Effect of Elastomeric Snubber Properties on Seismic Response of Vibration-Isolated Mechanical Equipment: An Experimental Study

2008 ◽  
Vol 24 (2) ◽  
pp. 387-403 ◽  
Author(s):  
Saeed Fathali ◽  
André Filiatrault
Keyword(s):  
Seismic Response ◽  
Contact Surface ◽  
High Amplitude ◽  
Relative Displacement ◽  
Mechanical Equipment ◽  
Gap Size ◽  
Displacement Response ◽  
Dynamic Forces ◽  
Centrifugal Chiller ◽  
Input Motion

Earthquake-simulator experiments were conducted on a liquid centrifugal chiller supported by four isolation/restraint systems with built-in elastomeric snubbers. The test plan incorporated variations of input motion amplitudes and snubber properties to investigate their effect on three response quantities: peak dynamic forces induced into the snubbers, peak acceleration, and peak relative displacement response of the equipment. The elastomeric snubbers limited the displacement responses of the vibration-isolated equipment at the expense of excessive dynamic forces and amplification of the equipment acceleration response. The snubber gap size was the most influential property on the response quantities. For high-amplitude input motions, all the response quantities increased with an increase of the gap size. Due to the compressibility of the snubber elastomeric contact-surface, the actual gap size was always larger than the nominal gap size. Even with a nominal gap size less than 0.25 in., the seismic response of the equipment was substantially different from the seismic response of rigidly mounted equipment. Compared to snubbers with constant contact-surface, snubbers with expanding contact-surface resulted in lower dynamic forces. The thicker and softer contact-surface could lower the dynamic forces induced into the snubbers but resulted in larger relative displacement response of the equipment.

Effects of Fling Step and Forward Directivity on Seismic Response of Buildings

2006 ◽  
Vol 22 (2) ◽  
pp. 367-390 ◽  
Author(s):  
Erol Kalkan ◽  
Sashi K. Kunnath
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
High Amplitude ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Damage Potential ◽  
Near Fault ◽  
Forward Directivity ◽  
Fling Step ◽  
Far Fault

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

scholarly journals Near-Fault Seismic Response Analysis of Bridges Considering Girder Impact and Pier Size

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 704
Author(s):  
Wenjun An ◽  
Guquan Song ◽  
Shutong Chen
Keyword(s):  
Seismic Response ◽  
Bending Moment ◽  
Expansion Method ◽  
Response Analysis ◽  
Seismic Action ◽  
Transient Wave ◽  
Cross Sectional ◽  
Displacement Response ◽  
Near Fault ◽  
Continuous Girder Bridge

Given the influence of near-fault vertical seismic action, we established a girder-spring-damping-rod model of a double-span continuous girder bridge and used the transient wave function expansion method and indirect modal function method to calculate the seismic response of the bridge. We deduced the theoretical solution for the vertical and longitudinal contact force and displacement response of the bridge structure under the action of the near-fault vertical seismic excitation, and we analyzed the influence of the vertical separation of the bridge on the bending failure of the pier. Our results show that under the action of a near-fault vertical earthquake, pier-girder separation will significantly alter the bridge’s longitudinal displacement response, and that neglecting this separation may lead to the underestimation of the pier’s bending damage. Calculations of the bending moment at the bottom of the pier under different pier heights and cross-sectional diameters showed that the separation of the pier and the girder increases the bending moment at the pier’s base. Therefore, the reasonable design of the pier size and tensile support bearing in near-fault areas may help to reduce longitudinal damage to bridges.

Frequency Response Analysis of Piecewise Nonlinear Vibration Isolator

2005 ◽  
Author(s):  
Patrick Stahl ◽  
G. Nakhaie Jazar
Keyword(s):  
Low Frequency ◽  
High Amplitude ◽  
Relative Displacement ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
State Behavior ◽  
Vibration Isolators ◽  
Short Period ◽  
Secondary Suspension ◽  
Low Amplitude

Non-smooth piecewise functional isolators are smart passive vibration isolators that can provide effective isolation for high frequency/low amplitude excitation by introducing a soft primary suspension, and by preventing a high relative displacement in low frequency/high amplitude excitation by introducing a relatively damped secondary suspension. In this investigation a linear secondary suspension is attached to a nonlinear primary suspension. The primary is assumed to be nonlinear to model the inherent nonlinearities involved in real suspensions. However, the secondary suspension comes into action only during a short period of time, and in mall domain around resonance. Therefore, a linear assumption for the secondary suspension is reasonable. The dynamic behavior of the system subject to a harmonic base excitation has been analyzed utilizing the analytic results derived by applying the averaging method. The analytic results match very well in the transition between the two suspensions. A sensitivity analysis has shown the effect of varying dynamic parameters in the steady state behavior of the system.

