scholarly journals Seismic Forces in Ancillary Components Supported on Piers and Wharves

2018 ◽  
Vol 34 (2) ◽  
pp. 741-758 ◽  
Author(s):  
Rakesh K. Goel
Keyword(s):  
Simple Procedure ◽  
Single Mode ◽  
Primary System ◽  
Elastic Model ◽  
Secondary System ◽  
Marine Structures ◽  
Acceleration Amplification ◽  
Marine Structure ◽  
Secondary Systems ◽  
Seismic Forces

This paper presents a simple procedure to estimate seismic forces in ancillary components (secondary systems) supported on marine structures such as piers, wharves, and marine oil terminals (primary systems). Since many such marine structures can be idealized as single-degree-of-freedom (SDOF) systems, this study uses a simple linear-elastic model with two DOF, one representing the marine structure and the other representing the ancillary component. This study shows that acceleration at the base of the secondary system is approximately equal to spectral acceleration at the fundamental period of the primary system. It also proposes a formula, which is an improvement over current ASCE 7-10 recommendations, to estimate acceleration amplification in the secondary system due to its flexibility when mass and period ratios of the secondary and primary systems are known. The procedure in this paper is strictly applicable to marine structures for which primarily a single mode contributes to seismic response.

On the Nonstationary Response of Stochastically Excited Secondary Systems

1987 ◽  
Vol 54 (3) ◽  
pp. 688-694 ◽  
Author(s):  
W. D. Iwan ◽  
K. S. Smith
Keyword(s):  
Closed Form Expression ◽  
Primary System ◽  
Mean Square ◽  
Stochastic Excitation ◽  
Secondary System ◽  
Form Expression ◽  
Combined System ◽  
Nonstationary Response ◽  
Secondary Systems ◽  
The Mean

The envelope response of a secondary system is derived for the case where the primary system is subjected to nonstationary stochastic excitation. An approximate closed form expression for the mean square envelope response is obtained for the case of transient response to stationary excitation when the primary and secondary systems are noninteracting. When the combined system is classically damped, the effect of the interaction is described by the introduction of an equivalent noninteracting system. The analytical results are compared with results of numerical simulations.

Optimal Performance Comparison of Nonlinear Energy Sinks and Linear Tuned Mass Dampers

2021 ◽  
Author(s):  
Ivan Yegorov (Egorov) ◽  
Austin Uden ◽  
Daniil Yurchenko
Keyword(s):  
Nonlinear Energy Sink ◽  
Free Vibrations ◽  
Performance Comparison ◽  
Optimal Performance ◽  
Primary System ◽  
Secondary System ◽  
Impulsive Excitation ◽  
Secondary Systems ◽  
Energy Sink ◽  
Nonlinear Energy

Abstract This paper studies a targeted energy transfer (TET) mechanism for a two-degree-of-freedom (TDOF) model in free vibration. The model comprises a primary linear system and a secondary system in the form of an energy sink which can be nonlinear. The free vibrations are considered subject to an impulsive excitation exerted on the primary system, leading to a nonzero initial velocity. The goal is to obtain the spring parameters in the nonlinear energy sink (NES) so as to maximize an energy dissipation measure (EDM) representing the percentage of impulsive energy that is absorbed and dissipated in the NES. A global optimization algorithm is used for this purpose. The optimal performance is assessed for the purely linear, linear-cubic, and purely cubic configurations of the spring connecting the primary and secondary systems. The corresponding results are compared with each other. The optimization process is performed for the EDM averaged over given ranges of the initial impulse and natural frequency in the primary system. It is shown that the type of the optimal configuration can vary depending on these ranges.

An infinite-server queue subject to an extraneous phase process and related models

1981 ◽  
Vol 18 (1) ◽  
pp. 236-244 ◽  
Author(s):  
P. Purdue ◽  
D. Linton
Keyword(s):  
Original System ◽  
Primary System ◽  
Secondary System ◽  
State Behavior ◽  
Infinite Server ◽  
Server Queue ◽  
Secondary Systems ◽  
Stage System ◽  
The Mean ◽  
Bulk Arrival

We consider an infinite-server queueing system in an extraneous environment. Initially it is shown that the systems of interest can be decomposed into a two-stage system. The primary system is an infinite-server queue with many customer types subject to a clearing mechanism. The secondary system is a special type of bulk-arrival, infinite-server queue. We derive results for the primary and secondary systems separately and combine the results to find the mean steady-state behavior of the original system.

