The OECD-NEA Programme on Metallic Component Margins Under High Seismic Loads (MECOS)

2016 ◽  
Author(s):  
Pierre B. Labbé ◽  
G. R. Reddy ◽  
Cedric Mathon ◽  
François Moreau ◽  
Spyros A. Karamanos
Keyword(s):  
Seismic Analysis ◽  
Evaluation Criteria ◽  
Piping System ◽  
Seismic Loads ◽  
Metallic Component ◽  
Design Practices ◽  
Piping Systems ◽  
Current Design ◽  
New Criteria ◽  
Experimental Background

MECOS is Post-Fukushima OECD/NEA initiative, with the following main objectives: - To quantify the existing margins in seismic analysis of safety class components and assess the existing design practices within a benchmark activity. - To make proposals for new design/evaluation criteria of pressurized piping systems, accounting for their actual failure mode under strong input motions. The first part of MECOS consisted of gathering information on i) current design practices and ii) piping system experimentation carried out around the world that could be suitable for benchmarking. Part 2 is the benchmark itself and Part 3 proposals for new criteria. The purpose of the proposed paper is to present the experimental background and the benchmark exercise.

The OECD-NEA Programme on Metallic Component Margins Under High Seismic Loads (MECOS): Towards New Criteria

2017 ◽  
Author(s):  
Pierre Sollogoub
Keyword(s):  
Failure Modes ◽  
Seismic Analysis ◽  
Evaluation Criteria ◽  
Plastic Instability ◽  
Piping System ◽  
Metallic Component ◽  
Design Practices ◽  
Piping Systems ◽  
Seismic Tests ◽  
New Criteria

MECOS is a Post-Fukushima OECD/NEA initiative, with the following main objectives: • To quantify the existing margins in seismic analysis of safety class components and assess the existing design practices within a benchmark activity. • To make proposals for new design/evaluation criteria of pressurized piping systems, accounting for their actual failure mode under strong input motions. The first part of MECOS consisted of gathering information on i) current design practices and ii) dynamic seismic tests on piping system carried out around the world that could be suitable for benchmarking. Part 2 is a benchmark exercise on piping system tests, and Part 3 are proposals for new criteria. The purpose of the proposed paper is to introduce the work which is undertaken in Part 3 in order to propose design criteria that address the observed fatigue-ratchetting failure modes as well as plastic instability. It includes revisiting the past test results as well as the interpretations that were carried out and conclusions that were drawn at that time, and reanalyzing them in the light of recent developments. Recent experimental programs carried out in Japan and in India will also be addressed.

Main Issues on the Seismic Design of Industrial Piping Systems and Components

2013 ◽  
Author(s):  
Fabrizio Paolacci ◽  
Md. Shahin Reza ◽  
Oreste S. Bursi ◽  
Arnold M. Gresnigt ◽  
Anil Kumar
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Experimental Investigations ◽  
Piping System ◽  
Analysis And Design ◽  
Correct Definition ◽  
Component Design ◽  
Piping Systems ◽  
Current Design ◽  
Bolted Flange

A significant number of damages in piping systems and components during recent seismic events have been reported in literature which calls for a proper seismic design of these structures. Nevertheless, there exists an inadequacy of proper seismic analysis and design rules for a piping system and its components. Current seismic design Codes are found to be over conservative and some components, e.g., bolted flange joints, do not have guidelines for their seismic design. Along this line, this paper discusses about the main issues on the seismic analysis and design of industrial piping systems and components. Initially, seismic analysis and component design of refinery piping systems are described. A review of current design approaches suggested by European (EN13480:3) and American (ASME B31.3) Codes is performed through a Case Study on a piping system. Some limits of available Codes are identified and a number of critical aspects of the problem e.g., dynamic interaction between pipes and rack, correct definition of the response factor and strain versus stress approach, are illustrated. Finally, seismic performance of bolted flange joints based on the results of experimental investigations carried out by the University of Trento, Italy, will be discussed.

