scholarly journals Approach for Selection of Rayleigh Damping Parameters Used for Time History Analysis

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
R. E. Spears ◽  
S. R. Jensen
Keyword(s):  
Seismic Analysis ◽  
Time History ◽  
System Response ◽  
Piping System ◽  
Nuclear Facilities ◽  
Rayleigh Damping ◽  
Modal Damping ◽  
American Society ◽  
Selection Of ◽  
Civil Engineers

Nonlinearities, whether geometric or material, need to be addressed in seismic analysis. One good analysis method that can address these nonlinearities is direct time integration with Rayleigh damping. Modal damping is the damping typically specified in seismic analysis Codes and Standards (ASCE 4-98, 1998, “Seismic Analysis of Safety-Related Nuclear Structures and Commentary,” American Society of Civil Engineers, Reston, Virginia and ASCE/SEI 43-05, 2005, “Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities,” American Society of Civil Engineers, Reston, Virginia.). Modal damping is constant for all frequencies where Rayleigh damping varies with frequency. An approach is proposed here for selection of Rayleigh damping coefficients to be used in seismic analyses that is consistent with given modal damping. The approach uses the difference between the modal damping response and the Rayleigh damping response along with effective mass properties of the model being evaluated to match overall system response levels. This paper provides a simple example problem to demonstrate the approach. It also provides results for a finite element model representing an existing piping system. Displacement, acceleration, and stress results are compared from model runs using modal damping and model runs using Rayleigh damping with coefficients selected using the proposed method.

scholarly journals Approach for Selection of Rayleigh Damping Parameters Used for Time History Analysis

2009 ◽  
Author(s):  
R. E. Spears ◽  
S. R. Jensen
Keyword(s):  
Seismic Analysis ◽  
Time Integration ◽  
Time History ◽  
Element Model ◽  
System Response ◽  
Piping System ◽  
Rayleigh Damping ◽  
Modal Damping ◽  
The Difference ◽  
Selection Of

Nonlinearities, whether geometric or material, need to be addressed in seismic analysis. One good analysis method that can address these nonlinearities is direct time integration with Rayleigh damping. Modal damping is the damping typically specified in seismic analysis Codes and Standards [1, 2]. Modal damping is constant for all frequencies where Rayleigh damping varies with frequency. An approach is proposed here for selection of Rayleigh damping coefficients to be used in seismic analyses that are consistent with given Modal damping. The approach uses the difference between the modal damping response and the Rayleigh damping response along with effective mass properties of the model being evaluated to match overall system response levels. This paper provides a simple example problem to demonstrate the approach. It also provides results for a finite element model representing an existing piping system. Displacement, acceleration, and stress results are compared from model runs using modal damping and model runs using Rayleigh damping with coefficients selected using the proposed method.

A Parametric Study of Independent Support Motion Method for the Steam Supply Piping Connected to the HP Turbine of APR 1400

2013 ◽  
Author(s):  
Dae Soo Kim ◽  
Joon Ho Lee ◽  
In Yeung Kim
Keyword(s):  
High Pressure ◽  
Power Plant ◽  
Support Groups ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Nuclear Industry ◽  
Combination Method ◽  
Piping System ◽  
Support Motion

The steam supply piping connected to the high pressure (HP) turbine of APR1400 (Korea’s advanced power plant 1400 MW-class) is a typical example of multi-supported piping system, and it is routed from the Containment building to the Turbine building via the Main Steam Isolation Valve House in the Auxiliary building. In the seismic analysis of this piping system, using the Enveloped Response Spectrum (ERS) method, a commonly used methodology for seismic analysis of nuclear power plant piping in industry circles, generates overly conservative analysis results. Therefore, Time History Method (THM) which applies excitation characteristic of each support attached to individual building was used to eliminate unnecessary conservatism. However, it was noticed that the Time History Method requires considerable amount of labor and time in generating combined time history equivalent to the spectrum applied for each support although it is regarded as the most exact and realistic method for seismic analysis. The nuclear industry has been making lots of efforts in finding out the mathematic logicality and practical applicability to resolve this issue. This paper deals with parametric research on combination effects of responses between support groups, damping effects, and modal combination method with close modes in applying the Independent Support Motion (ISM) method to the analysis model of the steam supply piping connected to the high pressure turbine of APR1400. Quantitative assessment and comparison with the analysis results of the ERS method and THM were also carried out. As a result, it is shown that the analysis results of the ISM method together with the SRSS combination between support groups, 4% damping with ±15% spectrum peak broadening and grouping of modal combination are remarkably similar to those of THM.

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.

