Failure Modes of Piping Systems Under Seismic Loading and Evaluation

2019 ◽  
Author(s):  
Satoru Kai ◽  
Akihito Otani
Keyword(s):  
Plastic Deformation ◽  
Failure Modes ◽  
Seismic Loading ◽  
Response Analysis ◽  
Plastic Collapse ◽  
Stress Evaluation ◽  
Dynamic Reliability ◽  
Primary Stress ◽  
Input Force ◽  
Piping Systems

Abstract Failure modes of piping systems under seismic motions were discussed for several decades if the fatigue failure is dominant or there is some possibility that the plastic collapse could occur. A handful of ratchet-buckling failure observed in Pipe Fittings Dynamic Reliability Program by EPRI was frequently taken up as the evidence of the plastic collapse, and inclusion of seismic response on structures into the Primary stress evaluation for piping systems in the code evaluation was considered to be conventionally justified. Although prevention of the plastic collapse type failure is the purpose of imposing the Primary stress evaluation, the other experimental tests conducted in several countries for decades were unable to represent the plastic collapse of piping components exposed to seismic loading and the discussion was abandoned for a while. However, the drastically increased design seismic motions for nuclear power plants due to several huge earthquake occurred in Japan reminded us of exploring the fact of the plastic collapse and the necessity of the Primary stress evaluation. The load classification concept proposed by the authors introduces 3 conceptual force terms from the equation of motion to clarify the seismic loading from the aspect of the correlation of the said force terms. Based on the finding from the concept that the input force amplitude is to be evaluated for Primary stress, the gross-plastic deformation on a single cantilever with elastic-plastic analyses using multiple of single-cycle sinusoidal forcing functions was compared with the input force term. When the plastic collapse is defined as a gross-plastic deformation, the level of plastic collapse was found to be possibly anticipated with a static force evaluation that can be substitute for the conventional Primary stress evaluation with the dynamic response analysis.

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.

Simplified Elasto-Plastic Response Analysis Method of Piping

2004 ◽  
Author(s):  
Akihito Otani ◽  
Izumi Nakamura ◽  
Hajime Takada
Keyword(s):  
Plastic Deformation ◽  
Damping Ratio ◽  
Fem Analysis ◽  
Simulation Method ◽  
Response Analysis ◽  
Plastic Response ◽  
Dissipation Energy ◽  
Equivalent Damping ◽  
Damping Effect ◽  
Piping Systems

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. Yet the elasto-plastic response of piping calculated by this method resulted in conservative predictions compared with the results of piping model excitation tests. In the proposed method, we calculate the vibration energy of piping and the dissipation energy with plastic deformation by FEM analysis and obtain the equivalent damping ratio as a ratio between the two. The equivalent damping ratio and response are interdependent and can be calculated as a pair of converged values. In this paper we report simulation results from 3D piping model excitation tests as well as the results from 2D piping model tests. The simulation method is a modified and improved version of the method reported earlier. The results obtained by the revised method more closely matched the results of the excitation tests.

Proposal of Use of Mises Criteria for Elastic Analysis in Appendix 9 of ASME Section VIII Division 3

2020 ◽  
Author(s):  
Susumu Terada
Keyword(s):  
Flow Stress ◽  
Plastic Collapse ◽  
Elastic Analysis ◽  
Stress Evaluation ◽  
Stress Theory ◽  
Elastic Plastic ◽  
Primary Stress ◽  
Plastic Analysis ◽  
Section Viii ◽  
Von Mises

