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.

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: 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.

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.

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 on Failure Behavior of Two-Elbow Piping System Models Made of the Simulation Material Under Excessive Seismic Loads

2020 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Failure Modes ◽  
Shaking Table ◽  
System Model ◽  
Failure Behavior ◽  
Piping System ◽  
Seismic Loads ◽  
Sinusoidal Wave ◽  
Additional Mass ◽  
System Models ◽  
Piping Systems

Abstract To investigate the failure behavior of piping systems under excessive seismic loads, shaking table tests on piping system models made of a simulation material have been executed. The simulation material adopted in the experiment was lead-antimony (Pb-Sb) alloy. The piping system model was composed of two elbows made of Pb-Sb alloy, one additional mass, and two fixed anchors. Input motions were sinusoidal wave. The failure modes of the piping system were examined by varying the additional mass and frequency of the input sinusoidal wave. Through the excitation tests, the failure mode which was named as “ratchet and subsequent collapse” was obtained successfully. The result which was classified as “no failure after 500 cycles” was also obtained. It was found that the occurrence of the failure depended on the ratio of the input frequency to the specimen’s natural frequency, and the ratio of additional mass weight to the limit mass weight. Though the effect of higher modes on the failure behavior was necessary to be more investigated, it seemed that the tendency of dominant failure behavior was similar to that of the single-elbow specimen investigated in the previous study. Moreover, it was confirmed that the experimental approach to use a simulation material was applicable for piping system model with multiple elbows.

0111 Shake table tests for piping system models with an EDM crack

2007 ◽  
Vol 2007.5 (0) ◽  
pp. 21-22
Author(s):  
Izumi NAKAMURA ◽  
Akihito OTANI ◽  
Masaki SHIRATORI
Keyword(s):  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
System Models

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.

Seismic Safety Capacity of a Piping System With Pipe Supports Based on the Shake Table Test

2013 ◽  
Author(s):  
Izumi Nakamura
Keyword(s):  
Failure Mode ◽  
The Body ◽  
Shake Table Test ◽  
System Model ◽  
Piping System ◽  
Shake Table ◽  
Seismic Capacity ◽  
Seismic Safety ◽  
Response Characteristics ◽  
Input Acceleration

It is well known that the seismic safety capacity of a piping system itself is considerably high compared to the design limitation from the various preceding studies. But most of the preceding studies focused on the seismic capacity of a piping system without other elements as supports, and the safety capacity may be reduced if the failure at supports, nozzles, or flange connections were precedent to the failure at the body of pipe. Therefore the shake table test on the piping system model with supports was conducted. The piping system model used in the shake table test had three supports, a tank, a valve, and flange connections. Excitations were conducted at several input acceleration intensity, and the response characteristics and the failure mode of the piping system were obtained. The failure mode of the piping system model was the broken damage at a pipe support, and after that the leakage at a flange connection occurred. Though the piping system was damaged at pipe supports, it was shown that the piping system model had a certain seismic capacity compared to the design limitation.

Hybrid Seismic Response Evaluation Method for Wall Thinning Piping System

2013 ◽  
Author(s):  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Fumio Inada
Keyword(s):  
Seismic Response ◽  
Evaluation Method ◽  
Low Cycle Fatigue ◽  
Shaking Table ◽  
Piping System ◽  
Shaking Table Tests ◽  
Seismic Safety ◽  
Pipe Model ◽  
Wall Thinning ◽  
Piping Systems

Pipe wall thinning is a one of the major degradation mechanisms in aged nuclear power plants (NPPs). In Japan, the seismic safety of wall thinning piping system during earthquake must be evaluated in aged NPPs. Seismic safety of piping systems with wall thinning had been investigated by other researchers using shaking table tests of reduced scale and numerical analyses. However, there exist the limitations such as the scale effect of pipe model for shaking table tests and the limit of the evaluation for numerical analysis concerning the criteria of pipe integrity. By the way, elbow can be one of the most important elements to evaluate the seismic safety of piping system. So, in order to evaluate seismic safety of piping systems with wall thinning elbow, hybrid tests have been conducted, in which the seismic response of the whole piping system is treated as a numerical model, and the real piping is used only for the element on which the transformation and damage locally concentrated. The through-wall crack only occurred in the case of a uniform thinning model although cracks didn’t penetrate in the non thinning model and the local thinning model. In the experimental condition, the failure mode of wall thinning elbow under seismic loadings had been low cycle fatigue, and effectiveness of this evaluation method has been demonstrated.

Sign in / Sign up

Export Citation Format

Share Document