. G. "DAMPING AND NOISE IN QUANTUM MECHANICS". Fluctuation and Noise Letters 01, n. 02 (giugno 2001): C7—C13. http://dx.doi.org/10.1142/s0219477501000299.

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In a quantum system damping and noise enter through the coupling with an external large bath. The usual treatments computes the density matrix of the system by expanding in the coupling strength to the bath and averaging over the bath. The result, however, is known to be unacceptable as it leads to negative probabilities. It is here proposed to study correlation functions rather than the density matrix itself. Equations for them are derived and compared with the result obtained by the usual method.

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6

Buchmüller, W., e A. Jakovác. "Classical statistical mechanics and Landau damping". Physics Letters B 407, n. 1 (agosto 1997): 39–44. http://dx.doi.org/10.1016/s0370-2693(97)00746-6.

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7

Kausel, Eduardo. "Damping Matrices Revisited". Journal of Engineering Mechanics 140, n. 8 (agosto 2014): 04014055. http://dx.doi.org/10.1061/(asce)em.1943-7889.0000770.

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8

Heo, B., H. Bittner, M. L. Shumway e I. Y. Shen. "Identifying Damping of a Gyroscopic System Through the Half-Power Method and Its Applications to Rotating Disk/Spindle Systems". Journal of Vibration and Acoustics 121, n. 1 (1 gennaio 1999): 70–77. http://dx.doi.org/10.1115/1.2893950.

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This paper applies the half-power method to identify damping of a gyroscopic system. At first, the underlying principle of the half-power method for damped, gyroscopic systems is explained. Then the method is demonstrated on a rotating disk/spindle system often used in computer hard disk drives. The disk/spindle system consists of multiple elastic disks mounted on a rigid spindle supported by ball bearings. The flexibility of the bearings allows the spindle to undergo rigid-body translation and rocking. Calibrated experiments were conducted in vacuum to obtain frequency response functions at different rotational speed. Application of the half-power method shows that the disk and bearing dampings are independent of rotational speed and can be modeled adequately as viscous damping. Moreover, the damping of the ball bearings is two orders of magnitude smaller than that of a fluid-film bearing of similar size.

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Saravanos, D. A., e J. M. Pereira. "Dynamic Characteristics of Specialty Composite Structures with Embedded Damping Layers". Journal of Vibration and Acoustics 117, n. 1 (1 gennaio 1995): 62–69. http://dx.doi.org/10.1115/1.2873868.

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Damping mechanics for predicting the damped dynamic characteristics in specialty composite structures with compliant interlaminar damping layers are presented. Finite-element based mechanics incorporating a discrete layer (or layer-wise) laminate damping theory are utilized to represent general laminate configurations in terms of lay-up and fiber orientation angles, cross-sectional thickness, shape and boundary conditions. Evaluations of the method with exact solutions and experimental data illustrate its accuracy. Additional parametric studies demonstrate the unique capability of angle-ply composite laminates with cocured interlaminar damping layers to significantly enhance structural damping.

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10

ADHIKARI, S., e J. WOODHOUSE. "IDENTIFICATION OF DAMPING: PART 1, VISCOUS DAMPING". Journal of Sound and Vibration 243, n. 1 (maggio 2001): 43–61. http://dx.doi.org/10.1006/jsvi.2000.3391.

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Più fonti

Tesi sul tema "Damping (Mechanics)"

1

Ting-Kong, Christopher. "Design of an adaptive dynamic vibration absorber". Title page, contents and abstract only, 1998. http://thesis.library.adelaide.edu.au/adt-SUA/public/adt-SUA20010220.212153.

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Ehnes, Charles W. "Damping in stiffener welded structures". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FEhnes.pdf.

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3

Messalti, Mansour. "Viscoelastic damping of beams /". Online version of thesis, 1988. http://hdl.handle.net/1850/10414.

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4

Alberts, Thomas Edward. "Augmenting the control of a flexible manipulator with passive mechanical damping". Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/19442.

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5

Oosting, Kenneth W. "Simulation of control strategies for a two degree-of-freedom lightweight flexible robotic arm". Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/18230.

