Marginal Hilbert spectrum and instantaneous phase difference as total damage indicators in bridges under operational traffic loads

Flow-induced vibrations (FIV) are conventionally destructive and should be suppressed. Since 2006, the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan has been studying FIV of multiple cylinders to enhance their response for harnessing hydrokinetic power from ocean, river, and tidal currents. Interactions between multiple cylinders in FIV enable high power-to-volume ratio in a converter consisting of multiple oscillators. This paper investigates experimentally the relation between oscillation patterns and frequency response of two cylinders in tandem. All experiments are conducted in the recirculating channel of the MRELab for 30,000 < Re < 120,000. Phase analysis reveals three dominant patterns of oscillation of two tandem cylinders by calculating the instantaneous phase difference between the two cylinders. This phase difference characterizes each major pattern. Pattern A is characterized by small lead or lag of one cylinder over the other. In pattern B, there is nearly 180 deg out of phase oscillations between the cylinders. In pattern C, the instantaneous phase difference changes continuously from −180 deg to +180 deg. Using frequency spectra and amplitude response, oscillation characteristics of each cylinder are revealed in vortex-induced vibration (VIV) and galloping. Pattern A occurs mostly in galloping when the first cylinder has higher stiffness. Pattern B occurs seldom and typically in the initial VIV branch and transition from VIV to galloping. Pattern C occurs in the upper and lower VIV branches; and in galloping when the lead cylinder has lower stiffness.

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Instantaneous phase difference analysis between thoracic and abdominal movement signals based on complementary ensemble empirical mode decomposition

BioMedical Engineering OnLine ◽

10.1186/s12938-016-0233-7 ◽

2016 ◽

Vol 15 (1) ◽

Cited By ~ 1

Author(s):

Ya-Chen Chen ◽

Tzu-Chien Hsiao

Keyword(s):

Empirical Mode Decomposition ◽

Phase Difference ◽

Ensemble Empirical Mode Decomposition ◽

Difference Analysis ◽

Instantaneous Phase ◽

Mode Decomposition ◽

Thoracic And Abdominal ◽

Abdominal Movement

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Detection of Karst Cavity Beneath Cast-in-place Pile Using Instantaneous Phase Difference of Two Receiver Recordings

Geophysics ◽

10.1190/geo2020-0082.1 ◽

2020 ◽

pp. 1-50

Author(s):

Liu Liu ◽

Zhenming Shi ◽

Georgios Tsoflias ◽

Ming Peng ◽

Chengcheng Liu ◽

...

Keyword(s):

Surface Waves ◽

Phase Difference ◽

Analysis Method ◽

Dominant Wavelength ◽

P Waves ◽

Instantaneous Phase ◽

Numerical Tests ◽

Field Investigations ◽

The Stability

Karst cavities beneath bored cast in situ piles are hazardous to the stability of infrastructure projects. Therefore, it is important to detect karst cavities during the construction of piles. Downward looking sonar deployed at the bottom of a pile hole can be used to detect cavities, however, interference of multiple reflected surface waves from the walls of the pile hole masks the weak cavity reflections. We introduce a sonar method that exploits the instantaneous phase difference between signals recorded at two receivers to detect karst cavities beneath piles. The receiver separation is set to half the dominant wavelength of surface waves propagating along the pile hole. We define Instantaneous Phase Difference Intensity (IPDI) as an index that measures the similarity of instantaneous phase between the signals at the two receivers. Higher IPDI signifies that the two signals have similar instantaneous phase at that time, which implies the arrival of a reflection from a cavity. Reflected surface wave arrivals exhibit low IPDI by design of the receiver geometry. Thus, the first break of reflected P-waves from the roof and floor of a cavity can be identified. We evaluate the effectiveness of the IPDI based analysis method using numerical tests simulating varying depth, azimuth and size of karst cavities. A prototype using the IPDI analysis demonstrates the application of the new pile hole sonar method at two field investigations. Advance drilling, borehole optical image logs and cross-hole tomography verify the IPDI detection results. We conclude that the two-receiver sonar instrumentation along with the IPDI analysis are effective for detecting cavities beneath piles.