Kalman filter identification method for micro-vibration transfer paths of satellites

2021 ◽  
pp. 095441002110533
Author(s):  
Yan Shen ◽  
Yang Xu ◽  
Xiaowei Sheng ◽  
Xianbo Yin
Keyword(s):  
Kalman Filter ◽  
Correlation Coefficients ◽  
Vibration Signal ◽  
Satellite System ◽  
Solar Array ◽  
Target Point ◽  
Mechanical Equipment ◽  
Displacement Response ◽  
Transfer Path ◽  
Identification Method

Micro-vibrations on-board a satellite have degrading effects on the performance of certain payloads like observation cameras. The major sources of vibrations include momentum wheels, solar array drives, other rotary mechanical equipment, etc. These vibrations result in loss of the pointing precision and image quality of the payload through intricate transfer paths. To improve the accuracy of a satellite system with many vibration sources and complex transfer paths, it is necessary to determine the main transfer path of vibration. In this study, a path identification method is proposed and applied to the transfer system from the momentum wheel to the camera mount. First, the observer/Kalman filter identification (OKID) algorithm is used to acquire the state-space equation of each path subsystem. Then, the subsystem order is obtained based on the slope of the singular entropy increment. In the next phase, combined with the measured disturbance force of the momentum wheel, the displacement response of the target point is predicted. Finally, the dominant transfer path of vibration is achieved by calculating the vibration contribution of each path to the response point. The results indicate that the dominant transfer path is the axial path of the horizontal momentum wheel, which contributes to the vibration of the camera mount at most. Effective vibration reduction measures should be taken to this path to suppress the vibration signal. In comparing the identified displacement response with the finite element response of the camera mount under different noise conditions, the correlation coefficients are >0.85, which proves the accuracy and anti-noise capability of the identification method.

Identifying Cable Tension Loss and Deck Damage in a Cable-Stayed Bridge Using a Moving Vehicle

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Shih-Hsun Yin ◽  
Chung-Yu Tang
Keyword(s):  
Computational Study ◽  
Vertical Displacement ◽  
Relative Displacement ◽  
Future Research ◽  
Integration Scheme ◽  
Time Step ◽  
Cable Tension ◽  
Displacement Response ◽  
Cable Stayed Bridge ◽  
Response Vector

This paper presents a computational study on a new method of detecting multiple simultaneous damages in a cable-stayed bridge by use of the analysis of the vertical dynamic response of a vehicle passing the bridge. First, the study uses a finite-element method to simulate the vehicle cable-stayed bridge system. Then, the vertical vibration interaction between the bridge and the vehicle is solved by a time-step integration scheme. In this research, we consider that two kinds of damage including cable tension loss and deck damage may occur simultaneously at different locations. The differences between the vertical displacement responses of a vehicle passing the damaged bridge and the healthy bridge are sampled and called the relative displacement response vector of the vehicle. The proper orthogonal decomposition (POD) is utilized to decompose the relative displacement response vector of the vehicle passing the bridge with unknown multiple damages into an optimal set of basis vectors formed from the ones of the vehicle moving over the known damaged bridges. The associated system parameters variation with the unknown multiple damages can be reconstructed further. Discussions are given concerning the feasibility and limitation of the proposed detection technique as well as directions for future research.