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Hsu, Yi-Chu. "Damping treatments for microstructures /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/7054.

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West, Ray A. "Damping of elastic-viscoelastic beams /". Online version of thesis, 1992. http://hdl.handle.net/1850/11111.

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Spang, Alan Wesley Jr. "In situ measurements of damping ratio using surface waves". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19590.

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9

Schultze, John Francis. "Evaluation of analytical and experimental methods to predict constrained layer damping behavior". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09122009-040317/.

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Graves, Kynan E., e kgraves@swin edu au. "Electromagnetic energy regenerative vibration damping". Swinburne University of Technology, 2000. http://adt.lib.swin.edu.au./public/adt-VSWT20060307.120939.

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This thesis documents a PhD level research program, undertaken at the Industrial Institute Swinburne, Swinburne University of Technology between the years of 1997 and 2000. The research program investigated electromagnetic energy regenerative vibration damping; the process of recovering energy from damped, vibrating systems. More specifically, the main research objective was to determine the performance of regenerative damping for the application of vehicle suspension systems. This question emerged due to the need for continuous improvement of vehicle efficiency and the potential benefits possible from the development of regenerative vehicle suspension. It was noted, at the outset of this research, that previous authors had undertaken research on particular aspects of regenerative damping systems. However in this research, the objective was to undertake a broader investigation which would serve to provide a deeper understanding of the key factors. The evaluation of regenerative vibration damping performance was achieved by developing a structured research methodology that began with analysing the overall requirements of regenerative damping and, based on these requirements, investigated several important design aspects of the system. The specific design aspects included an investigation of electromagnetic machines for use as regenerative damping devices. This analysis concentrated on determining the most promising electromagnetic device construction based on its damping and regeneration properties. The investigation then proceeded to develop an 'impedance-matching' regenerative interface, in order to control the energy flows in the system. This form of device had not been previously developed for electromagnetic vibration damping, and provided a significant advantage in maximising energy regeneration while maintaining damping control. The results from this analysis, when combined with the issues of integrating such a system in vehicle suspension, were then used to estimate the overall performance of regenerative damping for vehicle suspension systems. The methodology and findings in this research program provided a number of contributing elements to the field, and provided an insight into the development of regenerative vehicle systems. The findings revealed that electromagnetic regenerative vibration damping may be feasible for applications such as electric vehicles in which energy efficiency is a primary concern, and may have other applications in similar vibrating systems.

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Più fonti

Libri sul tema "Damping (Mechanics)"

1

G, Jones David I., e Henderson John P. 1934-, a cura di. Vibration damping. New York: Wiley, 1985.

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2

T, Sun C. Vibration damping of structural elements. Englewood Cliffs, N.J: Prentice Hall PTR, 1995.

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3

D, Johnson Conor, American Society of Mechanical Engineers., Society of Photo-optical Instrumentation Engineers. e U.S. Air Force Wright Laboratory., a cura di. Smart structures and materials, 1996.: 26-27 February 1996, San Diego, California. Bellingham, Wash., USA: SPIE, 1996.

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4

Córdova, Carlos Juán Cornejo. Elastodynamics with hysteretic damping. Delft, Netherlands: DUP Science, 2002.

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5

T, Sun C. Vibration damping of structural elements. Englewood Cliffs, N.J: PTR Prentice Hall, 1995.

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6

Banks, H. Thomas. On damping mechanisms in beams. [Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1989.

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7

Chen, Goong. Vibration and damping in distributed systems. Boca Raton, FL: CRC Press, 1993.

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8

1946-, Kinra Vikram K., e Wolfenden Alan 1940-, a cura di. M³D: Mechanics and mechanisms of material damping. Philadelphia: ASTM, 1992.

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9

Rivin, Eugene I. Stiffness and damping in mechanical design. New York: Marcel Dekker, 1999.

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10

Dew, Dwight D. Strain dependent damping characteristics of a high damping manganese-copper alloy. Monterey, Calif: Naval Postgraduate School, 1986.

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Capitoli di libri sul tema "Damping (Mechanics)"

1

Strømmen, Einar N. "Damping". In Springer Series in Solid and Structural Mechanics, 355–408. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-01802-7_9.

