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.

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

Numerical Study on Inelastic Seismic Design of Piping Systems Using Damping Effect Based on Elastic–Plastic Property of Pipe Supports

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Akira Maekawa ◽  
Tsuneo Takahashi
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Plastic Property ◽  
Damping Coefficient ◽  
Seismic Load ◽  
Piping System ◽  
Elastic Plastic ◽  
Damping Effect ◽  
Modal Damping ◽  
Piping Systems

This study describes inelastic seismic design of piping systems considering the damping effect caused by elastic–plastic property of a pipe support which is called an elastic–plastic support. Though the elastic–plastic support is proposed as inelastic seismic design framework in the Japan Electric Association code for the seismic design of nuclear power plants (JEAC4601), the seismic responses of the various piping systems with the support are unclear. In this study, 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 elastic–plastic support was investigated 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 elastic–plastic support which allowed plastic deformation. The modal damping coefficient increased a maximum of about sevenfold. Furthermore, the amount of the initial stiffness of the elastic–plastic support made a difference in the increasing tendency of the modal damping coefficient. From the viewpoint of the support model in the inelastic seismic design, the reduction behavior for the seismic response of the piping system was little affected by the 10% variation of the secondary stiffness. These results demonstrated the elastic–plastic support is a useful inelastic seismic design of piping systems on the conditions where the design seismic load is exceeded extremely.

Analytical Study on Effect of Failure of Pipe Support Structure on Seismic Response of Piping System

2013 ◽  
Author(s):  
Tsuneo Takahashi ◽  
Akira Maekawa
Keyword(s):  
Plastic Deformation ◽  
Seismic Response ◽  
Seismic Load ◽  
Piping System ◽  
Displacement Curve ◽  
Initial Stiffness ◽  
Support Structure ◽  
Plastic Model ◽  
Plastic Deformation Behavior ◽  
Load Displacement

This study discussed seismic response of a piping system when the pipe support structure was deformed plastically on being subjected to a much larger seismic load than the designed one. This case is expected as one of the conditions beyond seismic design that should be analyzed. To examine the effect of elastic-plastic deformation of the pipe support structure on seismic response, the effect of various shapes and failure mode of support structures was investigated. Difference of failure modes of the pipe support structure was modeled by change of initial stiffness and secondary stiffness of the load-displacement curve in this study. Seismic response analyses were conducted by using a typical small bore piping system shaped in a three-dimensional arrangement. The investigated change of seismic response behavior generated by plastic deformation of the pipe support structure was clarified based on comparison of seismic responses by using the elastic-fully plastic model and bi-linear model with various initial stiffness and secondary stiffness values. The results showed that the secondary stiffness of the load-displacement curve of the support structure did not affect the decreasing area of the response acceleration and the amount of the decrement significantly. It was concluded that the plastic deformation behavior of the pipe support structure could be modeled by using the elastic-fully plastic model when modeling plastic deformation characteristics of the pipe support structure.

Damping of Stay Cable-Passive Damper System with Effects of Cable Bending Stiffness and Damper Stiffness

2012 ◽  
Vol 204-208 ◽  
pp. 4513-4517 ◽  
Author(s):  
Min Liu ◽  
Guang Qiao Zhang
Keyword(s):  
Numerical Analysis ◽  
Damping Ratio ◽  
Bending Stiffness ◽  
Damping Coefficient ◽  
Stay Cable ◽  
Modal Damping Ratio ◽  
Passive Damper ◽  
Modal Damping ◽  
Optimal Damping ◽  
Coefficient Increase

In the present paper, the asymptotic solution of modal damping ratio of stay cable-passive damper system with the influence of cable bending stiffness and damper stiffness was derived. Maximum modal damping ratio and corresponding optimal damping coefficient, which indicated the relationships of the characteristics of the damper and the cable bending stiffness was theoretically analyzed to obtain their close solutions. On the basis of these close solutions, numerical analysis of modal damping of stay cable-passive damper system with the effects of cable bending stiffness and damper stiffness was conducted. The numerical and analytical results show that the maximum modal damping ratio decrease and the corresponding damping coefficient increase, when considering the influence of the damper stiffness and the cable bending stiffness.

Impact of Deformation Stiffness Beyond Yield Point of Pipe Support Structures on Nonlinear Seismic Response Analysis

2014 ◽  
Author(s):  
Tsuneo Takahashi ◽  
Akira Maekawa
Keyword(s):  
Plastic Deformation ◽  
Seismic Response ◽  
Safety Evaluation ◽  
Response Analysis ◽  
Seismic Load ◽  
Piping System ◽  
Support Structures ◽  
Seismic Response Analysis ◽  
Support Structure ◽  
Nonlinear Seismic Response

