Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2007 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending ◽  
The Difference

In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned wall elbow, because the life of piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: Computational Approach

2007 ◽  
Author(s):  
Satoshi Tsunoi ◽  
Akira Mikami ◽  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Analytical Model ◽  
Failure Modes ◽  
Experimental Investigations ◽  
Seismic Load ◽  
Piping System ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Seismic Loadings ◽  
Local Wall Thinning

The authors have proposed an analytical model by which they can simulate the dynamic and failure behaviors of piping systems with local wall thinning against seismic loadings. In the previous paper [13], the authors have carried out a series of experimental investigations about dynamic and failure behaviors of the piping system with fully circumferential 50% wall thinning at an elbow or two elbows. In this paper these experiments have been simulated by using the above proposed analytical model and investigated to what extent they can catch the experimental behaviors by simulations.

Investigation of the Seismic Safety Capacity of Aged Piping System: Shake Table Test on Piping Systems With Wall Thinning by E-Defense

2011 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Yuji Sato ◽  
Hajime Takada ◽  
Koji Takahashi ◽  
...  
Keyword(s):  
System Model ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Seismic Safety ◽  
System Models ◽  
Primary Stress ◽  
Wall Thinning ◽  
Piping Systems

In order to investigate the seismic safety capacity of the piping system with local wall thinning, shake table tests on 3-D piping system models were conducted using E-Defense. Two piping system models which were the same in appearance and different in degradation condition were arranged on the shake table of E-Defense. One of the models was put into degradation condition of about 50% wall thinning at four elbows and one tee. Modified seismic motions were applied to these models at the same time. As a result, the piping system model with wall thinning did not fail for the primary stress limit level of sound piping system model, though a ratchet deformation was observed on the thinned wall tee. The model with wall thinning finally failed at the thinned wall tee by over five times larger excitation than the limit level. From the experiment, it was found that the life of the piping system with wall thinning would be reduced compared with that of the piping system without wall thinning, but it was also found that the degraded piping system still had a certain seismic margin until the piping system failed by the seismic load.

Tri-Axial Shake Table Test on the Thinned Wall Piping Model and Damage Detection Before Failure

2010 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Yuji Sato ◽  
Hajime Takada ◽  
Koji Takahashi
Keyword(s):  
Ultrasonic Inspection ◽  
Three Dimensional ◽  
Dominant Frequency ◽  
Shake Table Test ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems

In order to investigate the influence of degradation on dynamic behavior of piping systems and clarify the failure mode of piping systems with local wall thinning, tri-axial shake table tests using three-dimensional piping system models were conducted. The degradation used in this study was wall thinning at elbows and a tee, which was considered to be caused in piping systems due to the effects of aging. The test results show that the dominant frequency and the maximum response acceleration would be reduced due to the existence of wall thinning. Nondestructive inspections such as ultrasonic inspection tests and penetrant inspection tests were applied in the interval of the shake table test in order to detect the damage caused by the repeated shaking. As a result, nondestructive inspection methods would be useful for detecting the damage before the failure caused by the seismic load.

Failure Behavior of Elbows With Local Wall Thinning Under Cyclic Load

2004 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Failure Modes ◽  
Seismic Load ◽  
Failure Behavior ◽  
Cyclic Bending ◽  
Wall Thinning ◽  
Bending Load ◽  
Piping Systems ◽  
Out Of Plane ◽  
Effects Of Aging ◽  
Local Wall Thinning

Pressurized piping systems used in nuclear power plants are supposed to be degraded by the effects of aging. Local wall thinning is one of the defects considered to be caused in piping systems due to the effects of aging, but the failure behavior of thinned wall pipes under seismic load is still not clear. Therefore an experimental and analytical study to clarify the failure behavior of thinned wall pipes is being conducted. In this paper, the experimental results of locally thinned wall elbows under cyclic bending load are described. Displacement-controlled cyclic bending tests were conducted on elbows with local wall thinning. The test models were pressurized to 10MPa with room temperature water and were subjected to in-plane or/and out-of-plane cyclic bending load until their failures. From the tests, the failure modes of the thinned wall elbows were found to be fatigue failure at the flank of the elbow, or fatigue and buckling failure accompanied with ratchet deformation. It was also found that the life of the thinned wall elbow subjected to out-of-plane bending were extremely lower than that of the elbow without wall thinning. The failure modes and fatigue lives of elbows seemed to be affected by a ratchet phenomenon.

Effect of Local Wall Thinning on the Dynamic Behavior of Piping Systems

2005 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Behavior ◽  
Piping System ◽  
Test Model ◽  
System Models ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending ◽  
Local Wall Thinning

In order to investigate the influence of degradation on dynamic behavior and the failure mode of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. The degradation considered in this study was wall thinning, which would be caused in piping systems due to the effects of aging. The degradation condition induced in the piping system model was 50% full circumferential wall thinning at an elbow. The test model was designed to cause out-of-plane bending moment to the thinned-wall elbow by excitation tests. The model without wall thinning was also used in the excitation test to compare the behavior of the piping system models. These models were excited under same input acceleration until fatigue cracks penetrated or an excessive deformation occurred to the models. Through these tests, the vibration characteristic and the process to failure of degraded piping models were obtained for the out-of-plane bending model. This paper describes the dynamic response and failure behavior of piping systems with wall thinning based on the test results.