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2

Teidelt, Elena, Valentin L. Popov e Markus Heß. "Frictional Damping". In Method of Dimensionality Reduction in Contact Mechanics and Friction, 189–95. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-53876-6_12.

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3

Morino, Luigi. "Damping and Aerodynamic Drag". In Mathematics and Mechanics - The Interplay, 545–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2021. http://dx.doi.org/10.1007/978-3-662-63207-9_14.

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4

Panza, M. J., F. J. Sah, R. W. Mayne e D. J. Inman. "Prospects of Damping Structures via Actuator Interaction". In Computational Mechanics ’88, 1263–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-61381-4_336.

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5

Al-Rifaie, Hasan, e Wojciech Sumelka. "Auxetic Damping Systems for Blast Vulnerable Structures". In Handbook of Damage Mechanics, 1–23. New York, NY: Springer New York, 2020. http://dx.doi.org/10.1007/978-1-4614-8968-9_71-1.

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Al-Rifaie, Hasan, e Wojciech Sumelka. "Auxetic Damping Systems for Blast Vulnerable Structures". In Handbook of Damage Mechanics, 353–75. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-60242-0_71.

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7

Hattori, Toshio. "The Mechanisms and Mechanics Analyses of Fretting Wear and Fretting Fatigue". In Fretting Wear, Fretting Fatigue and Damping of Structures, 71–175. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-46498-0_3.

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Johnson, Erik A., e Baris Erkus. "Structural Vibration Mitigation Using Dissipative Smart Damping Devices". In Solid Mechanics and Its Applications, 227–36. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0179-3_19.

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Wedig, Walter V. "Random Vibrations of Riding Cars with Bilinear Damping". In Solid Mechanics and Its Applications, 387–99. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0179-3_34.

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Goyder, Hugh G. D. "Damping Due to Joints in Built-Up Structures". In The Mechanics of Jointed Structures, 135–47. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56818-8_11.

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Atti di convegni sul tema "Damping (Mechanics)"

1

"DAMPING OF DISK BODIES VIBRATIONS". In Engineering Mechanics 2019. Institute of Thermomechanics of the Czech Academy of Sciences, Prague, 2019. http://dx.doi.org/10.21495/71-0-303.

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2

Radolf, V., J. Horáček, V. Bula, A. Geneid e A.-M. Laukkanen. "Damping of human vocal folds vibration". In Engineering Mechanics 2022. Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Prague, 2022. http://dx.doi.org/10.21495/51-2-321.

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3

Úradníček, J., M. Musil, M. Bachratý e F. Havelka. "DESTABILIZATION OF DISC BRAKE MECHANICAL SYSTEM DUE TO NONPROPORTIONAL DAMPING". In Engineering Mechanics 2020. Institute of Thermomechanics of the Czech Academy of Sciences, Prague, 2020. http://dx.doi.org/10.21495/5896-3-496.

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4

Danberg, James, e Paul Weinacht. "Approximate Computation of Pitch-Damping Coefficients". In AIAA Atmospheric Flight Mechanics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-5048.

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Weinacht, Paul, e James Danberg. "Evaluation of Sacks' Pitch-Damping Relationships". In AIAA Atmospheric Flight Mechanics Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-5467.

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Wanderley, Juan B. V., Andre´ Ramiro, Thiago Reis, Antonio Carlos Fernandes e Carlos Levi. "Numerical Simulation of Roll Damping". In 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92166.

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The highly viscous flow problem of roll damping of a FPSO is investigated by means of numerical solution of the unsteady two-dimensional Navier-Stokes equations. The finite volume method using non-structured grid is used to solve the integral form of the governing equations. The cross section of the FPSO hull with an initial roll displacement is let free to oscillate in roll in an initially still fluid. The numerical simulation provides a realistic picture of the physics of the phenomenon, capturing the vortex formation around the bilge keel. Numerical results from roll free decay tests are compared with experimental data showing a fairly good qualitative and quantitative agreement of the roll damping.

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"Non-linear damping in the system of two-axis gyroscopic stabilizer". In Engineering Mechanics 2018. Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, 2018. http://dx.doi.org/10.21495/91-8-765.

