Theoretical Formula for Determining the Maximum Straight Length of a Buried Pipeline That Can Prevent Seismic Buckling

2020 ◽  
Author(s):  
Shoma Onuki ◽  
Masaki Mitsuya
Keyword(s):  
Ground Motion ◽  
Design Method ◽  
Axial Stress ◽  
Theoretical Formula ◽  
Axial Loads ◽  
Buried Pipelines ◽  
Straight Pipe ◽  
Element Analysis ◽  
Pipe Length ◽  
Seismic Ground Motion

Abstract Buried pipelines must exhibit the appropriate seismic performance to be applied practically and securely. One major pipeline failure mode is buckling caused by seismic ground motion. Buckling typically occurs in straight pipeline sections because seismic axial loads mainly accumulate along straight lines. The design method for defining a maximum straight pipe length to decrease seismic axial loads is known to be effective in preventing buckling. Based on this previous knowledge, this study develops a theoretical formula for estimating the maximum straight length to prevent buckling. The proposed formula is derived using an analytical pipeline model with soil springs under seismic ground motion. Using this analytical model, the seismic loads which are applied to the straight pipe and the pipe connected to the straight pipe are calculated respectively. Then, the formula for the maximum straight length is derived by calculating the straight pipe length where the axial stress in the straight pipe is equal to the yield stress. The proposed formula is validated through finite element analysis. The maximum straight lengths obtained by the theoretical formula are in good agreement with FEM or shorter, thus providing a margin of safety. This work can be useful in designing buried pipelines to prevent buckling failures, thus enabling safer and more viable pipelines.

Beam-Mode Buckling of Buried Pipeline Subjected to Seismic Ground Motion

2012 ◽  
Author(s):  
Masaki Mitsuya ◽  
Takashi Sakanoue ◽  
Hiroyuki Motohashi
Keyword(s):  
Finite Element ◽  
Ground Motion ◽  
Critical Strain ◽  
Peak Load ◽  
Earthquake Resistance ◽  
Past Study ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Seismic Ground Motion ◽  
Beam Mode

During seismic events, buried pipelines are subjected to deformation by seismic ground motion. In such cases, it is important to ensure the integrity of the pipeline. Both beam-mode and shell-mode buckling may occur in the event of compressive loading induced by seismic ground motion. In this study, the beam-mode buckling of a buried pipeline that occurred after the 2007 Niigataken Chuetsu-oki earthquake in Japan is investigated. A simple formula for estimating the critical strain, which is the strain at the peak load, is derived, and the formula is validated by finite-element analysis. In the formula, the critical strain increases with the pipeline diameter and hardness of the surrounding soil. By comparing the critical strain derived in this study for beam-mode buckling with the critical strain derived in a past study for shell-mode buckling, the formula facilitates the selection of the mode to be considered for evaluating the earthquake resistance of a pipeline. In addition to the critical strain, a method to estimate the deformation caused by seismic ground motion is proposed; the method can be used to evaluate the earthquake resistance of buried pipelines. This method uses finite-element analyses, and the soil–pipe interaction is considered. This method is used to reproduce the actual beam-mode buckling observed after the Niigataken Chuetsu-oki earthquake, and the earthquake resistance of a buried pipeline with general properties is evaluated as an example.

Beam-Mode Buckling of Buried Pipeline Subjected to Seismic Ground Motion

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Masaki Mitsuya ◽  
Takashi Sakanoue ◽  
Hiroyuki Motohashi
Keyword(s):  
Finite Element ◽  
Ground Motion ◽  
Critical Strain ◽  
Earthquake Resistance ◽  
Past Study ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Seismic Ground Motion ◽  
Critical Buckling Strain ◽  
Beam Mode

