Fatigue Failure Evaluation Method and Fragility Curve Using Energy

2015 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita ◽  
Shigeki Okamura
Keyword(s):  
Fatigue Failure ◽  
Seismic Design ◽  
Evaluation Method ◽  
Cumulative Damage ◽  
Fragility Curve ◽  
The Other ◽  
Static Force ◽  
Japanese History ◽  
Long Duration ◽  
Failure Evaluation

In this paper, a fatigue failure evaluation method and a fragility curve using energy are proposed. The energy is one of damage indicating parameters and it can evaluate cumulative damage such as fatigue failure. The authors have already reported qualitative relationships between the energy and fatigue failure in previous papers. Great East Japan Earthquake had some features that are different from others, because it was the largest earthquake in Japanese history. For example, the earthquake had long duration time, and many aftershocks. Therefore structures were damaged by cumulative damage. On the other hand, seismic design and evaluation of mechanical structures are generally based on static force in the elastic region, so cumulative damage is not considered. Therefore damage indicating parameters that can evaluate fatigue failure have been required, and the energy is suitable for the evaluation of fatigue failure. In addition, the seismic probabilistic risk assessment (PRA) has attracted attention in recent years, so this paper deals with the fragility curve based on energy as well.

Fundamental Study on Energy Necessary for Tensile Failure

2016 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita
Keyword(s):  
Fatigue Failure ◽  
Seismic Design ◽  
Tensile Tests ◽  
Cumulative Damage ◽  
Tensile Failure ◽  
Seismic Events ◽  
Fundamental Study ◽  
Long Time ◽  
The Relationship

Although, a part of damage of mechanical structures by actual seismic events is caused by cumulative damage, their seismic design is generally carried out by using momentary force or stress, because force and stress are calculated easily. Therefore, damage indicating parameters that can evaluate cumulative damage is necessary, and authors have focused on energy as the parameter. The energy can evaluate fatigue failure because the energy is derived from an integral of a product of force and deformation. In our previous paper, vibration and loading experiments were conducted, and the energy necessary for fatigue failure was reported. However the processes to clarify the energy necessary for failure by fatigue experiments take a long time. The processes will be shortened if the energy is clarified by tensile tests. This paper deals with the energy necessary for tensile failure. In this paper, tensile tests were carried out, and energy necessary for tensile failure was derived. The tensile tests were conducted with various tensile speeds. As a result, more energy is needed when tensile speed is slow. This relationship is same as the relationship confirmed by vibration and loading experiments in our previous papers.

Application of Energy Balance Equation to 2 Degree-of-Freedom Model

2012 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita
Keyword(s):  
Energy Balance ◽  
Fatigue Failure ◽  
Balance Equation ◽  
Evaluation Method ◽  
Energy Balance Equation ◽  
Cumulative Damage ◽  
Degree Of Freedom ◽  
Actual Structure ◽  
Single Degree Of Freedom ◽  
Vibration Experiment

Generally seismic design of mechanical structures is based on static force in elastic region. However dynamic cyclic load may causes cumulative damage, and such damage induces fatigue failure on the structures. In addition, evaluation method of soundness after a huge earthquake is also required. Therefore quantitative evaluation of cumulative damage by earthquakes is required. Authors have investigated this issue from the viewpoint of the energy balance equation. The energy balance equation expresses cumulative information of response, so that the energy balance equation is adequate for the evaluation of the influence of cumulative load such as seismic response. Authors have already clarified qualitative relationships between input energy and fatigue failure of simple single-degree-of-freedom system. However, in order to apply energy balance equation on actual structure, expansion of it to multi-degree-of-freedom systems is required. This paper proposes extension method of energy balance equation to multi-degree-of-freedom system. This paper investigates 2-degree-of-freedom model as an example of multi-degree-of-freedom model, and relationship between energy and failure is investigated by vibration experiment.

LONG DURATION ECHOES FROM AURORA, METEORS, AND IONOSPHERIC BACK-SCATTER

1953 ◽  
Vol 31 (2) ◽  
pp. 171-181 ◽  
Author(s):  
D. W. R. McKinley ◽  
Peter M. Millman
Keyword(s):  
Long Range ◽  
High Frequency ◽  
The Other ◽  
Very High Frequency ◽  
Long Duration ◽  
E Region ◽  
Very High ◽  
Visual Observations

In the course of the Ottawa meteor program some unusual echoes have been detected on 33 Mc. Echoes from the aurora are discussed and correlated with visual observations. Two mechanisms of radio reflections from the aurora have been proposed but the data here presented are insufficient to favor one over the other. On Aug. 4, 1948, six extremely long duration meteor echoes were observed which may have been due to abnormal ionospheric conditions. From time to time since August, 1948, a weak semipermanent echo has been recorded, usually appearing at a range of about 80 km., and enduring up to an hour. It is suggested that this echo is due to back-scatter from the same sources in the lower E-region that are presumed to be responsible for long-range very high frequency propagation.