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Danowsky, Brian P., Peter Thompson, Dong-Chan Lee e Martin J. Brenner. "Modal Isolation and Damping for Adaptive Aeroservoelastic Suppression". In AIAA Atmospheric Flight Mechanics (AFM) Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-4743.

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Hroncová, D., I. Delyová e P. Sivák. "DETERMINATION OF THE RELATIONSHIP BETWEEN KINEMATIC QUANTITIES OF A MECHANICAL SYSTEM WITH DAMPING". In Engineering Mechanics 2020. Institute of Thermomechanics of the Czech Academy of Sciences, Prague, 2020. http://dx.doi.org/10.21495/5896-3-206.

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Ryabov, Victor, e Boris Yartsev. "Coupled damping vibrations of anisotropic box beams". In 2015 International Conference on Mechanics-Seventh Polyakhov's Reading. IEEE, 2015. http://dx.doi.org/10.1109/polyakhov.2015.7106769.

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Rapporti di organizzazioni sul tema "Damping (Mechanics)"

1

Minz, Dror, Eric Nelson e Yitzhak Hadar. Ecology of seed-colonizing microbial communities: influence of soil and plant factors and implications for rhizosphere microbiology. United States Department of Agriculture, luglio 2008. http://dx.doi.org/10.32747/2008.7587728.bard.

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Original objectives: Our initial project objectives were to 1) Determine and compare the composition of seed-colonizing microbial communities on seeds, 2) Determine the dynamics of development of microbial communities on seeds, and 3) Determine and compare the composition of seed-colonizing microbial communities with the composition of those in the soil and rhizosphere of the plants. Revisions to objectives: Our initial work on this project was hampered by the presence of native Pythium species in the soils we were using (in the US), preventing us from getting accurate assessments of spermosphere microbial communities. In our initial work, we tried to get around this problem by focusing on water potentials that might reduce damage from native Pythium species. This also prompted some initial investigation of the oomycete communities associated seedlings in this soil. However, for this work to proceed in a way that would allow us to examine seed-colonizing communities on healthy plants, we needed to either physically treat soils or amend soils with composts to suppress damage from Pythium. In the end, we followed the compost amendment line of investigation, which took us away from our initial objectives, but led to interesting work focusing on seed-associated microbial communities and their functional significance to seed-infecting pathogens. Work done in Israel was using suppressive compost amended potting mix throughout the study and did not have such problems. Our work focused on the following objectives: 1) to determine whether different plant species support a microbial induced suppression of Pythium damping-off, 2) to determine whether compost microbes that colonize seeds during early stages of seed germination can adequately explain levels of damping-off suppression observed, 3) to characterize cucumber seed-colonizing microbial communities that give rise to the disease suppressive properties, 4) assess carbon competition between seed-colonizing microbes and Pythium sporangia as a means of explaining Pythium damping-off suppression. Background: Earlier work demonstrated that seed-colonizing microbes might explain Pythium suppression. Yet these seed-colonizing microbial communities have never been characterized and their functional significance to Pythium damping-off suppression is not known. Our work set out to confirm the disease suppressive properties of seed-colonizing microbes, to characterize communities, and begin to determine the mechanisms by which Pythium suppression occurs. Major Conclusions: Compost-induced suppression of Pythium damping-off of cucumber and wheat can be explained by the bacterial consortia colonizing seeds within 8 h of sowing. Suppression on pea was highly variable. Fungi and archaea play no role in disease suppression. Potentially significant bacterial taxa are those with affinities to Firmicutes, Actinobacteria, and Bacteroidetes. Current sequencing efforts are trying to resolve these taxa. Seed colonizing bacteria suppress Pythium by carbon competition, allowing sporangium germination by preventing the development of germ tubes. Presence of Pythium had a strong effect on microbial community on the seed.

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San Juan, Jose, e Maria L. No. Development of Ultra-High Mechanical Damping Structures Based on the Nano-Scale Properties of Shape Memory Alloys. Fort Belvoir, VA: Defense Technical Information Center, luglio 2013. http://dx.doi.org/10.21236/ada610199.