Sensitivity of the Effective Seismic Support Damping in a Class I Piping System to Analysis Parameters

2009 ◽  
Author(s):  
Nima Zobeiry
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Class I ◽  
Piping System ◽  
Frequency Content ◽  
Response Spectrum Analysis ◽  
History Analysis ◽  
The Coefficient Of Friction ◽  
Seismic Damping

It is understood that the level of seismic damping in a piping system is strongly influenced by the supports. Put differently, the supports contribute to an effective damping that can be considered in the seismic analysis of the piping system. This paper investigates the issue for the feeder pipes of a CANDU™ reactor. Feeders are numerous class I pipes in parallel, which are separated by frictional spacer elements. The results of a time history analysis, taking into account different damping mechanisms, are compared to those from a response spectrum analysis to deduce the effective damping in the system. The sensitivity of the effective damping to different parameters, such as the coefficient of friction and the input frequency content, is investigated.

Seismic Design Challenges of High Pressure Riser Systems on Gravity Based Structures

2019 ◽  
Author(s):  
Mahesh Sonawane ◽  
Rohit Vaidya ◽  
Ronak Kadakia ◽  
Hunter Haeberle ◽  
Phil Ward
Keyword(s):  
High Pressure ◽  
Case Studies ◽  
Seismic Analysis ◽  
Interaction Model ◽  
Time History ◽  
Seismic Loading ◽  
System Response ◽  
Seismic Load ◽  
Adjacent Structures ◽  
Ground Motion Records

Abstract This paper presents two case studies of the seismic analysis of high pressure riser and conductor systems used on shallow water fixed platforms (approximately 120m water depth) offshore Newfoundland and Labrador, Canada. The case studies presented consider the Hebron and White Rose extension Husky gravity-based concrete platforms. A methodology is presented to assess the dynamic and resonant response of each conductor and riser system to seismic loading using a fully integrated conductor and platform interaction model. Seismic loading is an application of an earthquake-generated agitation to a structure. This occurs at contact surfaces either with the ground, or with adjacent structures, or with gravity waves. Nonlinear time history analyses of the riser system subjected to various ground motion records are performed to simulate the seismic load. Design considerations that drive the HP riser design are discussed. The paper addresses the intricacies of the gravity base concrete platform-riser system interaction, initial configuration and dynamic seismic response. The riser and conductor system response is used to determine HP riser connector and centralization requirements. The learnings taken from the detailed modeling method are presented along with the advantages of this methodology.

Floor Response Spectrum Method of Multiply Supported Piping System Assisted by Time History Analysis

2020 ◽  
Author(s):  
Yoshihiro Takayama ◽  
Ayaka Yoshida ◽  
Iriki Nobuyoshi ◽  
Eiichi Maeda
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Correlation Coefficients ◽  
Time History Analysis ◽  
Piping System ◽  
Response Spectrum Method ◽  
Sum Rule ◽  
Spectrum Method ◽  
History Analysis

Abstract The independent support motion response spectrum method (ISM) is currently used for seismic analysis to calculate the response of multiply supported piping with independent inputs of support excitations. This approach may derive considerable overestimation in the combination of group responses under the absolute sum rule of NUREG-1061 [1]. Then authors have developed an advanced method of the ISM approach named SATH (Spectrum Method Assisted by Time History Analysis). In the SATH method, both of floor response spectra and time histories of floor acceleration are used as independent inputs of support excitations. The group responses are summed with correlation coefficients which are calculated by considering each time history of modal response by independent inputs of support excitations. In this paper, the necessity of taking the effects of correlation coefficients for the group responses into account in the ISM approach is examined. The SATH method has advantage to derive a more realistic sum rule of the group responses and applicability for the actual design.

Coupled Modelling of a “Flow-Piping” System in Dynamic Analysis

2006 ◽  
Author(s):  
Peter S. Vasilyev
Keyword(s):  
Finite Element ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Mode Shapes ◽  
Coupled Analysis ◽  
Feed Water ◽  
Piping System ◽  
Coupled Modelling ◽  
Basic Fluid

The paper considers the problem of simultaneous modeling of structure and flow in a piping system. It takes a middle road between full coupled analysis on the one hand, and the simplified case of treating the liquid as a rigid mass. The suggested method allows the use of standard beam and rod elements for the analysis. Two approaches to the problem of dynamic interaction between pipe and medium are compared in the given paper: 1) The first one treats medium as mass rigidly connected to the pipe finite-element model’s nodes. 2) In the second one medium is modeled by the finite-element system of rod-elements. In this case the basic fluid-structure interaction (FSI) effects are taken into account. The main techniques for FE modeling of some pipeline elements are presented in the paper. The second approach can be implemented by the use of general purpose FE programs. A model of a feed water pipeline of VVER-440 type NPP has been developed to study how the FSI affects on pipeline response. The results of the analysis which allow estimation of inaccuracy arising from medium dynamics neglecting are as follows: • calculation of eigen frequency and mode shapes; • seismic analysis using the response-spectrum method; • accidental blast impact assessment with the use of time history analysis; • operating vibration assessment on the basis of harmonic analysis. It has become apparent that the way of medium modeling has an essential influence on the dynamic behavior of pipelines.