Failure Analysis of Piping Systems With Thinned Elbows on Tri-Axial Shake Table Tests

2011 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Izumi Nakamura ◽  
Akihito Otani
Keyword(s):  
Plastic Strain ◽  
Failure Analysis ◽  
Seismic Loading ◽  
Fracture Analysis ◽  
Piping System ◽  
Shake Table ◽  
Loading History ◽  
Damage Factor ◽  
Shake Table Tests ◽  
Piping Systems

This paper presents a computational failure analysis of piping systems with and without thinned elbows on tri-axial shake table tests. In a previous experimental study, two piping models, a sound piping system and a degraded piping system with thinned elbows, were assessed. The sound piping system was found to failed at the elbow flank due to in-plane cyclic bending, whereas the degraded system failed at the end of the elbow due to excessive pipe ovalization. In the present study, finite element (FE) models of elbows were developed in order to carry out fracture analysis. The measured displacements of seismic motions were used as the boundary conditions for FE models. In the sound piping system, plastic strain concentrated at the flank of the elbow due to in-plane bending. The cumulative damage factor was calculated from the fatigue curve and Miner’s rule. The effect of ratcheting was also considered. In the failed elbow, the calculated cumulative damage factor showed good agreement with experimental results. On the other hand, for the fracture analysis of the thinned elbow, the entire seismic loading history on the tri-axial shake table was considered, since the effect of pipe ovalization depends on loading history. The ovalization occurred at the elbow due to cumulative seismic loading. Consequently, the principal plastic strain began to concentrate at the end of the elbow. These FE results offer quantitative explanation for the observed failure modes in the degraded piping system.

Failure Analysis of Piping Systems With Thinned Elbows on Tri-Axial Shake Table Tests

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Tadahiro Shibutani ◽  
Izumi Nakamura ◽  
Akihito Otani
Keyword(s):  
Plastic Strain ◽  
Failure Analysis ◽  
Seismic Loading ◽  
Fracture Analysis ◽  
Piping System ◽  
Shake Table ◽  
Loading History ◽  
Damage Factor ◽  
Shake Table Tests ◽  
Piping Systems

This paper presents a computational failure analysis of piping systems with and without thinned elbows on tri-axial shake table tests. In a previous experimental study, two piping models, a sound piping system and a degraded piping system with thinned elbows, were assessed. The sound piping system was found to fail at the elbow flank due to in-plane cyclic bending, whereas the degraded system failed at the end of the elbow due to excessive pipe ovalization. In the present study, finite element (FE) models of elbows were developed in order to carry out fracture analysis. The measured displacements of seismic motions were used as the boundary conditions for FE models. In the sound piping system, plastic strain concentrated at the flank of the elbow due to in-plane bending. The cumulative damage factor was calculated from the fatigue curve and Miner's rule. The effect of ratcheting was also considered. In the failed elbow, the calculated cumulative damage factor showed good agreement with experimental results. On the other hand, for the fracture analysis of the thinned elbow, the entire seismic loading history on the tri-axial shake table was considered, since the effect of pipe ovalization depends on loading history. The ovalization occurred at the elbow due to cumulative seismic loading. Consequently, the principal plastic strain began to concentrate at the end of the elbow. These FE results offer quantitative explanation for the observed failure modes in the degraded piping system.

Fatigue-Ratcheting Behavior of 6 in Pressurized Carbon Steel Piping Systems Under Seismic Load: Experiments and Analysis

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
A. Ravi Kiran ◽  
G. R. Reddy ◽  
P. N. Dubey ◽  
M. K. Agrawal
Keyword(s):  
Carbon Steel ◽  
Response Spectrum ◽  
Thickness Variation ◽  
Seismic Load ◽  
Frequency Change ◽  
Shake Table Tests ◽  
Numerical Studies ◽  
Piping Systems ◽  
Earthquake Load ◽  
Steel Piping

This article presents the experimental and numerical studies of fatigue-ratcheting in carbon steel piping systems under internal pressure and earthquake load. Shake table tests are carried out on two identical 6 in pressurized piping systems made of carbon steel of grade SA333 Gr 6. Tests are carried out using similar incremental seismic load till failure. Wavelet analysis is carried to evaluate frequency change during testing. The tested piping systems are analyzed using iterative response spectrum (IRS) method, which is based on fatigue-ratcheting and compared with test results. Effect of thickness variation in elbow on strain accumulation is studied. Excitation level for fatigue-ratcheting failure is also evaluated and the details are given in this paper.

Simplified Elasto-Plastic Response Analysis of Piping: Considering In-Plane, Out-of-Plane and the Mixed Bending of Elbow

2006 ◽  
Author(s):  
Akihito Otani ◽  
Syozaburo Toyoda ◽  
Izumi Nakamura ◽  
Hajime Takada
Keyword(s):  
Plastic Deformation ◽  
Seismic Excitation ◽  
Response Analysis ◽  
Plastic Response ◽  
Additional Method ◽  
Damping Effect ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending ◽  
Good Agreement

When piping systems are subjected to extreme seismic excitation, they undergo a plastic deformation that produces a large damping effect via energy dissipation. Based on our studies of the damping effect of the elasto-plastic response of piping, we have presented a simplified method for predicting the elasto-plastic response of piping in PVP conferences over the last several years. The method has taken the plastic deformation of in-plane bending elbows into consideration. The elasto-plastic response predicted by the method resulted in good agreement with piping model excitation tests. In this paper, we report an additional method to consider out-of-plane bending elbow and the mixed bending of in-plane and out-of-plane bending. The simulation results by this method and the comparisons with 3D piping model excitation tests are also reported.

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