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Pisani, William, Dane Wedgeworth, Michael Roth, John Newman e Manoj Shukla. Exploration of two polymer nanocomposite structure-property relationships facilitated by molecular dynamics simulation and multiscale modeling. Engineer Research and Development Center (U.S.), marzo 2023. http://dx.doi.org/10.21079/11681/46713.

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Polyamide 6 (PA6) is a semi-crystalline thermoplastic used in many engineering applications due to good strength, stiffness, mechanical damping, wear/abrasion resistance, and excellent performance-to-cost ratio. In this report, two structure-property relationships were explored. First, carbon nanotubes (CNT) and graphene (G) were used as reinforcement molecules in simulated and experimentally prepared PA6 matrices to improve the overall mechanical properties. Molecular dynamics (MD) simulations with INTERFACE and reactive INTERFACE force fields (IFF and IFF-R) were used to predict bulk and Young's moduli of amorphous PA6-CNT/G nanocomposites as a function of CNT/G loading. The predicted values of Young's modulus agree moderately well with the experimental values. Second, the effect of crystallinity and crystal form (α/γ) on mechanical properties of semi-crystalline PA6 was investigated via a multiscale simulation approach. The National Aeronautics and Space Administration, Glenn Research Center's micromechanics software was used to facilitate the multiscale modeling. The inputs to the multiscale model were the elastic moduli of amorphous PA6 as predicted via MD and calculated stiffness matrices from the literature of the PA6 α and γ crystal forms. The predicted Young's and shear moduli compared well with experiment.

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Lokke, Arnkjell, e Anil Chopra. Direct-Finite-Element Method for Nonlinear Earthquake Analysis of Concrete Dams Including Dam–Water–Foundation Rock Interaction. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, marzo 2019. http://dx.doi.org/10.55461/crjy2161.

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Evaluating the seismic performance of concrete dams requires nonlinear dynamic analysis of two- or three-dimensional dam–water–foundation rock systems that include all the factors known to be significant in the earthquake response of dams. Such analyses are greatly complicated by interaction between the structure, the impounded reservoir and the deformable foundation rock that supports it, and the fact that the fluid and foundation domains extend to large distances. Presented in this report is the development of a direct finite-element (FE) method for nonlinear earthquake analysis of two- and three-dimensional dam–water–foundation rock systems. The analysis procedure applies standard viscous-damper absorbing boundaries to model the semi-unbounded fluid and foundation domains, and specifies at these boundaries effective earthquake forces determined from a ground motion defined at a control point on the ground surface. This report is organized in three parts, with a common notation list, references, and appendices at the end of the report. Part I develops the direct FE method for 2D dam–water–foundation rock systems. The underlying analytical framework of treating dam–water–foundation rock interaction as a scattering problem, wherein the dam perturbs an assumed "free-field" state of the system, is presented, and by applying these concepts to a bounded FE model with viscous-damper boundaries to truncate the semi-unbounded domains, the analysis procedure is derived. Step-by-step procedures for computing effective earthquake forces from analysis of two 1D free-field systems are presented, and the procedure is validated by computing frequency response functions and transient response of an idealized dam–water–foundation rock system and comparing against independent benchmark results. This direct FE method is generalized to 3D systems in Part II of this report. While the fundamental concepts of treating interaction as a scattering problem are similar for 2D and 3D systems, the derivation and implementation of the method for 3D systems is much more involved. Effective earthquake forces must now be computed by analyzing a set of 1D and 2D systems derived from the boundaries of the free-field systems, which requires extensive book-keeping and data transfer for large 3D models. To reduce these requirements and facilitate implementation of the direct FE method for 3D systems, convenient simplifications of the procedure are proposed and their effectiveness demonstrated. Part III of the report proposes to use the direct FE method for conducting the large number of nonlinear response history analyses (RHAs) required for performance-based earthquake engineering (PBEE) of concrete dams, and discusses practical modeling considerations for two of the most influential aspects of these analyses: nonlinear mechanisms and energy dissipation (damping). The findings have broad implications for modeling of energy dissipation and calibration of damping values for concrete dam analyses. At the end of Part III, the direct FE method is implemented with a commercial FE program and used to compute the nonlinear response of an actual arch dam. These nonlinear results, although limited in their scope, demonstrate the capabilities and effectiveness of the direct FE method to compute the types of nonlinear engineering response quantities required for PBEE of concrete dams.

