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.

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.

Seismic Evaluation Method of Piping Systems by Inelastic Response Spectrum Analysis: Part 1 — Response Analysis

2019 ◽  
Author(s):  
Ichiro Tamura ◽  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Ryuya Shimazu ◽  
Hiroaki Tamashiro ◽  
...  
Keyword(s):  
Spectrum Analysis ◽  
Evaluation Method ◽  
Response Spectrum ◽  
Vibration Test ◽  
Piping System ◽  
Analysis Method ◽  
Seismic Evaluation ◽  
Response Spectrum Analysis ◽  
Inelastic Response ◽  
Piping Systems

Abstract An inelastic response-spectrum-analysis method for multi-degree-of-freedom systems was proposed. The method has lower analysis loads and good outlook given by the inelastic response spectrum like the elastic response-spectrum-analysis method, and is not an equivalent-linearization method. We propose a seismic evaluation method of piping systems to conduct seismic design using the inelastic response-spectrum-analysis. In this paper, the inelastic analysis method of piping systems for the seismic evaluation method is proposed and applied to a benchmark analysis problem of a piping system vibration test. The analysis result is compared with the vibration test result of the piping system. They are consistent and applicability of the analysis to the piping system was confirmed.

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: 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.

Seismic Qualification of Piping Systems by Detailed Inelastic Response Analysis: Part 3 — Variation in Elastic-Plastic Analysis Results on Carbon Steel Pipes From the Benchmark Analyses and the Parametric Analysis

2017 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Morishita ◽  
Masaki Shiratori ◽  
Tomoyoshi Watakabe ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Evaluation Procedure ◽  
Response Analysis ◽  
Seismic Load ◽  
Inelastic Response ◽  
Elastic Plastic ◽  
Analytical Results ◽  
Plastic Analysis ◽  
Piping Systems ◽  
Parametric Analyses

It is recognized that piping systems used in nuclear power plants have a significant amount of the safety margin, up to the point of boundary failure, even when the input seismic load exceeds the allowable design level. The reason is attributed to the large strength capacity of the piping systems in the plastic region. In order to establish an evaluation procedure, in which the inelastic behavior of piping systems is considered in a rational way, a task group activity under the Japan Society of Mechanical Engineers (JSME) has been conducted. As a deliverable of this activity, a Code Case in the framework of the JSME Nuclear Codes and Standards is now being developed. The Code Case provides the strain-based criteria, an evaluation procedure using the response-spectrum based inelastic analysis, and detailed inelastic response analysis based on a finite element model. For developing the Code Case, inelastic benchmark and parametric analyses of the tests of a pipe element and piping system made of carbon steel were conducted to investigate the variation of the elastic-plastic analyses results. Based on these analytical results, it is assumed that setting the yield stress has a significant influence on the inelastic analytical results, while the work hardening modulus in the bi-linear approximation of the stress-strain curve has little influence. From the results of the parametric analyses, it is confirmed that the variation in the analytical results among the analysts would be reduced by having a unifying analysis procedure. In this paper, the results of the parametric analyses and the variation in the elastic-plastic analysis are discussed.

On Categorization of Seismic Load As Primary or Secondary for Piping Systems With Hardening Capacity

2018 ◽  
Author(s):  
Pierre B. Labbé
Keyword(s):  
Natural Frequency ◽  
Response Spectrum ◽  
A Priori ◽  
Effective Stiffness ◽  
Linear Oscillator ◽  
Seismic Load ◽  
Wide Range ◽  
Non Linear ◽  
Piping Systems ◽  
Non Linear Oscillator

The concept of primary/secondary categorization is first reviewed and generalized for its application to a non-linear oscillator subjected to a seismic load. Categorizing the seismic load requires calculating the input level associated with the oscillator ultimate capacity and comparing it to the level associated with the plastic yield. To resolve this problem, it is assumed that the non-linear oscillator behaves like a linear equivalent oscillator, with an effective stiffness (or frequency) and an effective damping. However, as it is not a priori possible to predict the equivalent stiffness and damping, a wide range of possibilities is systematically considered. The input motion is represented by its conventional response spectrum. It turns out that key parameters for categorization are i) the “effective stiffness factor” (varying from 0 for perfect damage behaviour to 1 for elastic-perfectly plastic) and the slope of the response spectrum in the vicinity of the natural frequency of the oscillator. Effective damping and spectrum sensitivity to damping play a second order role. A formula is presented that enables the calculation of the primary part of a seismically induced stress as a function of both the oscillator and input spectrum features. The formula is also presented in the form of a diagram. This paper follows-up on a similar paper presented by the author at the PVP 2017 Conference [1]. The new development introduced here is that the oscillator exhibits hardening capacity, while no hardening was assumed in [1]. It appears that the conclusions are slightly modified but the trend is very similar to the non-hardening case. Regarding piping systems, it appears that even when experiencing large plastic strains under beyond design input motions, their observed effective frequency is very close to their natural frequency, decreasing only by a few percents (experimental data from USA, Japan and India are processed). These observations lead to the conclusion that the seismic load, or the seismically induced inertial seismic strains, should basically be regarded as secondary.

