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.

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.

Response Characteristics of Piping System Supported by Visco-Elastic and Elasto-Plastic Dampers

1990 ◽  
Vol 112 (1) ◽  
pp. 34-38 ◽  
Author(s):  
T. Chiba ◽  
H. Kobayashi
Keyword(s):  
Energy Dissipation ◽  
Seismic Design ◽  
Damping Ratio ◽  
The Other ◽  
Piping System ◽  
Response Level ◽  
Response Characteristics ◽  
Damping Effect ◽  
Component Test ◽  
Piping Systems

Improving the reliability of the piping systems can be achieved by eliminating the mechanical snubber and by reducing the response of the piping. In the seismic design of piping system, damping is one of the important parameters to reduce the seismic response. It is reported that the energy dissipation at piping supports contributes to increasing the damping ratio of piping system. Visco-elastic damper (VED) and elasto-plastic damper (EPD) were developed as more reliable, high-damping piping supports. The dynamic characteristics of these dampers were studied by the component test and the full-scale piping model test. Damping effect of VED is independent of the piping response and VED can be modeled as a complex spring in the dynamic analysis. On the other hand, damping ratio of piping system supported by EPD increases with the piping response level. So, these dampers are helpful to increase the damping ratio and to reduce the dynamic response of piping system.

A New Approach of Piping Dynamic Response Considering Plastic Effect

2006 ◽  
Author(s):  
Yanping Yao ◽  
Ming-Wan Lu ◽  
Xiong Zhang
Keyword(s):  
Dynamic Response ◽  
Bending Moment ◽  
Fem Analysis ◽  
Computational Effort ◽  
Response Analysis ◽  
Plastic Behavior ◽  
Piping System ◽  
Element Analysis ◽  
Equivalent Damping ◽  
Plastic Dissipation

Dynamic response of piping system is significantly affected by plastic deformation. Based on the behavior classification of the pipe subjected to a steady axial force and a cyclic bending moment, the absorbed energy per semi-cycle due to plasticity is calculated for different elasto-plastic behavior. A new efficient piping dynamic response analysis method, plastic dissipation equivalent damping method, is proposed to consider the plastic effect on the basis of equivalence principle of energy dissipation. The proposed scheme is implemented in the finite element analysis code FEAP by introducing the equivalent damping which causes the same energy loss per semi-cycle. Numerical examples indicate that the results obtained by the present method show good agreements with those of elasto-plastic FEM analysis, and that this method can reduce the required computational effort significantly.

Application of JSME Seismic Code Case by Elastic-Plastic Response Analysis to Practical Piping System

2018 ◽  
Author(s):  
Akihito Otani ◽  
Satoru Kai ◽  
Naoaki Kaneko ◽  
Tomoyoshi Watakabe ◽  
Masanori Ando ◽  
...  
Keyword(s):  
Seismic Design ◽  
Evaluation Methodology ◽  
Design Rule ◽  
Design Evaluation ◽  
Response Analysis ◽  
Piping System ◽  
Plastic Response ◽  
Seismic Code ◽  
Elastic Plastic ◽  
Piping Systems

A Code Case in the framework of JSME Nuclear Codes and Standards is being developed to incorporate a seismic design evaluation methodology for piping by means of advanced elastic-plastic response analysis methods and strain-based fatigue criteria. The Code Case as an alternative seismic design rule over the current rule will provide a more rational seismic design evaluation than the current criteria. This paper demonstrates an application result of the JSME Seismic Code Case to an actual complex piping system. The secondary coolant piping system of Japanese Fast Breeder Reactor, Monju, was selected as a representative of the complex piping systems. The elastic-plastic time history analysis for the piping system was performed and the piping system has been evaluated according to the JSME Seismic Code Case. The evaluation by the Code Case provides a reasonable result in terms of the piping fatigue evaluation that governs seismic integrity of piping systems. Moreover, it is found that the supporting forces and the response accelerations of the piping system obtained by the elastic-plastic response analysis also become more rational results than those with the current elastic response analysis. The contradiction of two requirements in piping design, flexibility for thermal expansion and rigidity for seismic response, can be effectively relaxed by use of the Code Case being developed.

Seismic Response Reduction in Piping Systems Using Plastic Deformation of Pipe Support Structures

2012 ◽  
Author(s):  
Tsuneo Takahashi ◽  
Akira Maekawa
Keyword(s):  
Plastic Deformation ◽  
Seismic Response ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Initial Stiffness ◽  
Support Structure ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Piping Systems

This study describes inelastic seismic design of piping systems considering the effect of plastic deformation of a pipe support structure. The damping coefficient of a piping system is focused on, and the relation between seismic response of the piping system and elastic-plastic behavior of the support structure was studied using nonlinear time history analysis and complex eigenvalue analysis. The analysis results showed that the maximum seismic response acceleration of the piping system decreased largely in the area surrounded by pipe elbows including the support structure which allowed plastic deformation. Furthermore, modal damping coefficient increased a maximum of about seven-fold. The increase ratio of the modal damping coefficient was proportional to the size of the effective mass ratio, when a relatively large increase was seen in the increase ratio of the modal damping coefficient. On the other hand, the amount of the initial stiffness of the support structure made a difference in the increasing tendency of the modal damping ratio. In the case of relatively small initial stiffness, the modal damping ratio of only one vibration mode increased. The increment of the modal damping ratio was proportional to the effective mass ratio in the case of large initial stiffness. In the viewpoint of the inelastic seismic design, the seismic response of the piping system was little affected by the plastic deformation of the support structure with 10% variation of the secondary stiffness to the initial stiffness. The result suggested that the seismic response of the piping system with the support structure can be estimated by using only the support model which has the elastic perfectly plastic property even if there are various shapes of steel type of support structures.