An infinite-server queue subject to an extraneous phase process and related models

1981 ◽  
Vol 18 (01) ◽  
pp. 236-244 ◽  
Author(s):  
P. Purdue ◽  
D. Linton
Keyword(s):  
Original System ◽  
Primary System ◽  
Secondary System ◽  
State Behavior ◽  
Infinite Server ◽  
Server Queue ◽  
Secondary Systems ◽  
Stage System ◽  
The Mean ◽  
Bulk Arrival

We consider an infinite-server queueing system in an extraneous environment. Initially it is shown that the systems of interest can be decomposed into a two-stage system. The primary system is an infinite-server queue with many customer types subject to a clearing mechanism. The secondary system is a special type of bulk-arrival, infinite-server queue. We derive results for the primary and secondary systems separately and combine the results to find the mean steady-state behavior of the original system.

A Stochastic Analysis for Multiple Supported MDOF Secondary Systems

1995 ◽  
Vol 117 (2) ◽  
pp. 182-188 ◽  
Author(s):  
A. Saudy ◽  
T. Aziz ◽  
A. Ghobarah
Keyword(s):  
Dynamic Loading ◽  
Stochastic Analysis ◽  
Dynamic Interaction ◽  
Primary System ◽  
Secondary System ◽  
Theoretical Formulation ◽  
Interaction Forces ◽  
Numerical Examples ◽  
Secondary Systems ◽  
System Properties

A new stochastic analysis is developed to estimate the response of multiple supported mdof secondary systems to dynamic loading. In the proposed stochastic analysis, the effect of the dynamic interaction between the secondary and primary systems is included. An outline for the theoretical formulation of the proposed stochastic analysis is presented. The assumptions adopted in the formulation are discussed. The dynamic interaction is shown to comprise two effects: the effect of the interaction forces arising at the attachment points, and the effect of the changes in the primary system properties resulting from the attachment of the secondary system. In addition, numerical examples are provided to demonstrate the validity of the proposed analysis.

Vibration control of network-based offshore structures subject to earthquakes

2021 ◽  
pp. 014233122110259
Author(s):  
Hua-Nv Feng ◽  
Bao-Lin Zhang ◽  
Yan-Dong Zhao ◽  
Hui Ma ◽  
Hao Su ◽  
...  
Keyword(s):  
Sufficient Conditions ◽  
Offshore Structures ◽  
Delay Systems ◽  
Linear Matrix ◽  
Seismic Responses ◽  
Marine Structures ◽  
Damping Control ◽  
Marine Structure ◽  
Uncertain Model ◽  
Control Scheme

Marine structures are inevitably influenced by parametric perturbations as well as multiple external loadings. Among these loadings, earthquake is generally more destructive and unpredictable than others. It is significant to develop effective active control schemes to guarantee the safety, stability, and integrity of marine structures subject to earthquakes and parametric perturbations. In this paper, the problem of networked [Formula: see text] robust damping control is addressed to stabilize a marine structure subject to earthquakes. First, in consideration of perturbations of the structure parameters, an uncertain model of the networked marine structure under earthquakes is presented. Second, a robust networked [Formula: see text] control scheme is presented to suppress seismic responses of the structure. By using stability theory of time-delay systems, several sufficient conditions on robust stability of the networked marine structure system are obtained, and the linear matrix inequality methods are utilized to solve the gain matrix of the controller. Finally, simulation indicates that compared with the traditional robust [Formula: see text] control and the proposed networked [Formula: see text] control, the seismic responses amplitudes of the marine structure under the two controllers are almost the same, while the latter is more economic than the former.