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A Hilbert–Huang Transform-Based Adaptive Fault Detection and Classification Method for Microgrids

Energies ◽

10.3390/en14165040 ◽

2021 ◽

Vol 14 (16) ◽

pp. 5040

Author(s):

Yijin Li ◽

Jianhua Lin ◽

Geng Niu ◽

Ming Wu ◽

Xuteng Wei

Keyword(s):

Fault Detection ◽

Phase Difference ◽

High Frequency ◽

Frequency Component ◽

High Frequency Component ◽

Hilbert Huang Transform ◽

Instantaneous Phase ◽

Fault Type ◽

Fault Detection And Classification ◽

Fault Characteristic

Fault detection in microgrids is of great significance for power systems’ safety and stability. Due to the high penetration of distributed generations, fault characteristics become different from those of traditional fault detection. Thus, we propose a new fault detection and classification method for microgrids. Only current information is needed for the method. Hilbert–Huang Transform and sliding window strategy are used in fault characteristic extraction. The instantaneous phase difference of current high-frequency component is obtained as the fault characteristic. A self-adaptive threshold is set to increase the detection sensitivity. A fault can be detected by comparing the fault characteristic and the threshold. Furthermore, the fault type is identified by the utilization of zero-sequence current. Simulations for both section and system have been completed. The instantaneous phase difference of the current high-frequency component is an effective fault characteristic for detecting ten kinds of faults. Using the proposed method, the maximum fault detection time is 13.8 ms and the maximum fault type identification time is 14.8 ms. No misjudgement happens under non-fault disturbance conditions. The simulations indicate that the proposed method can achieve fault detection and classification rapidly, accurately, and reliably.

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Repeatability study of seismic source signatures

Geophysics ◽

10.1190/1.1487123 ◽

2001 ◽

Vol 66 (6) ◽

pp. 1811-1817 ◽

Cited By ~ 19

Author(s):

Bibi C. Aritman

Keyword(s):

Phase Difference ◽

Seismic Source ◽

Seismic Survey ◽

Surface Source ◽

Near Surface ◽

Seismic Surveys ◽

Instantaneous Phase ◽

Reservoir Monitoring ◽

The Difference

This study discusses the repeatability of source signature using the instantaneous phase, as derived from the complex trace attributes. The study is part of a very large 2‐D seismic survey using sources of vibroseis and surface dynamite. The field procedure consisted of recording the production record, retaining the positions, then repeat‐recording the same shake or shot. The instantaneous phase was found to be the best measure for the difference between the first and the repeat records. In addition to the instantaneous phase, other analyses were used to evaluate changes in source signature. Results were tabulated for statistical comparisons and graded for quality. Excluding erroneous cases, the remainder of poor repeatabilities were studied. The analyses of near‐offset data seem to indicate that nonrepeatability of source signature relates mostly to changes in absorption and cohesion induced by elastic saturation at the near surface. In general, by time shifting and phase rotating the repeat record, the difference in instantaneous phase tends to diminish. The new idea of using instantaneous phase difference plots to evaluate repeatability offers improved evaluation of source signatures and can also be used to detect time‐lapsed changes in reservoir monitoring. By evaluating repeatability and avoiding elastic saturation near the surface, source signatures can be made more consistent, thus increasing the resolution of stacked data for 2‐D, 3‐D, and 4‐D seismic surveys.

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Weigh-in-Motion-Based Fatigue Damage Assessment

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120919758 ◽

2020 ◽

Vol 2674 (8) ◽

pp. 710-719

Author(s):

Olga Iatsko ◽

Anjan Ramesh Babu ◽

J. Michael Stallings ◽

Andrzej S. Nowak

Keyword(s):

Fatigue Damage ◽

The State ◽

Bottom Flange ◽

Steel Bridge ◽

Traffic Data ◽

Traffic Loads ◽

Weigh In Motion ◽

Fatigue Damage Accumulation ◽

Total Damage ◽

Combined Data

Weigh-in-motion (WIM) data provide an excellent opportunity to study the effects of actual traffic loads on bridges. Here procedures are presented for using WIM data to quantify the fatigue damage accumulated in steel bridges. These procedures allow comparisons of the impacts of truck traffic on various routes beyond simple comparisons of the numbers and gross vehicles weights of trucks in the traffic streams. The fatigue damage accumulation procedures are demonstrated using WIM traffic data collected in the state of Alabama. The results of the analysis show that approximately 20% of trucks are overloaded, that is, permit loads and illegal loads, and those trucks create more than 50% of the total damage based on the combined data from all the WIM locations in the state. The contribution of overloaded trucks to the total fatigue damage varies so that their contribution is less significant along some routes. A typical steel bridge with bottom flange coverplates was evaluated using the WIM data from 1 year for a heavily traveled route. This analysis shows that the fatigue life of the bridge was consumed at an annual rate consistent with a mean life of 100 years. These procedures have applications in planning weight limit enforcement, budgeting, and maintenance, and they have the potential for future use in planning inspection intervals.

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