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.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

A validated robust and automatic procedure for vibration analysis of bridge structures using MEMS accelerometers

2020 ◽  
Vol 14 (3) ◽  
pp. 327-354
Author(s):  
Mohammad Omidalizarandi ◽  
Ralf Herrmann ◽  
Boris Kargoll ◽  
Steffen Marx ◽  
Jens-André Paffenholz ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Damping Ratio ◽  
Fem Analysis ◽  
Cost Effective ◽  
Analysis Procedure ◽  
Modal Parameters ◽  
Bridge Structure ◽  
Modal Damping ◽  
Mems Accelerometers ◽  
Better Than

AbstractToday, short- and long-term structural health monitoring (SHM) of bridge infrastructures and their safe, reliable and cost-effective maintenance has received considerable attention. From a surveying or civil engineer’s point of view, vibration-based SHM can be conducted by inspecting the changes in the global dynamic behaviour of a structure, such as natural frequencies (i. e. eigenfrequencies), mode shapes (i. e. eigenforms) and modal damping, which are known as modal parameters. This research work aims to propose a robust and automatic vibration analysis procedure that is so-called robust time domain modal parameter identification (RT-MPI) technique. It is novel in the sense of automatic and reliable identification of initial eigenfrequencies even closely spaced ones as well as robustly and accurately estimating the modal parameters of a bridge structure using low numbers of cost-effective micro-electro-mechanical systems (MEMS) accelerometers. To estimate amplitude, frequency, phase shift and damping ratio coefficients, an observation model consisting of: (1) a damped harmonic oscillation model, (2) an autoregressive model of coloured measurement noise and (3) a stochastic model in the form of the heavy-tailed family of scaled t-distributions is employed and jointly adjusted by means of a generalised expectation maximisation algorithm. Multiple MEMS as part of a geo-sensor network were mounted at different positions of a bridge structure which is precalculated by means of a finite element model (FEM) analysis. At the end, the estimated eigenfrequencies and eigenforms are compared and validated by the estimated parameters obtained from acceleration measurements of high-end accelerometers of type PCB ICP quartz, velocity measurements from a geophone and the FEM analysis. Additionally, the estimated eigenfrequencies and modal damping are compared with a well-known covariance driven stochastic subspace identification approach, which reveals the superiority of our proposed approach. We performed an experiment in two case studies with simulated data and real applications of a footbridge structure and a synthetic bridge. The results show that MEMS accelerometers are suitable for detecting all occurring eigenfrequencies depending on a sampling frequency specified. Moreover, the vibration analysis procedure demonstrates that amplitudes can be estimated in submillimetre range accuracy, frequencies with an accuracy better than 0.1 Hz and damping ratio coefficients with an accuracy better than 0.1 and 0.2 % for modal and system damping, respectively.

scholarly journals Estimation of Additional Equivalent Damping Ratio of the Damped Structure Based on Energy Dissipation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Xiuyan Hu ◽  
Qingjun Chen ◽  
Dagen Weng ◽  
Ruifu Zhang ◽  
Xiaosong Ren
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Theoretical Concept ◽  
Estimation Methods ◽  
External Excitation ◽  
Single Degree Of Freedom ◽  
Equivalent Damping ◽  
Seismic Motion ◽  
Practical Engineering ◽  
Energy Dissipation Capacity

In the design of damped structures, the additional equivalent damping ratio (EDR) is an important factor in the evaluation of the energy dissipation effect. However, previous additional EDR estimation methods are complicated and not easy to be applied in practical engineering. Therefore, in this study, a method based on energy dissipation is developed to simplify the estimation of the additional EDR. First, an energy governing equation is established to calculate the structural energy dissipation. By means of dynamic analysis, the ratio of the energy consumed by dampers to that consumed by structural inherent damping is obtained under external excitation. Because the energy dissipation capacity of the installed dampers is reflected by the additional EDR, the abovementioned ratio can be used to estimate the additional EDR of the damped structure. Energy dissipation varies with time, which indicates that the ratio is related to the duration of ground motion. Hence, the energy dissipation during the most intensive period in the entire seismic motion duration is used to calculate the additional EDR. Accordingly, the procedure of the proposed method is presented. The feasibility of this method is verified by using a single-degree-of-freedom system. Then, a benchmark structure with dampers is adopted to illustrate the usefulness of this method in practical engineering applications. In conclusion, the proposed method is not only explicit in the theoretical concept and convenient in application but also reflects the time-varying characteristic of additional EDR, which possesses the value in practical engineering.

Dynamic Response Analysis of Butt Joint of HTS-A Steel Considering Welding Residual Stresses

2013 ◽  
Vol 423-426 ◽  
pp. 944-950
Author(s):  
Wei Shen ◽  
Ren Jun Yan ◽  
Lin Xu ◽  
Kai Qin ◽  
Xin Yu Zhang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Dynamic Response ◽  
Hot Spot ◽  
Time History ◽  
High Strength ◽  
Simulation Method ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Response Analysis ◽  
Hull Structure

This paper uses both numerical simulation method and experimental research method to study on welding residual stress of high-strength steel of the cone-cylinder hull. Welding is often accompanied by a larger welding residual stress, which directly affects the safety and service life of the hull structure. In order to obtain the distribution of the welding residual stress, the welding procedure was developed by its parameter language by using FE analysis software in this paper. Then the welding residual stress of hot spot region was measured through X-ray nondestructive testing method, and compared it with simulation results. Finally, considering the residual stress as the initial stress, this paper analyzed dynamic response process of the welding structure under combined actions of the welding residual stress and multiaxial loads, which could more accurately determine the stress of welding structure and the location of fatigue risk point. According to the amplitude of damage parameters and strain time-history curve, we can estimate the fatigue life of structure by selecting the corresponding damage models.

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