The Two-Degree-of-Freedom Tuned-Mass Damper for Suppression of Single-Mode Vibration Under Random and Harmonic Excitation

2005 ◽  
Vol 128 (1) ◽  
pp. 56-65 ◽  
Author(s):  
Lei Zuo ◽  
Samir A. Nayfeh
Keyword(s):  
Vibration Suppression ◽  
Single Mode ◽  
Tuned Mass Damper ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Primary System ◽  
H Infinity ◽  
Mass Damper ◽  
Mode Vibration ◽  
Two Degree Of Freedom

Whenever a tuned-mass damper is attached to a primary system, motion of the absorber body in more than one degree of freedom (DOF) relative to the primary system can be used to attenuate vibration of the primary system. In this paper, we propose that more than one mode of vibration of an absorber body relative to a primary system be tuned to suppress single-mode vibration of a primary system. We cast the problem of optimization of the multi-degree-of-freedom connection between the absorber body and primary structure as a decentralized control problem and develop optimization algorithms based on the H2 and H-infinity norms to minimize the response to random and harmonic excitations, respectively. We find that a two-DOF absorber can attain better performance than the optimal SDOF absorber, even for the case where the rotary inertia of the absorber tends to zero. With properly chosen connection locations, the two-DOF absorber achieves better vibration suppression than two separate absorbers of optimized mass distribution. A two-DOF absorber with a negative damper in one of its two connections to the primary system yields significantly better performance than absorbers with only positive dampers.

Secondary Use of Radio Spectrum by High Altitude Platform

2013 ◽  
pp. 290-300
Author(s):  
Zhe Yang ◽  
Abbas Mohammed
Keyword(s):  
High Altitude ◽  
Spectrum Sharing ◽  
Radio Spectrum ◽  
Primary System ◽  
Secondary System ◽  
Secondary Use ◽  
Terrestrial System ◽  
High Altitude Platform ◽  
Radio Resources ◽  
Systems Simulation

Traditional spectrum licensing enables guaranteed quality of service but could lead to inefficient use of the spectrum. The quest to achieve higher usage efficiency for the spectrum has been the hottest research topic worldwide recently. More efficient transmission technologies are being developed, but they alone cannot solve problems of spatially and temporally underused spectrum and radio resources. In this chapter, the authors review major challenges in traditional spectrum sharing and mechanisms to optimize the efficiency of spectrum usage. They investigate and assess incentives of a primary terrestrial system and secondary system based on a High-Altitude Platform (HAP) to share spectrum towards common benefits. The primary terrestrial system is defined to have exclusive rights to access the spectrum, which is shared by the secondary HAP system upon request. The Markov chain is presented to model two spectrum-sharing scenarios and evaluate the performance of spectrum sharing between primary terrestrial and secondary HAP systems. Simulation results show that to reserve an amount of spectrum from a primary system could encourage spectrum sharing with a secondary system, which has a frequent demand on requesting spectrum resources.

scholarly journals Methoden zur Bestimmung von Wirkungsquerschnitten für Spinaustausch und Depolarisation indirekt optisch gepumpter Atome

1971 ◽  
Vol 26 (10) ◽  
pp. 1571-1577
Author(s):  
A. Assfalg ◽  
J. Fricke ◽  
J. Haas ◽  
E. Lüscher
Keyword(s):  
Phase Angle ◽  
Cross Sections ◽  
Nuclear Spin ◽  
Spin Exchange ◽  
Light Transmission ◽  
Primary System ◽  
Buffer Gas ◽  
Secondary System ◽  
Spin Depolarization

Abstract Two methods are described to derive cross sections for spin exchange and spin depolarization of an indirectly pumped alkali vapor with zero nuclear spin. Either pulsed or sinusoidally modulated radiofrequency can be used to destroy the polarization of the indirectly pumped (secondary) system, while the intensity of the transmitted pumping light is observed. Cross sections follow from the indirectly produced depolarization of the primary system i. e. from the change in pumping light transmission or from the phase angle between the rf modulation and the intensity oscillations of the transmitted light. The quality of the two methods is tested by deriving cross sections for spin exchange between Cs and Rb and for depolarization of Rb in Argon buffer gas.

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