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.

A Load Combination Method for Aseismic Design of Multiple Supported Piping Systems

1989 ◽  
Vol 111 (1) ◽  
pp. 10-16 ◽  
Author(s):  
K. Suzuki ◽  
A. Sone
Keyword(s):  
Structural Model ◽  
Response Spectrum ◽  
Reduction Factor ◽  
Combination Method ◽  
Piping System ◽  
Response Reduction Factor ◽  
Load Combination ◽  
Combination Scheme ◽  
Piping Systems ◽  
Reduction Effect

A new load combination scheme for seismic response calculation of piping systems subjected to multiple support excitations is presented. This scheme has an advantage, such that the cross-correlation among support excitations are properly taken into account by use of a stationary random vibration approach. The authors also present the idea of generating a “multi-excitation floor response spectrum.” First, using a simple analytical SDOF piping system to two support excitations and a simple Z-shaped piping model for shaking test, the combination law is supplied to various correlation cases of two support excitations and the maximum responses of piping in a fundamental mode is calculated. Second, nonlinear characteristics such as gap and friction appearing between piping itself and supports are specifically investigated. The response effect due to these nonlinearities is evaluated by the results through the shaking test with a piping-support structural model, and the amount of response reduction effect is represented by “a response reduction factor β.”

Creep Relaxation Behavior of High-Energy Piping

2000 ◽  
Vol 122 (4) ◽  
pp. 488-493 ◽  
Author(s):  
Raymond K. Yee ◽  
Marvin J. Cohn
Keyword(s):  
Stress Relaxation ◽  
Thermal Loading ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Creep Damage ◽  
High Energy ◽  
External Loading ◽  
Piping System ◽  
Dead Weight ◽  
Piping Systems

The analysis of the elastic stresses in high-energy piping systems is a routine calculation in the power and petrochemical industries. The American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code was developed for safe design and construction of pressure piping. Postconstruction issues, such as stress relaxation effects and selection of maximum expected creep damage locations, are not addressed in the Code. It has been expensive and time consuming to evaluate creep relaxation stresses in high energy piping systems, such as main steam and hot reheat piping. After prolonged operation of high-energy piping systems at elevated temperatures, it is very difficult to evaluate the redistribution of stresses due to dead weight, pressure, external loading, and thermal loading. The evaluation of stress relaxation and redistribution is especially important when nonideal conditions, such as bottomed-out or topped-out hangers, exist in piping systems. This paper uses three-dimensional four-node quadrilateral shell elements in the ABAQUS finite element code to evaluate the time for relaxation and the nominal relaxation stress values for a portion of a typical high-energy piping system subject to an ideally loaded hanger or to an overloaded hanger. The stress relaxation results are evaluated to suggest an approximation using elastic stress analysis results. [S0094-9930(00)01304-4]

Simplified Second Stage Creep/Relaxation Analysis of Moderately Complex Spatially Three-Dimensional Piping Systems

1974 ◽  
Vol 96 (3) ◽  
pp. 184-192 ◽  
Author(s):  
G. H. Workman ◽  
E. C. Rodabaugh
Keyword(s):  
Three Dimensional ◽  
Theoretical Development ◽  
Small Displacement ◽  
Piping System ◽  
Stress Strain ◽  
Curved Pipe ◽  
Thermal Change ◽  
Second Stage ◽  
Piping Systems ◽  
Applied Forces

An analysis technique for predicting the second stage creep/relaxation response of moderately complex spatially three-dimensional piping systems is presented herein. The theoretical development of this technique is based on two major assumptions. The first assumption is that at any time the behavior of the piping system can be associated with two components. One is an elastic component which is recoverable, and the other is a creep/relaxation component, which is not recoverable. The second major assumption, the simplifying assumption, is that the creep/relaxation strains due to axial, bending, and torsional loading can be decoupled and strains due to internal pressure can be neglected. Utilizing small displacement linear strain assumptions, the elastic stress-strain and creep/relaxation stress-strain rate laws can be integrated over the pipe’s cross section to yield generalized force-deformation relationships. The method of initial strains associated with the matrix displacement method of structural analysis is now applied to generate the solution of the creep/relaxation problem. This formulation utilizes two distinct types of piping elements. The first is a straight uniform pipe element and the second is a circularly curved pipe element, which incorporates both elastic and creep/relaxation flexibility factors. The end result of this formulation is a digital computer program capable of analyzing spatially three-dimensional piping systems under creep/relaxation conditions that can be represented by a series of straight or circularly curved pipe elements subjected to applied forces, displacements, and/or thermal change. An example analysis is included.

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