Evaluation Method for Seismic Fatigue Damage of Plant Pipeline

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Fumio Inada ◽  
Michiya Sakai ◽  
Ryo Morita ◽  
Ichiro Tamura ◽  
Shin-ichi Matsuura ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Nuclear Power ◽  
Power Plants ◽  
Evaluation Method ◽  
Response Spectrum ◽  
Damage Mechanism ◽  
Peak Frequency ◽  
Cumulative Damage ◽  
Cumulative Absolute Velocity ◽  
Seismic Index

Although acceleration and cumulative absolute velocity (CAV) are used as seismic indexes, their relationship with the damage mechanism is not yet understood. In this paper, a simplified evaluation method for seismic fatigue damage, which can be used as a seismic index for screening, is derived from the stress amplitude obtained from CAV for one cycle in accordance with the velocity criterion in ASME Operation and Maintenance of Nuclear Power Plants 2012, and the linear cumulative damage due to fatigue can be obtained from the linear cumulative damage rule. To verify the performance of the method, the vibration response of a cantilever pipe is calculated for four earthquake waves, and the cumulative fatigue damage is evaluated using the rain flow method. The result is in good agreement with the value obtained by the method based on the relative response. When the response spectrum obtained by the evaluation method is considered, the value obtained by the evaluation method has a peak at the peak frequency of the ground motion, and the value decreases with increasing natural frequency above the peak frequency. A higher peak frequency of the base leads to a higher value obtained by the evaluation method.

scholarly journals Intramural optical mapping of Vm and Cai2+ during long-duration ventricular fibrillation in canine hearts

2012 ◽  
Vol 302 (6) ◽  
pp. H1294-H1305 ◽  
Author(s):  
Wei Kong ◽  
Raymond E. Ideker ◽  
Vladimir G. Fast
Keyword(s):  
Ventricular Fibrillation ◽  
Action Potential ◽  
Short Duration ◽  
Action Potential Duration ◽  
Cycle Length ◽  
The Other ◽  
Membrane Voltage ◽  
Long Duration ◽  
Intracellular Ca ◽  
Rapid Pacing

Intramural gradients of intracellular Ca2+ (Cai2+) Cai2+ handling, Cai2+ oscillations, and Cai2+ transient (CaT) alternans may be important in long-duration ventricular fibrillation (LDVF). However, previous studies of Cai2+ handling have been limited to recordings from the heart surface during short-duration ventricular fibrillation. To examine whether abnormalities of intramural Cai2+ handling contribute to LDVF, we measured membrane voltage ( Vm) and Cai2+ during pacing and LDVF in six perfused canine hearts using five eight-fiber optrodes. Measurements were grouped into epicardial, midwall, and endocardial layers. We found that during pacing at 350-ms cycle length, CaT duration was slightly longer (by ≃10%) in endocardial layers than in epicardial layers, whereas action potential duration (APD) exhibited no difference. Rapid pacing at 150-ms cycle length caused alternans in both APD (APD-ALT) and CaT amplitude (CaA-ALT) without significant transmural differences. For 93% of optrode recordings, CaA-ALT was transmurally concordant, whereas APD-ALT was either concordant (36%) or discordant (54%), suggesting that APD-ALT was not caused by CaA-ALT. During LDVF, Vm and Cai2+ progressively desynchronized when not every action potential was followed by a CaT. Such desynchronization developed faster in the epicardium than in the other layers. In addition, CaT duration strongly increased (by ∼240% at 5 min of LDVF), whereas APD shortened (by ∼17%). CaT rises always followed Vm upstrokes during pacing and LDVF. In conclusion, the fact that Vm upstrokes always preceded CaTs indicates that spontaneous Cai2+ oscillations in the working myocardium were not likely the reason for LDVF maintenance. Strong Vm-Cai2+ desynchronization and the occurrence of long CaTs during LDVF indicate severely impaired Cai2+ handling and may potentially contribute to LDVF maintenance.

Yield Point Spectra for Seismic Design and Rehabilitation

2000 ◽  
Vol 16 (2) ◽  
pp. 317-335 ◽  
Author(s):  
Mark Aschheim ◽  
Edgar F. Black
Keyword(s):  
Yield Point ◽  
Seismic Design ◽  
Ground Motions ◽  
Existing Structures ◽  
Intuitive Appeal ◽  
Forward Directivity ◽  
Capacity Spectrum ◽  
Long Duration ◽  
Nonlinear Static ◽  
Strength And Stiffness

A new spectral representation of seismic demand is described for use in the seismic design of new structures and in the evaluation and rehabilitation of existing structures. Yield Point Spectra (YPS) retain the intuitive appeal of the Capacity Spectrum Method (Freeman 1978) and join the Nonlinear Static Procedures of FEMA 273/274 (1997) and ATC 40 (1996) for use in estimating displacement demands. YPS also may be used to establish admissible combinations of strength and stiffness for the design of new structures to limit system ductility and drift to arbitrary values. Graphical procedures allow admissible design regions to be established to satisfy multiple performance objectives. YPS computed for 15 ground motions classified as Short Duration, Long Duration, or as containing near-fault Forward Directivity pulses are presented for bilinear and stiffness-degrading hysteretic models.

The Research on Hysteretic Energy in the Equivalent System Schemes between Multi Degree of Freedom System and Single Degree of Freedom System

2012 ◽  
Vol 166-169 ◽  
pp. 2177-2181
Author(s):  
Ming Qiang Sheng ◽  
Ying Liu
Keyword(s):  
Seismic Design ◽  
Seismic Waves ◽  
Good Alternative ◽  
Cumulative Damage ◽  
Degree Of Freedom ◽  
Equivalent System ◽  
Single Degree Of Freedom ◽  
Hysteretic Energy ◽  
Single Degree ◽  
Comparison And Analysis

The cumulative damage produced by severe earthquake is significant to the structural dilapidation and collapse. Most design methods based on force or displacement can’t reflect the effect of cumulative damage. Energy-based seismic design is known as a good alternative design. At present the research on the hysteretic energy of single-degree of freedom system(SDOF) is abundant, but real buildings can only be simplified as multi-degree of freedom systems(MDOF) mostly. Therefore how to acquire suitable equivalent single-degree of freedom system(ESDOF) is a key program. In this paper 12 equivalent system schemes(ESS) have been put forward, then the ratio of hysteretic energy(RH) of 6-floors framework was calculated with 30 typical seismic waves. Based on the comparison and analysis between calculations of 3 typical ESS, by the way of envelope fitting, the expression of RH related to earthquake characteristic value a/v was established.

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