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5

Moghimi, Gholamreza, e Nicos Makris. Response Modification of Structures with Supplemental Rotational Inertia. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, gennaio 2024. http://dx.doi.org/10.55461/tihv1701.

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Tall, multistory, buildings are becoming increasingly popular in large cities as a result of growing urbanization trends (United Nations Department of Economic and Social Affairs 2018). As cities continue to grow, many of them along the coasts of continents which are prone to natural hazards, the performance of tall, flexible buildings when subjected to natural hazards is a pressing issue with engineering relevance. The performance of structures when subjected to dynamic loads can be enhanced with various response modification strategies which have been traditionally achieved with added stiffness, flexibility, damping and strength (Kelly et al. 1972; Skinner et al. 1973, 1974; Clough and Penzien 1975; Zhang et al. 1989; Aiken 1990; Whittaker et al. 1991; Makris et al. 1993a,b; Skinner et al. 1993; Inaudi and Makris 1996; Kelly 1997; Soong and Dargush 1997; Constantinou et al. 1998; Makris and Chang 2000a; Chang and Makris 2000; Black et al. 2002, 2003; Symans et al. 2008; Sarlis et al. 2013; Tena-Colunga 1997). Together with the elastic spring that produces a force proportional to the relative displacement of its end-nodes and the viscous dashpot that produces a force proportional to the relative velocity of its end-nodes; the inerter produces a force proportional to the relative acceleration of its end-nodes and emerges as the third elementary mechanical element (in addition to the spring and dashpot) capable for modifying structural response. Accordingly, in this report we examine the seismic performance of multistory and seismically isolated structures when equipped with inerters. In view that the inerter emerges as the third elementary mechanical element for the synthesis of mechanical networks, in Chapter 2 we derive the basic frequency- and time-response functions of the inerter together with these of the two-parameter inertoelastic and inertoviscous mechanical networks. Chapter 3 examines the response of a two-degree-of-freedom (2DOF) structure where the first story is equipped with inerters. Both cases of a stiff and a compliant support of the inerters are examined. The case of two parallel clutching inerters is investigated and the study concludes that as the compliance of the frame that supports the inerters increases, the use of a single inerter offers more favorable response other than increasing the force transferred to the support frame. Chapter 4 examines the seismic response analysis of the classical two-degree-of-freedom isolated structure with supplemental rotational inertia (inerter) in its isolation system. The analysis shows that for the “critical” amount of rotational inertia which eliminates the participation of the second mode, the effect of this elimination is marginal on the structural response since the participation of the second mode is invariably small even when isolation systems without inerters are used. Our study, upon showing that the reaction force at the support of the inerter is appreciable, proceeds with a non-linear response analysis that implements a state-space formulation which accounts for the bilinear behavior of practical isolation system (single concave sliding bearings or lead-rubber bearings) in association with the compliance of the support of the inerter. Our study concludes that supplemental rotational inertia aggravates the displacement and acceleration response of the elastic superstructure and as a result, for larger isolation periods (Tb > 2.5s) the use of inerters in isolation systems is not recommended. Chapter 5 first examines the response analysis of a SDOF elastoplastic and bilinear structure and reveals that when the yielding structure is equipped with supplemental rotational inertia, the equal- displacement rule is valid starting from lower values of the pre-yielding period given that the presence of inerters lengthens the apparent pre-yielding period. The analysis concludes that sup- plemental rotational inertia emerges as an attractive response modification strategy for elastoplastic and bilinear SDOF structures with pre-yielding periods up to T1 = 1.5sec. For larger pre-yielding periods (say T1 > 2.0sec), the effectiveness of inerters to suppress the inelastic response of 2DOF yielding structures reduces; and for very flexible first stories; as in the case of isolated structures examined in chapter 4, the use of inerter at the first level (isolation system) is not recommended. Finally, chapter 6 shows that, in spite of the reduced role of inerters when placed at floor levels other than the first level (they no-longer suppress the induced ground acceleration nor they can eliminate the participation of higher modes), they still manifest a unique role since it is not possible to replace a structure with solitary inerters at higher levels with an equivalent traditional structure without inerters.