During seismic events, buried pipelines are subjected to deformation by seismic ground motion. In such cases, it is important to ensure the integrity of the pipeline. Both beam-mode and shell-mode buckling may occur in the event of compressive loading induced by seismic ground motion. In this study, the beam-mode buckling of a buried pipeline that occurred after the 2007 Niigataken Chuetsu-oki earthquake in Japan is investigated. A simple formula for estimating the critical buckling strain, which is the strain at the peak load, is derived, and the formula is validated by finite-element analysis. In the formula, the critical buckling strain increases with the pipeline diameter and hardness of the surrounding soil. By comparing the critical strain derived in this study for beam-mode buckling with the critical strain derived in a past study for shell-mode buckling, the formula facilitates the selection of the mode to be considered for evaluating the earthquake resistance of a pipeline. In addition to the critical buckling strain, a method to estimate the deformation caused by seismic ground motion is proposed; the method can be used to evaluate the earthquake resistance of buried pipelines. This method uses finite-element analyses, and the soil–pipe interaction is considered. This method is used to reproduce the actual beam-mode buckling observed after the Niigataken Chuetsu-oki earthquake, and the earthquake resistance of a buried pipeline with general properties is evaluated as an example.

Three-Dimensional Nonlinear Seismic Ground Response Analysis of Local Site Effects for Estimating Seismic Behavior of Buried Pipelines

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Tsuyoshi Ichimura ◽  
Kohei Fujita ◽  
Muneo Hori ◽  
Takashi Sakanoue ◽  
Ryo Hamanaka
Keyword(s):  
Ground Motion ◽  
Large Scale ◽  
Three Dimensional ◽  
Response Analysis ◽  
Buried Pipelines ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Seismic Ground Motion ◽  
Local Site ◽  
Seismic Ground Response

Damage to buried pipelines caused by local amplification of seismic ground motion in highly nonuniform grounds is not yet fully understood. The development of methods to evaluate the amplification of ground motion in complex ground structures is thus desirable. Here, we report large-scale nonlinear seismic ground response analysis using a 3D nonlinear finite element method (FEM) and attempt to reproduce observed seismic ground motion. We also discuss the strain amplification processes and their effects on buried pipelines in detail. The findings are expected to aid in improving the seismic resistance of buried pipelines.

Investigation of the Influence of the Bourdon Effect on the Stress and Ovalization in Elbows

2014 ◽  
Author(s):  
Farzad M. Shemirani ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Michael Martens
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Maximum Stress ◽  
Oil And Gas ◽  
Design Parameters ◽  
Operating Pressure ◽  
Actual Situation ◽  
Straight Pipe ◽  
Element Analysis ◽  
Pipe Length

Elbows are used frequently in pipeline systems. Manufacturing of elbows tends to cause the primary circular sections to ovalize. Ovalization intensifies when elbows are subjected to internal hoop pressure. The total ovality in elbows comprises both manufacturing and pressurization ovality. Elbows with oval cross sections under internal pressure tend to straighten. This effect is called the Bourdon Effect. If these effects are not taken into consideration, unanticipated deformations and higher stress levels could be present at the location of elbows. The Canadian oil and gas pipeline code (CSA Z662-11) has limited the ovality in elbows to 3 and 6 percent for progressive and non-progressive ovalizations, respectively. A mere imposition of two limits cannot determine the safety factor of pipeline. Also, consequences of using elbows with large ovality remain ambiguous as well. Understanding the influence of the Bourdon Effect and ovalization on the elbow design parameters is required. In this paper, the influence of the Bourdon Effect on the stress and ovalization developed in the elbows are investigated. Four Nominal Pipe Sizes (12, 24, 36, and 42) are selected. Elbows and straight pipe segments connected to them are analyzed using Finite Element Analysis. Geometric dimensions of actual scanned pipeline elbows are used to represent the actual situation in the field. Under the operating pressure, the maximum stress, ovality, and the Bourdon Effect in elbows for different elbow thicknesses and straight pipe lengths connected to the elbows are monitored. In addition, in this paper, the effect of the initial ovality was investigated for NPS 24 with constant straight pipe length. It was shown that the increase or decrease in the final ovality of the pipe is dependent on the initial ovality of the elbow cross section.

