Comparative Evaluation of Mode Combination Methods in Seismic Analysis Using Response Spectrum Method for Tank Structure Using FEA - Seismic FEA

2011 ◽  
Vol 110-116 ◽  
pp. 5240-5248
Author(s):  
Sujay Shelke ◽  
H.V. Vankudre ◽  
Vinay Patil
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Initial Step ◽  
Relative Displacement ◽  
Geometrical Parameters ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Combination Methods ◽  
Eigen Values ◽  
Modes Of Vibration

Typical seismic analysis using response spectrum method involves several steps from the initial step of extracting the modes. At the initial stage Eigen values are extracted corresponding to the modes of vibration. These give us Eigen vectors which are a series of relative displacement shapes; however these do not correspond to real displacements or stresses. Participation factors asses these Eigen vectors and grades them according to contribution they will have to the overall solution. Based on the spectral seismic acceleration, participation factor is used to calculate the mode coefficient, which is more of a scaling factor to give physical meaning to the values. Once the modes are extracted, the key issue is of combining these modes to obtain the seismic response. The modes cannot be added algebraically in reality as all the modes do not occur at the same time. Hence we employ methods which can add the modes in a more realistic manner. The objective of this paper is to do a comparative study of various mode combination methods with a focus on tank structures and study the effect of various geometrical parameters on the combination methods

Rational and Economical Multicomponent Seismic Design of Piping Systems

1978 ◽  
Vol 100 (4) ◽  
pp. 425-427
Author(s):  
A. K. Gupta
Keyword(s):  
Shear Stress ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Maximum Shear Stress ◽  
Strength Criterion ◽  
New Method ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Piping Systems ◽  
Modes Of Vibration

The seismic analysis of complex piping systems is often carried out by the response spectrum method. The maximum probable responses are calculated as the square root of the sum of the squares (SRSS) of the responses obtained in various modes of vibration for the three components of earthquake. A coupling matrix is introduced in case of modes with closely spaced frequencies. The ASME strength criterion for the pipes is based on maximum shear stress which can be calculated from the two orthogonal bending moments and the torsional moment acting on the cross section. Strictly speaking, one should know the combination of these three moments acting simultaneously which would give the maximum shear stress at the section being designed. However, the response spectrum method gives the maximum probable values which in general do not occur simultaneously. Often the pipe is conservatively designed as if these probable maximum values were occurring simultaneously. It can be shown that this procedure may overestimate the maximum shear stress by as much as 73 percent. To overcome this problem a new method is applied by which simultaneous variation in the three moments can be predicted to cause the extreme probable effect. The new method is “exact” within the framework of existing procedures and assumptions.

Research on the Seismic Analysis and Optimization of High Flux Reactor Nuclear Power Piping System Based on Multi-Point Response Spectrum Method

2020 ◽  
Author(s):  
Xuan Huang ◽  
Pingchuan Shen ◽  
Shuai Liu ◽  
Jian Liu ◽  
Xiaozhou Jiang ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
High Flux ◽  
Analysis Method ◽  
Response Spectrum Method ◽  
High Flux Reactor ◽  
Reactor Coolant ◽  
Spectrum Method ◽  
Flux Reactor ◽  
Coolant System

Abstract High flux reactor is an important engineering test reactor, which can be used in irradiation research of materials, chemistry, isotopes, medicine and other fields. In the high flux reactor coolant system, there are a large number of nuclear pipes and the layout is complex. The optimization of seismic analysis method for reactor coolant system is an important part in the design process to ensure the nuclear pipes meet the design specifications. The traditional single point response spectrum method needs to envelope the response spectrum of different floors as the analysis input. This method is difficult to give the reasonable seismic load to the numerous nuclear pipes and it will increase the design cost and the difficulty of safety analysis about nuclear pipe. In this paper, an optimized seismic analysis method of reactor coolant system is proposed. By using the multi-point response spectrum method, the optimization of different excitation loading modes for different constrained support points is realized. The analysis results show that the multi-point response spectrum method can solve the problem that different support points are located at different elevation floors in the reactor coolant system, which makes the calculation results more accurate and reasonable. Compared with the traditional method, it can make the design more efficient and practical.