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Wu, Yingjie, Selim Gunay e Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/ytgv8834.

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Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.

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Galili, Naftali, Roger P. Rohrbach, Itzhak Shmulevich, Yoram Fuchs e Giora Zauberman. Non-Destructive Quality Sensing of High-Value Agricultural Commodities Through Response Analysis. United States Department of Agriculture, ottobre 1994. http://dx.doi.org/10.32747/1994.7570549.bard.

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The objectives of this project were to develop nondestructive methods for detection of internal properties and firmness of fruits and vegetables. One method was based on a soft piezoelectric film transducer developed in the Technion, for analysis of fruit response to low-energy excitation. The second method was a dot-matrix piezoelectric transducer of North Carolina State University, developed for contact-pressure analysis of fruit during impact. Two research teams, one in Israel and the other in North Carolina, coordinated their research effort according to the specific objectives of the project, to develop and apply the two complementary methods for quality control of agricultural commodities. In Israel: An improved firmness testing system was developed and tested with tropical fruits. The new system included an instrumented fruit-bed of three flexible piezoelectric sensors and miniature electromagnetic hammers, which served as fruit support and low-energy excitation device, respectively. Resonant frequencies were detected for determination of firmness index. Two new acoustic parameters were developed for evaluation of fruit firmness and maturity: a dumping-ratio and a centeroid of the frequency response. Experiments were performed with avocado and mango fruits. The internal damping ratio, which may indicate fruit ripeness, increased monotonically with time, while resonant frequencies and firmness indices decreased with time. Fruit samples were tested daily by destructive penetration test. A fairy high correlation was found in tropical fruits between the penetration force and the new acoustic parameters; a lower correlation was found between this parameter and the conventional firmness index. Improved table-top firmness testing units, Firmalon, with data-logging system and on-line data analysis capacity have been built. The new device was used for the full-scale experiments in the next two years, ahead of the original program and BARD timetable. Close cooperation was initiated with local industry for development of both off-line and on-line sorting and quality control of more agricultural commodities. Firmalon units were produced and operated in major packaging houses in Israel, Belgium and Washington State, on mango and avocado, apples, pears, tomatoes, melons and some other fruits, to gain field experience with the new method. The accumulated experimental data from all these activities is still analyzed, to improve firmness sorting criteria and shelf-life predicting curves for the different fruits. The test program in commercial CA storage facilities in Washington State included seven apple varieties: Fuji, Braeburn, Gala, Granny Smith, Jonagold, Red Delicious, Golden Delicious, and D'Anjou pear variety. FI master-curves could be developed for the Braeburn, Gala, Granny Smith and Jonagold apples. These fruits showed a steady ripening process during the test period. Yet, more work should be conducted to reduce scattering of the data and to determine the confidence limits of the method. Nearly constant FI in Red Delicious and the fluctuations of FI in the Fuji apples should be re-examined. Three sets of experiment were performed with Flandria tomatoes. Despite the complex structure of the tomatoes, the acoustic method could be used for firmness evaluation and to follow the ripening evolution with time. Close agreement was achieved between the auction expert evaluation and that of the nondestructive acoustic test, where firmness index of 4.0 and more indicated grade-A tomatoes. More work is performed to refine the sorting algorithm and to develop a general ripening scale for automatic grading of tomatoes for the fresh fruit market. Galia melons were tested in Israel, in simulated export conditions. It was concluded that the Firmalon is capable of detecting the ripening of melons nondestructively, and sorted out the defective fruits from the export shipment. The cooperation with local industry resulted in development of automatic on-line prototype of the acoustic sensor, that may be incorporated with the export quality control system for melons. More interesting is the development of the remote firmness sensing method for sealed CA cool-rooms, where most of the full-year fruit yield in stored for off-season consumption. Hundreds of ripening monitor systems have been installed in major fruit storage facilities, and being evaluated now by the consumers. If successful, the new method may cause a major change in long-term fruit storage technology. More uses of the acoustic test method have been considered, for monitoring fruit maturity and harvest time, testing fruit samples or each individual fruit when entering the storage facilities, packaging house and auction, and in the supermarket. This approach may result in a full line of equipment for nondestructive quality control of fruits and vegetables, from the orchard or the greenhouse, through the entire sorting, grading and storage process, up to the consumer table. The developed technology offers a tool to determine the maturity of the fruits nondestructively by monitoring their acoustic response to mechanical impulse on the tree. A special device was built and preliminary tested in mango fruit. More development is needed to develop a portable, hand operated sensing method for this purpose. In North Carolina: Analysis method based on an Auto-Regressive (AR) model was developed for detecting the first resonance of fruit from their response to mechanical impulse. The algorithm included a routine that detects the first resonant frequency from as many sensors as possible. Experiments on Red Delicious apples were performed and their firmness was determined. The AR method allowed the detection of the first resonance. The method could be fast enough to be utilized in a real time sorting machine. Yet, further study is needed to look for improvement of the search algorithm of the methods. An impact contact-pressure measurement system and Neural Network (NN) identification method were developed to investigate the relationships between surface pressure distributions on selected fruits and their respective internal textural qualities. A piezoelectric dot-matrix pressure transducer was developed for the purpose of acquiring time-sampled pressure profiles during impact. The acquired data was transferred into a personal computer and accurate visualization of animated data were presented. Preliminary test with 10 apples has been performed. Measurement were made by the contact-pressure transducer in two different positions. Complementary measurements were made on the same apples by using the Firmalon and Magness Taylor (MT) testers. Three-layer neural network was designed. 2/3 of the contact-pressure data were used as training input data and corresponding MT data as training target data. The remaining data were used as NN checking data. Six samples randomly chosen from the ten measured samples and their corresponding Firmalon values were used as the NN training and target data, respectively. The remaining four samples' data were input to the NN. The NN results consistent with the Firmness Tester values. So, if more training data would be obtained, the output should be more accurate. In addition, the Firmness Tester values do not consistent with MT firmness tester values. The NN method developed in this study appears to be a useful tool to emulate the MT Firmness test results without destroying the apple samples. To get more accurate estimation of MT firmness a much larger training data set is required. When the larger sensitive area of the pressure sensor being developed in this project becomes available, the entire contact 'shape' will provide additional information and the neural network results would be more accurate. It has been shown that the impact information can be utilized in the determination of internal quality factors of fruit. Until now,