Dynamic Characteristics of Base-Isolated Steel Frame under Seismic Ground Motion

2011 ◽  
Vol 255-260 ◽  
pp. 2341-2344
Author(s):  
Mohammad Saeed Masoomi ◽  
Siti Aminah Osman ◽  
Ali Jahanshahi
Keyword(s):  
Ground Motion ◽  
Base Isolation ◽  
Time History ◽  
Steel Structure ◽  
Steel Structures ◽  
Steel Frame ◽  
Nonlinear Time History Analysis ◽  
Seismic Load ◽  
Vector Method ◽  
Seismic Ground Motion

This paper presents the performance of base-isolated steel structures under the seismic load. The main goals of this study are to evaluate the effectiveness of base isolation systems for steel structures against earthquake loads; to verify the modal analysis of steel frame compared with the hand calculation results; and development of a simulating method for base-isolated structure’s responses. Two models were considered in this study, one a steel structure with base-isolated and the other without base-isolated system. The nonlinear time-history analysis of both structures under El Centro 1940 seismic ground motion was used based on finite element method through SAP2000. The mentioned frames were analyzed by Eigenvalue method for linear analysis and Ritz-vector method for nonlinear analysis. Simulation results were presented as time-acceleration graphs for each story, period and frequency of both structures for the first three modes.

scholarly journals Electromagnetic-Thermal Integration Design of Permanent Magnet Motor for Vehicles

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Shijun Chen ◽  
Qi Zhang ◽  
Surong Huang
Keyword(s):  
Permanent Magnet ◽  
High Performance ◽  
Design Method ◽  
Electromagnetic Properties ◽  
Permanent Magnet Motor ◽  
Element Analysis ◽  
Experiment Platform ◽  
Motor Design ◽  
Dimensional Parameters ◽  
Thermal Integration

To more efficiently design high performance vehicular permanent magnet motor, an electromagnetic-thermal integration design method is presented, which considers both the electromagnetic properties and the temperature rise of motor winding when determining the main dimensional parameters of the motor. Then a 48-slot and 8-pole vehicular permanent magnet motor is designed with this method. The thermomagnetic coupling design is simulated and validated on the basis of multiphysical domain on finite element analysis. Then the prototype is analyzed and tested on a newly built motor experiment platform. It is shown that the simulation results and experimental results are consistent, which validate the accuracy and effectiveness of the new design method. Also this method is proved to well improve the efficiency of permanent magnet motor design.

Design Research of Steel Pipe Combination of Angle Steel Tower of XiYue 220kV Cross Section

2013 ◽  
Vol 470 ◽  
pp. 408-411 ◽  
Author(s):  
Yan Zhong Ju ◽  
Xiao Xu Fu ◽  
Neng Xian Zeng
Keyword(s):  
Finite Element Analysis ◽  
Cross Section ◽  
Design Research ◽  
Axial Stress ◽  
Steel Pipe ◽  
Stress Difference ◽  
Analysis Software ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Angle Steel

Given the path situation of Xiyue substation 220kV four outlets project crossing Shunde waterway section,this article applies of Dao Heng tower full stress analysis software and the finite element analysis software ANSYS to two steel pipe combination of angle steel towers to carry on design research,contrast axial stress of two kinds of software,analyse the reasons of axial stress difference.

EXPERIMENTAL STUDY ON FLAME PROPAGATION IN A STRAIGHT PIPE

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Siti Zubaidah Sulaiman ◽  
Rafiziana Md Kasmani ◽  
A. Mustafa
Keyword(s):  
Experimental Study ◽  
Flame Propagation ◽  
Experimental Work ◽  
Diameter Ratio ◽  
Straight Pipe ◽  
Pipe Length ◽  
Operating Condition ◽  
Consistent Trend ◽  
Length To Diameter Ratio

Flame propagation in a closed pipe with diameter 0.1 m and 5.1 m long, as well as length to diameter ratio (L/D) of 51, was studied experimentally. Hydrogen/air, acetylene/air and methane/air with stoichiometric concentration were used to observe the trend of flame propagation throughout the pipe. Experimental work was carried out at operating condition: pressure 1 atm and temperature 273 K. Results showed that all fuels are having a consistent trend of flame propagation in one-half of the total pipe length in which the acceleration is due to the piston-like effect. Beyond the point, fuel reactivity and tulip phenomenon were considered to lead the flame being quenched and decrease the overpressures drastically. The maximum overpressure for all fuels are approximately 1.5, 7, 8.5 barg for methane, hydrogen, and acetylene indicating that acetylene explosion is more severe. 

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