Abstract The stress evaluation by elastic analyses for protection against plastic collapse in Appendix 9 is based on maximum shear stress theory (Tresca theory). On the other hand, the stress evaluation by elastic-plastic analysis and design equations by flow stress for design pressure for cylindrical shell and spherical shell in KD-221 is based on distortion energy yield stress theory (von Mises theory). With regard to materials with low and intermediate Sy/Su, in particular the primary stress evaluation based on Tresca stress for elastic analysis in current Div.3 is much more conservative than that based on flow stress equations similar to elastic-plastic analysis from experimental results. In Section VIII Div.2, von Mises yield criterion is used for stress evaluation for elastic analysis because it matches experimental results more closely than Tresca yielding criterion and is also consistent with plasticity algorithms used in elastic-plastic analysis. Therefore in Div.3 von Mises stress should be used for elastic analysis in the same way as in Sec. VIII Div.2. For materials with high Sy/Su, the primary stress evaluation based on von Mises criterion for elastic analysis is less conservative than that based on flow stress equations similar to elastic-plastic analysis because of a difference in design factor of 1.5 for elastic analysis and 1.732 for flow stress equations. Therefore, we propose using von Mises criterion for protection against plastic collapse with design correction factor using Sy/Su in Appendix 9 in order to remove excessive conservativeness for materials with low and intermediate Sy/Su. The validity of this proposal is shown in this paper.

Research Plan and Progress to Realize Fracture Control of Nuclear Components

2019 ◽  
Author(s):  
Naoto Kasahara ◽  
Takashi Wakai ◽  
Izumi Nakamura ◽  
Takuya Sato
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Large Scale ◽  
Failure Modes ◽  
Failure Behavior ◽  
Piping System ◽  
Piping Systems ◽  
Research Plan ◽  
Fracture Control ◽  
Accident Consequence

Abstract For safety improvement after Fukushima daiichi nuclear power plant accident, mitigation of accident consequence for Beyond Design Basis Events (BDBE) has become important. Authors propose application of fracture control concept for mitigation of accident consequence of nuclear plants as follows. In the case of reactor vessels under high temperature and pressure conditions, small cracks from local failure will release internal pressure and can avoid a large scale ductile fracture of general portions. For piping under excessive earthquake, repeated elastic-plastic deformation and ratchet deformation dissipate vibration energy and reduce input energy from floor. They can prevent collapse of piping systems or break of pipe wall. Strength of pipe supports can be designed lower than pipe itself. Controlling the failure of supports would lead to plastic deformation without the break. The ratio of the frequency of seismic loading to the natural frequency of the piping system would also affect the failure behavior of piping systems. This paper describes research plan and progress to realize fracture control of nuclear components. The first step is clarification of actual failure modes and their mechanisms. Next step is development of relative strength evaluation method among failure modes. The third step is proposals of failure control methods. One of example is a vessel under high pressure and high temperature loadings. Another example is pipe under excessive earthquake.

Reduction of First Excursion Probability Due to Plastic Deformation and Absorbed Energy

2004 ◽  
Author(s):  
Shigeru Aoki
Keyword(s):  
Plastic Deformation ◽  
Hysteresis Loop ◽  
Random Process ◽  
Failure Modes ◽  
Seismic Loading ◽  
Theoretical Method ◽  
Equivalent Linearization ◽  
Absorbed Energy ◽  
Nonstationary Random Process ◽  
Excursion Probability

When the system is subjected to excess seismic loading, spring element has hysteresis loop characteristic caused by plastic deformation. Energy is dissipated by hysteresis loop characteristic. Elastic-plastic damper which utilizes energy absorption is practically used. On the other hand, response is nonstationary random process because seismic loading is nonstationary random process. In such a case, reliability of the system should be evaluated in probabilistic manner. Some failure modes are observed. First excursion failure is one of the most important failure modes. First excursion probability, that is, probability of occurrence of first excursion failure, also represents the characteristic of random process. In this paper, the first excursion probability and absorbed energy by hysteresis loop characteristic are obtained from theoretical method. This method is based on equivalent linearization method. Bilinear hysteresis loop characteristic is used as force-deformation relation. It is concluded that the first excursion probability decreases with the increase of absorbed energy.

Failure Behavior of Piping Systems With Wall Thinning Under Seismic Loading

2004 ◽  
Vol 126 (1) ◽  
pp. 85-90 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Three Dimensional ◽  
Seismic Loading ◽  
Shaking Table ◽  
Failure Behavior ◽  
Shaking Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Input Acceleration

Shaking table tests of three-dimensional piping models with degradation were conducted in order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems. The degradation condition induced in the piping models was about 50 percent full circumferential wall thinning at elbows. Four types of models were made for the shaking table tests by varying the location of wall thinning in the piping models. These models were excited under the same input acceleration until the models failed and a leak of pressurized internal water occurred. Through these tests, the change of the vibration characteristics and processes to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and the damage was concentrated on the weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.

