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.

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.

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.

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.

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

Development of Elastic-Plastic Constitutive Models for the Evaluation of Nuclear Piping Systems Under Severe Cyclic Loading

2012 ◽  
Author(s):  
Yukio Takahashi ◽  
Yoshihiko Tanaka
Keyword(s):  
Cyclic Loading ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Seismic Loading ◽  
Piping System ◽  
Elastic Plastic ◽  
Piping Systems

It is essential to predict the behavior of nuclear piping system under seismic loading to evaluate the structural integrity of nuclear power plants. Relatively large stress cycles may be applied to the piping systems under severe seismic loading and plastic deformation may occur cyclically in some portion of the systems. Accurate description of inelastic deformation under cyclic loading is indispensable for the precise estimation of strain cycles and accumulation potentially leading to the failure due to fatigue-ratcheting interaction. Elastic-plastic constitutive models based on the nonlinear kinematic hardening rule proposed by Ohno and Wang were developed for type 316 austenitic stainless steel and carbon steel JIS STPT410 (similar to ASTM A106 Gr.B), both of which are used in piping systems in nuclear power plants. Different deformation characteristics under cyclic loading in terms of memory of prior hardening were observed on these two materials and they were reflected in the modeling. Results of simulations under various loading conditions were compared with the test data to demonstrate the high capability of the constitutive models.

Evaluation of Inelastic Seismic Response of a Piping System Using a Modified Iterative Response Spectrum Method

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
A. Ravikiran ◽  
P. N. Dubey ◽  
M. K. Agrawal ◽  
G. R. Reddy ◽  
K. K. Vaze
Keyword(s):  
Failure Mode ◽  
Seismic Event ◽  
Response Spectrum ◽  
Experimental Results ◽  
Piping System ◽  
Strain Accumulation ◽  
Shake Table Tests ◽  
Accumulated Strain ◽  
Piping Systems ◽  
Inelastic Seismic Response

In pressurized piping systems, strain accumulation may take place due to cyclic loading during a seismic event. This incremental plastic deformation called ratcheting may lead to failure of the piping systems. There is no numerical method available to evaluate this accumulated strain in the piping system using response spectrum as input. In the literature, incremental hinge technique is available to predict the failure level conservatively by considering static collapse as the failure mode. However, it is observed from shake table tests that failure in the piping components, especially in elbows, is due to ratcheting. Considering this failure mode and design input as a response spectrum, a modified incremental hinge technique is developed and validated with experimental results. The strain predicted by this analysis closely matches with that of experimental results which are available up to an excitation of 0.75 g ZPA (zero period acceleration). In the experiment, the pressure boundary rupture occurred at 2 g ZPA, while the analysis predicts the failure of the piping system at 2.37 g ZPA. Details of these investigations are presented in the paper.

Dynamic Response of Coupled Tanks and Piping Systems Under Seismic Loading

2015 ◽  
Author(s):  
Oreste S. Bursi ◽  
Giuseppe Abbiati ◽  
Luca Caracoglia ◽  
Vincenzo La Salandra ◽  
Rocco Di Filippo ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Boundary Conditions ◽  
Seismic Loading ◽  
Coupled System ◽  
Coupled Systems ◽  
Piping System ◽  
Axial Loads ◽  
Industrial Plants ◽  
Piping Systems ◽  
Uncertain Boundary

Dynamic analysis is an integral part of seismic risk assessment of industrial plants. Such analysis often neglects actual boundary conditions or proper coupling between structures of coupled systems, which introduces uncertainty into the system and may lead to erroneous results, e.g., an incorrect fragility curve, in comparison with the actual behaviour of the analyzed structure. Hence, it is important to study the effect of uncertainties on the dynamic characteristics of a system, when coupling effects are neglected. Along this line, this paper investigates the effects of uncertain boundary conditions on the dynamic response of coupled tank-piping systems subjected to seismic loading. In particular, to take into account the presence of the tank as boundary condition for the piping system, two sources of uncertainty were considered: the tank aspect ratio and the piping-to-tank attachment height ratio. Moreover, to model the seismic input, a Filtered White Noise (FWN) characterized by a Kanai-Tajimi spectrum was used. Finally, to study the dynamic interaction of a set of coupled tank-piping systems, the non-intrusive stochastic collocation (SC) technique was applied. It allowed for calculating surface responses of stresses and axial loads of a pair of components of the coupled system with a reduced number of deterministic numerical simulations.

Experimental and Numerical Studies of Ratcheting in a Pressurized Piping System Under Seismic Load

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
A. Ravikiran ◽  
P. N. Dubey ◽  
M. K. Agrawal ◽  
G. R. Reddy ◽  
R. K. Singh ◽  
...  
Keyword(s):  
Comprehensive Evaluation ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Seismic Loading ◽  
Seismic Load ◽  
Piping System ◽  
Inelastic Response ◽  
Design Procedures ◽  
Numerical Studies ◽  
Piping Systems

Rational seismic design procedures necessitate comprehensive evaluation of nuclear piping systems under large amplitude seismic loads. This comprehensive assessment requires accurate prediction of inelastic response of piping system till failure to ensure adequate margins for unexpected beyond design basis events. The present paper describes the details of experimental and numerical studies of inelastic response of pressurized piping system under seismic loading. Shake table test has been carried out on a three-dimensional stainless steel piping system under internal pressure and seismic load. The amplitude of base excitation has been increased till failure of the piping system. The tested piping system has been analyzed using iterative response spectrum (IRS) method for various levels of excitation. The comparison of numerical and experimental results is given in the paper.

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