RCM FEA Lateral Buckling Tool

Written by Martin Teigen.

The following is a presentation of a tool / platform / interface for performing in-place lateral buckling analysis of pipelines installed with residual curvature. The tool has been developed by Martin Teigen and Malik Ibrahim.

Overview

  • Pre-Processing:
    • Fully automated input file preparation for SIMLA or ABAQUS.
  • Post-Processing:
    • Formatting the relevant analysis results into a format that is understandable for the engineer, and visually presentable for reporting.
  • Facilitating for decision making:
    • Robust and easy to use tool
    • Reducing the effort in considering a great range of analysis configurations
    • This gives confidence in the design hence facilitating for decision making.
  • Relevant to a range of project phases:
    • Concept / pre-FEED: Evaluating feasibility. Simplified inputs.
    • FEED: Decision making, RCM as an alternative or not.
    • Detailed Design: Takes a level of input commonly applied in detailed design.
    • Follow-on engineering: Assessment of changed circumstances and unforeseen events.

Methodology

  • Methodology
    • Validated methodology from the peer-reviewed paper by Teigen and Ibrahim [OMAE2015].
    • Pipe (beam) elements.
    • Plastic material properties.
    • Residual strains resulting from installation loads are represented by bending the pipe.
    • Other ways of imposing the residual strains may offer higher accuracy, at the cost of efficiency. An example is simulating the entire reeling – un-reeling process.
  • Implementation
    • The inputs are specified in an Excel Spreadsheet.
    • Fully automated input file preparation via Python scripts (SIMLA)/ C# programming (ABAQUS).
    • Post-processing using Python.
    • The implementation is validated.

Validation

Three levels of validation:

  • Step 1: Comparison with an analytical solution.
    • Effective axial force μax * Wsub = 0.75 * 1194 [N/m] = 896 [N/m].
    • Slope corresponds with FE results.
  • Step 2: The FE Tool is validated against the peer-reviewed OMAE2015 paper by Teigen and Ibrahim.
    • Figure shows excellent correspondence.
  • Step 3: Validation between the two different tools for SIMLA and ABAQUS.
    • There are two independent FE Tools; one for SIMLA and one for ABAQUS.
    • These are implemented in two completely different programming languages; Python for SIMLA and C# for ABAQUS.
    • The two different tools yield the same results.
  • These are some examples, similar correspondence in the other results!

System Architecture

 

Features

Some examples of the features, and the associated input formats are presented below.

Pipeline Properties / Friction

  • Pipeline Properties / Friction
    • Different material properties and friction can be specified to sections along the pipeline

Model Discretisation

  • Model Discretisation
    • Efficient model discretisation allows for analysing large models with many imperfections.
    • No more elements than needed!

Seabed Bathymetry

  • Example 1: Residual curvature for freespan mitigation
  • Example 2: Residual curvature on a typical seabed.

              

Case Study

  • 14-inch OD, imperfection spacing 1000 m
  • Imperfections by under-straightening
  • Strain profile of Subsea 7’s Seven Oceans
  • Automated post-processed results.

 

Sensitivities

  • The engineer can explore the sensitivity of the following with the click of a button:
    • Diameter, WT, submerged weights, material properties, pipe-soil friction etc.
    • Discretisation
    • Loads: Temperature, pressure, load steps.
    • Residual curvature location along the pipeline, level of residual strain and the strain profile.
  • Robust tool that can easily perform sensitivities, reducing the effort in considering a great range of analysis configurations, hence giving confidence in the design and thereby facilitating for early decision making.

Summary and Overview

  • Tool for performing lateral buckling analysis using residual curvature as the control method.
  • ABAQUS automated input file generation, allows the engineer to focus on producing results instead of dealing with the complex code of input files.
  • Results of high quality in a short amount of time.
  • Validated implementation and methodology.
  • The automated process removes many complexities, giving the engineer the ability to complete the work efficiently – reducing cost.
  • Robust and easy to use tool, reducing the effort in considering a great range of analysis configurations, hence giving confidence in the design and thereby facilitating for early decision making.
  • The tool represents a significant amount of work, it has taken a long time to develop something that is not only functioning, but is robust.
  • Other ways of imposing the residual strains may offer higher accuracy, at the cost of efficiency.