The importance of safety evaluation for beyond design conditions has come to be required since the accident at the Fukushima Daiichi Nuclear Power Plant as a consequence of the Great East Japan Earthquake. Real simulations of seismic response for the plant structures and components enhance establishment of reasonable design margins and safety evaluation criteria in a situation beyond design-basis accidents. For piping systems, nonlinear seismic response analysis considering plastic deformation of pipe support structures can lead to a safety evaluation based on more rational input values. This study discussed seismic response of a piping system and its appropriate analysis method when a plastically deformable pipe support structure was subjected to a much larger seismic load than the designed one. Seismic response analyses of the piping system including a plastically deformable pipe support structure were conducted for various input acceleration levels. The vibration characteristics, response acceleration, and moment of piping were compared in relation to the amount of plastic deformation of the pipe support structure. As a result of the comparisons, a support model with the elastic fully plastic property was proposed as a simple and proper method to calculate the seismic response of the piping system considering the plastic deformation of the pipe support structure.

scholarly journals Sensitivity of the Viscous Damping Coefficient of Carbon Fiber in Carbon-Fiber-Reinforced Plastic with Respect to the Fiber Angle

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 781
Author(s):  
Chan-Jung Kim
Keyword(s):  
Carbon Fiber ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Viscous Damping ◽  
Fiber Reinforced Plastic ◽  
Fiber Angle ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Reinforced Plastic ◽  
Derivatives Of

The variation in the viscous damping coefficient with the carbon fiber angle can be evaluated using the partial derivatives of the viscous damping coefficient with respect to the resonance frequency and modal damping ratio. However, the direct derivatives of the viscous damping coefficient were not effective solutions to the sensitivity analysis of carbon-fiber-reinforced plastic (CFRP) structures because the viscous damping from the binding matrix was not changed over the carbon fiber angle. If the identified viscous damping coefficients were assumed to be equivalent values from the parallel relationship between the binding matrix and carbon fiber, the relative error of the viscous damping coefficient of carbon fiber between the increased carbon fiber angle and reference angle could be used as the sensitivity index for the viscous damping coefficient of carbon fiber only. The modal parameters, resonance frequency, and modal damping ratio were identified from the experimental modal test of rectangular CFRP specimens for five different carbon fiber angles between 0° and 90°. The sensitivity of the viscous damping coefficient of carbon fiber was determined for two sensitivity indices: the direct derivative of the mass-normalized equivalent viscous damping coefficient and the relative error of the viscous damping coefficient of carbon fiber. The sensitivity results were discussed using the five mode shapes of the CFRP specimen, that is, three bending modes and two twisting modes.

Pulsation suppression in a reciprocating compressor piping system using a two-tank element

2017 ◽  
Vol 232 (4) ◽  
pp. 427-437 ◽  
Author(s):  
Quyang Ma ◽  
Zhenhuan Wu ◽  
Guoan Yang ◽  
Yue Ming ◽  
Zheng Xu
Keyword(s):  
Theoretical Model ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Wave Theory ◽  
Damping Coefficient ◽  
Piping System ◽  
Pressure Pulsations ◽  
Surge Tank ◽  
Piping Systems ◽  
Gas Pulsations

Gas pulsations excited by reciprocating compressors could introduce severe vibrations and noise in piping systems. When pulsating gas flows through the reducers, the changes in flow characteristics, such as velocity and damping coefficient, will affect the pressure pulsations. To circumvent these constraints, a two-tank element is introduced to control the gas pulsation that is still strong in the piping system with a surge tank. Installing another surge tank to form a two-tank element is more flexible and costs lower than replacing the original surge tank with a larger one. In this work, a theoretical model based on the wave theory was proposed to study the transferring mechanism of gas pulsations in the pipeline with the two-tank element. By considering the damping coefficient and the Mach number, the distributions of the pressure pulsations were predicted by the theoretical model and agreed with the three-dimensional fluid dynamics transient analysis. Three experiments were conducted to prove that the suppression capability of the two-tank element is as good as that of a single-tank element (surge tank) with the same surge volume. The volume optimization of the two-tank element is implemented by selecting the best allocations of the two tanks’ volumes to achieve larger reductions of pressure pulsations. Assuming that the total surge volume is constant, we found that the smaller the volume of the front tank (near the cylinder) is, the lower the pulsation levels are. The optimized result proves that in some conditions the two-tank element could control pulsations better than the single-tank element with the same surge volume.

Modal damping ratio analysis of dynamical system with non-stationary responses

2016 ◽  
Vol 59 ◽  
pp. 138-146 ◽  
Author(s):  
Da Tang ◽  
Ran Ju ◽  
Qianjin Yue ◽  
Shisheng Wang
Keyword(s):  
Dynamical System ◽  
Damping Ratio ◽  
Ratio Analysis ◽  
Modal Damping Ratio ◽  
Modal Damping

scholarly journals Coupling of Flexural and Longitudinal Damped Vibration in a Two-Layered Beam

1998 ◽  
Vol 5 (5-6) ◽  
pp. 337-341
Author(s):  
F. Pourroy ◽  
S. Shakhesi ◽  
P. Trompette
Keyword(s):  
Damping Ratio ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Layered Beam ◽  
Flexural Vibrations

In dynamics, the effect of varying the constitutive materials’ thickness of a two-layered beam is investigated. Resonance frequencies and damping variations are determined. It is shown that for specific thicknesses the coupling of longitudinal and flexural vibrations influences the global modal damping ratio significantly.

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