Seismic Fragility of Piping Nozzles in Nuclear Power Plants: A Case for Updating the Current State-of-Practice

2021 ◽  
Author(s):  
Abhinav Gupta ◽  
Ankit Dubey ◽  
Sunggook Cho
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Seismic Analysis ◽  
Nuclear Industry ◽  
Life Extension ◽  
Seismic Loads ◽  
Thermal Loads ◽  
Loss Of Coolant Accident ◽  
Piping Systems ◽  
Recent Developments

Abstract Nuclear industry spends enormous time and resources on designing and managing piping nozzles in a plant. Nozzle locations are considered as a potential location for possible failure that can lead to loss of coolant accident. Industry spends enormous time in condition monitoring and margin management at nozzle locations. Margins against seismic loads play a significant role in the overall margin management. Available margins against thermal loads are highly dependent upon seismic margins. In recent years, significant international collaboration has been undertaken to study the seismic margin in piping systems and nozzles through experimental and analytical studies. It has been observed that piping nozzles are highly overdesigned and the margins against seismic loads are quite high. While this brings a perspective of sufficient safety, such excessively high margins compete with available margins against thermal loads particularly during the life extension and subsequent license renewal studies being conducted by many plants around the world. This paper focuses on identifying and illustrating two key reasons that lead to excessively conservative estimates of nozzle fragilities. First, it compares fragilities based on conventional seismic analysis that ignores piping-equipment-structure interaction on nozzle fragility with the corresponding assessment by considering such interactions. Then, it presents a case that the uncertainties considered in various parameters for calculating nozzle fragility are excessively high. The paper identifies a need to study the various uncertainties in order to achieve a more realistic quantification based on recent developments in our understanding of the seismic behavior of piping systems.

Performance-Based Analysis of Coupled Support Structures and Piping Systems Subject to Seismic Loading

2015 ◽  
Author(s):  
Oreste S. Bursi ◽  
Fabrizio Paolacci ◽  
Md Shahin Reza
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Design Method ◽  
Design Guidelines ◽  
Piping System ◽  
Support Structures ◽  
Limit States ◽  
Piping Systems ◽  
Allowable Stress Design

The prevailing lack of proper and uniform seismic design guidelines for piping systems impels designers to follow standards conceived for other structures, such as buildings. The modern performance-based design approach is yet to be widely adopted for piping systems, while the allowable stress design method is still the customary practice. This paper presents a performance-based seismic analysis of petrochemical piping systems coupled with support structures through a case study. We start with a concept of performance-based analysis, followed by establishing a link between limit states and earthquake levels, exemplifying Eurocode and Italian prescriptions. A brief critical review on seismic design criteria of piping, including interactions between piping and support, is offered thereafter. Finally, to illustrate actual applications of the performance-based analysis, non-linear analyses on a realistic petrochemical piping system is performed to assess its seismic performance.

Effects of High Frequency Hydrodynamic Loads on Structural Integrity and Mechanical Operability of Valves

2015 ◽  
Author(s):  
Yigit Isbiliroglu ◽  
Cagri Ozgur ◽  
Evren Ulku ◽  
Nish Vaidya ◽  
Kristofor Paserba
Keyword(s):  
High Frequency ◽  
Structural Integrity ◽  
Energy Content ◽  
Hybrid Approach ◽  
Piping System ◽  
Seismic Loads ◽  
Damage Potential ◽  
Element Analysis ◽  
Piping Systems ◽  
Number Of Cycles

In-line valves are qualified for static as well as dynamic loads from seismic and hydrodynamic (HD) events. Seismic loads are generally characterized by frequency content less than about 33 Hz whereas HD loads may exhibit a broad range of frequencies greater than 33 Hz. HD loads may also result in spectral accelerations significantly in excess of those due to the design basis seismic events. Current regulatory guidelines do not specifically address the evaluation of equipment response to high frequency loading. This paper investigates the response of skid and line mounted valves of piping systems under HD loads by using several independent rigorous finite element analysis solutions for various piping system segments. It presents a hybrid approach for the evaluation of the response of valves to HD and seismic loads. The proposed approach significantly reduces the amount of individual analysis and testing needed to qualify the valves. First, valve responses are evaluated on the basis of displacements since HD loads are generally characterized by high frequencies and small durations. Second, the damage potential of the loads on the valve actuators is represented by the energy imparted to the actuator quantified in terms of Arias intensity. The rationale for using the energy content is based on the fact that damage due to dynamic loading is related not only to the amplitude of the acceleration response but also to the duration and the number of cycles over which this acceleration is imposed.