Energy Dissipation of Damper Rings for Thin-Walled Gears

2019 ◽  
Author(s):  
Zichao Li ◽  
Yanrong Wang ◽  
Xianghua Jiang ◽  
Hang Ye ◽  
Weichao Yang
Keyword(s):  
Energy Dissipation ◽  
Contact Surface ◽  
Strain Difference ◽  
Damping Ratio ◽  
Harmonic Balance Method ◽  
Axial Direction ◽  
Relative Displacement ◽  
Axial Displacement ◽  
Hysteresis Curve ◽  
Thin Walled

Abstract When the gear generates a nodal mode shape vibration, there are two directions of possible relative displacement between the corresponding points on the contact surface of the damper ring and the damper groove, which are circumferential direction and axial direction respectively. In this paper, the relative displacement of the damper ring and the damper groove are considered in two directions, and the calculation method of energy dissipation is proposed. When the nodal vibration occurs in the gear, due to the existence of the strain difference between the damper ring and the damper groove on the contact surface, circumferential slip of partial area would occur. The energy dissipation in one vibration cycle is accurately determined by analytical solution. Since the aviation gears are mostly thin-walled structures, the axial displacement is large when resonance occurs. Based on the discrete damper ring model which considers interaction between every segment of the ring, the first-order harmonic balance method is used to calculate the axial displacement of the damper ring under the given gear rim amplitude. And then the hysteresis curve area of each discrete segment on the contact surface is summed to obtain energy dissipation in one vibration cycle. In this paper, based on the energy method, the damping effect of the damper ring is predicted. The damping ratio curve obtained by energy dissipation in two directions is compared and analyzed. The occurrence conditions of the two directions of possible relative displacement and the influence of the damper ring parameters on both situations are summarized.

scholarly journals Permeability Evolution of Fractured Rock Subjected to Cyclic Axial Load Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Zilong Zhou ◽  
Jing Zhang ◽  
Xin Cai ◽  
Shanyong Wang ◽  
Xueming Du ◽  
...  
Keyword(s):  
Axial Load ◽  
Fractured Rock ◽  
High Amplitude ◽  
Axial Displacement ◽  
Testing System ◽  
Permeability Evolution ◽  
Permeability Enhancement ◽  
Axial Forces ◽  
Dynamic Forces ◽  
Load Conditions

Permeability experiments on saw-cut fractured rock subjected to cyclic axial load conditions were conducted on the MTS815 rock mechanics testing system. The influence of the frequency and amplitude of cyclic axial forces on axial displacement and permeability evolution of fractured rock was experimentally investigated. Results show that the increasing frequency under the same amplitude of axial load leads to a reduction in axial displacement, but a drop followed by an increase in permeability, while the permeability values oscillated sharply under high amplitude of cyclic loads, which can be attributed to the production of gouge materials. Besides, the increase in axial displacement roughly contributed to the permeability reduction, and excessive amplitude of cyclic load posed limited boost to the permeability enhancement. By comparing with the quasistatic function, we found that it did not completely correspond to the trend of the permeability evolution subjected to cyclic axial forces, and sensitivity coefficients evolving with frequency and amplitude should be considered. A new function of the permeability evolution subjected to the amplitude and frequency of cyclic axial forces was derived and verified by the experimental data. This study suggests that small amplitude and high frequency of dynamic forces have the potential for enhancing the permeability of fracture and triggering the disaster of fractured rock.

SEISMIC SOIL–FOUNDATION–STRUCTURE INTERACTION ANALYSIS OF DEEPLY EMBEDDED VENTILATION STACK

2012 ◽  
Vol 06 (01) ◽  
pp. 1250003
Author(s):  
V. JAYA ◽  
G. R. DODAGOUDAR ◽  
A. BOOMINATHAN
Keyword(s):  
Seismic Response ◽  
Interaction Analysis ◽  
Strong Dependence ◽  
Velocity Ratio ◽  
Relative Displacement ◽  
Response Analysis ◽  
Structure Interaction ◽  
Soil Foundation ◽  
A Site ◽  
Foundation Structure

In this paper, the seismic response analysis of deeply embedded ventilation stack is addressed by considering the effects of soil–foundation–structure interaction (SFSI). Seismic SFSI analysis of the stack subjected to a site-specific design ground motion is carried out using finite element method. A parametric sensitivity analysis is made to investigate the effect of embedment and shear wave velocity ratio of the subsurface profile on the seismic response of the stack. The first series of the SFSI analysis is carried out for the stack with surface footing using computer program SASSI 2000. The second set of analysis incorporates the effect of embedment on the seismic response of the stack. The flexible volume substructure method is used to analyze the seismic SFSI effects. It has been found that the seismic response at the various levels of the stack shows a strong dependence on stiffness of the subsurface profile and the depth of embedment. The spectral acceleration and relative displacement at the top of the stack decrease with increase in embedment ratio and these are the important parameters to be given a due consideration during design process of the stack structures.

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