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8

EXPERIMENTAL STUDY OF HYSTERETIC BEHAVIOR OF RESILIENT PREFABRICATED STEEL FRAMES WITH AND WITHOUT INTERMEDIATE COLUMNS. The Hong Kong Institute of Steel Construction, settembre 2022. http://dx.doi.org/10.18057/ijasc.2022.18.3.9.

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The research innovatively proposed a seismic resilient structural system including a prefabricated self-centering steel frame (PSC) and an intermediate column with a friction damper (CD). The CD, installed in the mid-span beam of the PSC, was expected to provide additional stiffness and damping, The seismic performance of the newly-developed resilient structural system thus can be greatly improved. This paper stated the experimental study on the hysteretic behaviors of the newly-developed system. Comparative pseudo-dynamic tests were conducted for the validation where two systems, a PSC with CD and a PSC without CD, were tested respectively. The testing results indicated that a PSC with CD has better seismic performance for long-span structures under catastrophic earthquakes’ attack. The CD overall provided additional stiffness for requirements of earthquake fortification criteria. The friction damper, part of CD greatly improves the damping effect together with the energy-dissipation bolts. The small residual rotations of beam-column connections on the PSC subsystem provides a satisfactory self-centering mechanism. Moreover, the steel strands of the resilient structural system can maintain the elasticity even after the highest-intensity earthquake. In turn, the satisfactory seismic performance of the proposed PSC with CD structural system validated. This research developed a series of design formula for the T-plate and L-plate friction damper in the CD to guarantee the designed seismic performance of the proposed seismic resilient structural system. The theoretical hysteresis curve of the system was proposed for the future design specification.

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