Recent Developments in the Seismic Analysis of Multiply Supported Piping Systems

2004 ◽  
Author(s):  
Abhinav Gupta
Keyword(s):  
System Analysis ◽  
Seismic Analysis ◽  
Coupled System ◽  
Coupled Systems ◽  
Coupled Analysis ◽  
Piping System ◽  
Modal Damping ◽  
Peak Broadening ◽  
Piping Systems ◽  
Recent Developments

This paper presents results from some of the recent studies on seismic analysis of multiply supported piping systems. The seismic responses for an actual feedwater piping system as evaluated from the conventional uncoupled analysis are compared with those obtained from an analysis of the coupled building-piping system. A discussion is also presented on the significance of non-classical damping in such analyses. It is illustrated that the composite modal damping is just another form of classical damping. Consideration of composite modal damping in a coupled analysis can give inaccurate piping responses when the modes of uncoupled systems are nearly tuned. In such systems, the effect of nonclassical damping is quite significant. Since the floor spectra are neither generated nor required in a coupled systems analysis, methods like peak broadening or peak shifting cannot be used directly to account for the effect of uncertainties. Formulations are presented to evaluate the design response from a coupled system analysis by considering the effect of uncertainties in modal properties of uncoupled systems.

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.

Introduction of a Research Activity on the Seismic Safety Evaluation of Nuclear Piping Systems Taking the Effect of Elastic-Plastic Behavior Into Account

2015 ◽  
Author(s):  
Izumi Nakamura ◽  
Masaki Shiratori ◽  
Akihito Otani ◽  
Masaki Morishita ◽  
Tadahiro Shibutani ◽  
...  
Keyword(s):  
Seismic Load ◽  
Failure Behavior ◽  
Plastic Behavior ◽  
Piping System ◽  
Seismic Loads ◽  
Research Activity ◽  
Standard Analysis ◽  
Seismic Safety ◽  
Elastic Plastic ◽  
Piping Systems

According to investigations of several nuclear power plants (NPPs) hit by actual seismic events and a number of experimental researches on the failure behavior of piping systems under seismic loads, it is recognized that piping systems used in NPPs include a large seismic safety margin until boundary failure and the current code design allowable stresses are very conservative. Since the stress assessment based on the elastic analysis does not reflect actual response of piping systems including plastic region, rational procedures to estimate the elastic-plastic behavior of piping systems under a large seismic load are expected to be developed for piping seismic design applications. With the aim of establishing a procedure that takes into account the elastic-plastic behavior effect in the seismic safety estimation of nuclear piping systems, a research activity has been planned. Through the activity, the authors intend to establish two kinds of guidelines; 1) a guideline of a standard analysis procedure to evaluate elastic-plastic behavior of piping systems under extreme seismic loads with rational and conservative margins, and 2) a guideline that provide criteria for the seismic safety assessment of piping systems by the standard analysis to evaluate elastic-plastic behavior established by the above guideline. As the first step of making out the analysis guideline, benchmark analyses are conducted for a pipe element test and a piping system test. In this paper, the outline of the research activity and the preliminary results of benchmark analyses for a pipe element test are described.

Linearization Techniques for Seismic Analysis of Piping System on Friction Support

1999 ◽  
Vol 121 (1) ◽  
pp. 103-108 ◽  
Author(s):  
G. R. Reddy ◽  
K. Suzuki ◽  
T. Watanabe ◽  
S. C. Mahajan
Keyword(s):  
Energy Method ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Equivalent Linearization ◽  
Piping System ◽  
Response Spectrum Method ◽  
Equivalent Damping ◽  
Spectrum Method ◽  
Piping Systems ◽  
Linearization Techniques

Generally, industrial piping systems are supported on hangers, snubbers, friction supports, etc. Friction supports are used for free thermal expansion of the piping systems. They also have the property to absorb energy from earthquake excitation. In this paper, equivalent linearization techniques such as the Caughey method for bilinear system and the energy method are used to calculate equivalent damping of typical industrial piping system on friction support. These methods are compared in terms of the equivalent damping. An iterative response spectrum method is tried for evaluating response of the piping system using equivalent damping obtained by linearization techniques. Maximum response displacement obtained at friction support is compared with the experimental values. At the end it is concluded that the Caughey method and the energy method evaluate similar damping for the piping on friction support and also concluded that the iterative response spectrum method is easy and reasonable for use in design.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

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