scholarly journals Seismic Behaviour of Offshore Steel Jacket Platform Braced in Horizontal and Vertical Planes

2019 ◽  
Vol 8 (12) ◽  
pp. 1947-1953
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Vertical Plane ◽  
Static Method ◽  
Base Shear ◽  
Response Spectrum Method ◽  
Seismic Behaviour ◽  
Jacket Platform ◽  
Spectrum Method ◽  
Time Period

The offshore jacket platforms are primarily installed in the large oceans mainly for drilling the crude oil, carbohydrates and production of electricity. The current studies emphasize on the structural performance of offshore deck jacket platform with different bracing systems. Earthquake analysis has been performed to calculate the seismic responses, with the help of bracings to control the seismic induced vibrations of the jacket platforms. For this study, a jacket platform made up of steel members has been modeled and then analyzed under earthquake and wave loadings. This paper mainly deals to compute and compare the seismic behavior of offshore steel deck platform using SAP 2000 v20 software with bracing in the horizontal plane and bracing in both horizontal and vertical planes. The total number of 8 models has been analyzed in the SAP2000 software with bracing i.e. X, V, Inverted V and K in the vertical plane and bracing i.e. X, V, Inverted V and K in both horizontal and vertical plane. A relative study has been carried out in Time period, deck displacement and base shear. Seismic analysis using linear static, i.e. Equivalent static method (ESA) and linear dynamic, i.e. Response spectrum method (RSA) has been performed. Further deck displacement, time period and base shear are determined by Equivalent static method and Response spectrum method for various types of bracing models in both horizontal and vertical planes. Among the all various types of bracing models, Inverted V bracing in the vertical plane is found to be the optimum model among all other models.

Insights Gleaned From NRC-BNL Benchmark Evaluation of Seismic Analysis Methods for Non-Classically Damped Coupled Systems

2004 ◽  
Vol 126 (1) ◽  
pp. 75-84 ◽  
Author(s):  
J. Xu ◽  
G. DeGrassi ◽  
N. Chokshi
Keyword(s):  
Normal Mode ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Time History ◽  
Computer Programs ◽  
Coupled Systems ◽  
Response Spectrum Method ◽  
Complex Mode ◽  
Spectrum Method ◽  
Mode Response

Under the auspices of the US Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) developed a comprehensive program to evaluate state-of-the-art methods and computer programs for seismic analysis of typical coupled nuclear power plant (NPP) systems with non-classical damping. In this program, four benchmark models of coupled building-piping/equipment systems with different damping characteristics were developed and analyzed by BNL for a suite of earthquakes. The BNL analysis was carried out by the Wilson-θ time domain integration method with the system-damping matrix computed using a synthesis formulation as presented in a companion paper [Xu, J., 2003, Nuclear Eng. Des. These benchmark problems were subsequently distributed to and analyzed by program participants applying their uniquely developed methods and computer programs. This paper presents the insights gleaned from the participants’ analyses, and the comparison of their results to the BNL time history solutions. The participant’s results established using complex modal time history methods showed close agreement with the BNL solutions, while the analyses produced with either complex-mode response spectrum methods or classical normal-mode response spectrum method, in general, produced relatively conservative results, when averaged over a suite of earthquakes. However, when coupling due to damping is significant, complex-mode response spectrum methods performed better than the classical normal-mode response spectrum method. Furthermore, as part of the program objectives, a parametric assessment is performed aiming at evaluating the applicability and sensitivity of various analysis methods to problems with different dynamic characteristics unique to coupled NPP systems. It is believed that the findings and insights learned from this program are useful in developing new acceptance criteria and providing guidance for future regulatory activities involving licensing applications of these alternate methods to coupled systems.

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.

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