Failure Behavior of Piping Systems With Wall Thinning Under Seismic Loading

2002 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Seismic Loading ◽  
Shaking Table ◽  
Failure Behavior ◽  
Vibration Characteristic ◽  
Shaking Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Input Acceleration

In order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems, shaking table tests of 3-D piping models with degradation were conducted. The degradation condition induced in the piping models was about 50% full circumferential wall thinning at an elbow or elbows. By varying the induced parts in the piping model, 4 kinds of models were made for the shaking table tests. These models were excited under the same input acceleration until the models failed and caused leak of pressurized internal water. Through these tests, the change of the vibration characteristic and the process to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and therefore the damage concentrated to a weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.

Dynamic reliability analysis of mechanical system with wear and vibration failure modes

2021 ◽  
Vol 163 ◽  
pp. 104385
Author(s):  
We Wang ◽  
Gang Shen ◽  
Yimin Zhang ◽  
Zhencai Zhu ◽  
Changyou Li ◽  
...  
Keyword(s):  
Mechanical System ◽  
Reliability Analysis ◽  
Failure Modes ◽  
Dynamic Reliability

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.

Simplified Stress Linearization Method, Maintaining Accuracy

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Andrzej T. Strzelczyk ◽  
Mike Stojakovic
Keyword(s):  
Limit Analysis ◽  
Linearization Method ◽  
Finite Element Program ◽  
Stress Evaluation ◽  
Primary Stress ◽  
Stress Classification ◽  
Stress Components ◽  
3D Elements ◽  
Element Program ◽  
Axisymmetric Structure

ASME PVP Code stress linearization is needed for assessment of primary and primary-plus-secondary stresses. The linearization process is not precisely defined by the Code; as a result, it may be interpreted differently by analysts. The most comprehensive research on stress linearization is documented in the work of Hechmer and Hollinger [1998, “3D Stress Criteria Guidelines for Application,” WRC Bulletin 429.] Recently, nonmandatory recommendations on stress linearization have been provided in the Annex [Annex 5.A of Section VIII, Division 2, ASME PVP Code, 2010 ed., “Linearization of Stress Results for Stress Classification.”] In the work of Kalnins [2008, “Stress Classification Lines Straight Through Singularities” Proceedings of PVP2008-PVT, Paper No. PVP2008-61746] some linearization questions are discussed in two examples; the first is a plane-strain problem and the second is an axisymmetric analysis of primary-plus secondary stress at a cylindrical-shell/flat-head juncture. The paper concludes that for the second example, the linearized stresses produced by Abaqus [Abaqus Finite Element Program, Version 6.10-1, 2011, Simulia Inc.] diverge, therefore, these linearized stresses should not be used for stress evaluation. This paper revisits the axisymmetric analysis discussed by Kalnins and attempts to show that the linearization difficulties can be avoided. The paper explains the reason for the divergence; specifically, for axisymmetric models Abaqus inconsistently treats stress components, two stress components are calculated from assumed formulas and all other components are linearized. It is shown that when the axisymmetric structure from Kalnins [2008, “Stress Classification Lines Straight Through Singularities” Proceedings of PVP2008-PVT, Paper No. PVP2008-61746] is modeled with 3D elements, the linearization results are convergent. Furthermore, it is demonstrated that both axisymmetric and 3D modeling, produce the same and correct stress Tresca stress, if the stress is evaluated from all stress components being linearized. The stress evaluation, as discussed by Kalnins, is a primary-plus-secondary-stresses evaluation, for which the limit analysis described by Kalnins [2001, “Guidelines for Sizing of Vessels by Limit Analysis,” WRC Bulletin 464.] cannot be used. This paper shows how the original primary-plus-secondary-stresses problem can be converted into an equivalent primary-stress problem, for which limit analysis can be used; it is further shown how the limit analysis had been used for verification of the linearization results.

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