scholarly journals Taking into Account Material Damping in Seismic Analysis of Structures

2020 ◽  
Vol 14 (1) ◽  
pp. 55-59
Author(s):  
Maria S. Barabash ◽  
Bogdan Y. Pysarevskyi ◽  
Yaroslav Bashynskyi
Keyword(s):  
Seismic Analysis ◽  
Time History ◽  
Physical And Mechanical Properties ◽  
Time History Analysis ◽  
Material Damping ◽  
Damping Coefficients ◽  
Modal Damping ◽  
History Analysis ◽  
Earthquake Load ◽  
Displacement Speed

The purpose of this paper is to justify that it is necessary to take into account physical and mechanical properties of soil and different materials of erected structures for damping vibrations in dynamic loads, and to suggest tools for modelling the damping effect (natural or engineering induced) between foundation and soil. A technique is suggested for modelling the behavior of structure in time history analysis taking into account material damping. When solving this problem, the following results were obtained: the physical meaning of material damping was described; Rayleigh damping coefficients were computed through modal damping coefficients. Numerical analysis was carried out for the structure together with soil in earthquake load. Time history analysis was carried out for the problem. Peak values of displacement, speed and acceleration at the roof levels were compared. Analysis results were compared (with and without taking into account material damping). Significant influence of damping on the stress-strain state of the structure has been confirmed.

Design Applicability of the Advanced Spectrum Method Assisted by Time History Analysis for Multiply Supported Piping System

2020 ◽  
Author(s):  
Ayaka Yoshida ◽  
Yoshihiro Takayama ◽  
Hiromichi Shudo
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Response Spectra ◽  
Time History Analysis ◽  
Piping System ◽  
Acceleration Time ◽  
Spectrum Method ◽  
History Analysis ◽  
Acceleration Time Histories

Abstract The independent support motion response spectrum method (ISM) is currently used for seismic analysis to calculate the response of multiply supported piping system with independent inputs of support excitations. This approach may derive considerable overestimation in the combination of group responses under the absolute sum rule of NUREG-1061. To reduce the excessive overestimation, an advanced method named “Spectrum Method Assisted by Time History Analysis (SATH)” has been proposed. In the SATH method, modal responses by multiple excitations are combined with correlation coefficients which are calculated from the covariances and the standard deviations of time history responses of the oscillators having each of modal frequencies of piping system by each of the floor acceleration time history excitations. In this paper, the applicability of the SATH method to actual design which uses broadened Floor Response Spectra (FRS) was examined. Conservativeness of the SATH method is also discussed with presenting that responses derived from the SATH method tend to exceed responses by the time history analysis even when many different time intervals of acceleration time histories are used within the range of the FRS broadening.

Time History Input Development for the Seismic Analysis of Piping Systems

1980 ◽  
Vol 102 (2) ◽  
pp. 212-218 ◽  
Author(s):  
C.-W. Lin
Keyword(s):  
Degrees Of Freedom ◽  
Seismic Analysis ◽  
Time History ◽  
Response Spectra ◽  
Nonlinear Time History Analysis ◽  
System Response ◽  
Ground Response ◽  
Piping Systems ◽  
Statistical Relationships ◽  
Nonlinear Time History

In a nonlinear time history analysis of piping systems, the system response is generally highly coupled for all dynamic degrees-of-freedom. Therefore, the seismic time history input components, which are usually synthesized from the Regulatory Guide 1.60 spectra, play an important role in the piping seismic analysis. The design ground response spectra recommended in Regulatory Guide 1.60 are identical for both horizontal directions. No specific requirements are given to define their statistical relationships. As a result, the two horizontal components could either be identical or with erroneous relationships which could adversely affect the analysis. In this paper, the results of a study conducted to establish statistical relationships on 22 earthquakes are reported. These earthquakes are those used in establishing the design ground response spectra specified in Regulatory Guide 1.60. The statistical properties studied include the autocorrelation functions, crosscorrelation functions, coherence functions, and acceleration motion distribution. A set of criteria is recommended for the generation of the synthesized time histories so that analysis of the piping systems can be realistically and correctly conducted.

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