Analysis of ERDIP joint at fault using Abaqus - A case study for simulation based product qualification

ANALYSIS OF ERDIP JOINT AT FAULT USING ABAQUS –
A CASE STUDY FOR SIMULATION BASED PRODUCT
QUALIFICATION
Dr. A. Chakraborty, Dr. S. Srigiriraju, Dr. B. Ozturk
Virtual Integrated Analytics Solutions (VIAS)
Jeff Mason
US-PIPE
October 25, 2018
1400 Broadfield Blvd. Suite 325, Houston TX 77084
Phone : +1 (832) 301-0881
www.viascorp.com
Contact Person: Dr. A. Chakraborty – achakraborty@viascorp.com

© 2018 Virtual Integrated Analytics Solutions Inc.
Agenda
2
• VIAS Introduction
• Background & Objective - need for FEA in Earthquake Resistant Ductile Iron
Pipe (ERDIP) design
• Methodology
➢ Validation of FEA
➢ Compliance with design criteria
• Validation of FEA using 6” diameter ERDIP joints
➢ Bending, axial compression and tension, shear
• Design check using FEA for 48” diameter ERDIP joints
➢ Joints and soil-pipe interaction modeled as nonlinear springs
➢ Two fault scenarios
• Conclusions & Value proposition

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3

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➢ Systems Development and Integration
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4

Simulation Capabilities
Design Analysis and
Validation using Simulation
Fatigue & Durability /
Fracture / Damage
Mechanics
Optimization and Reliability
Multi-physics Simulations
(CFD, Thermal Analysis)
FFS and Code Based Design
by Analysis
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Modelling
Structural Analysis / Plant
Engineering
Crack Propagation Modelling
Simulation Automation
Verification and Validation
Local-Global Modeling
5

Background
7
Damaged Buried Pipeline due to Earthquake
2002 Denali Fault Quake - 14 feet horizontal and 2.5
feet vertical ground movement
For buried pipe more innovative solution is needed at the joint

Background
8
• ERDIP – Earthquake Resistant Ductile Iron Pipe
• ERDIP joints through their extension, contraction
and deflection minimize the rupture of pipeline
during earthquakes
• Client previously conducted physical qualification
testing for small diameter pipeline (i.e. simpler
experimental testing)
• High cost of physical testing for large diameter pipe
hindering development (complex testing may not
even be possible)
• Regulator agreed to accept results from a validated
FEA methodology in lieu of physical testing Courtesy – US-Pipe

FEA – Value Proposition for Qualification
9
• VIAS conducted FEA qualification of proprietary connections to verify
that they meet design criteria in a seismic event scenario
• FEA based product development and approval:
EXISTING
TESTING
(<< dia)
FEA
METHODOLOGY
VALIDATION
NEED DRIVEN
FEA (>> dia)
EVALUATE
DESIGN
CRITERIA
LOCAL-GLOBAL
APPROACH
Local: joint stiffness
Global: soil-pipe interaction
✓ Cost effective,
✓ Quick design variations,
✓ What-if scenarios,
✓ Better insight into the
joint behavior,
✓ Ease of doing local and
global,
✓ Introduce complexity
successively

Objective of Project
10
• Develop and validate FEA methodology using previous experimental
results for 6” diameter pipeline.
• Use the validated FEA methodology to verify if two types of ERDIP
joints (Type-1 & Type-2) pass the following design criteria in specific
fault (right-lateral shift) scenarios for 48” diameter pipeline:
➢ Maximum Axial Displacement – 6” (Type-1), ~0” (Type-2)
➢ Maximum Deflection Angle – 15° (Type-1), 0.5° (Type-2)
➢ Axial Load without Leakage – 822 kips
➢ Allowable Stress – 40.5 ksi for both joints and the pipes (based
on proportional limit)
Type 2Type 1

12
• FEA simulations to develop analytical
non-linear equivalent springs for the
joint assembly to capture behavior:
➢ Bending resistance
➢ Capacity assembly under direct
tension and compression
➢ Shear resistance
• Save time by eliminating the need for
a full 3D FEA model for joints
Shear Spring
Axial Spring
Rotational Spring
Reduced-Order Modelling of Joint
Pipeline
Pipeline
Equivalent Springs for Joint Behavior (LOCAL)

Soil Axial
Spring
Soil Transverse
Spring
Pipe-Joint Springs
13
• Develop analytical bi-linear soil springs to
capture behavior of soil during interaction:
➢ Axial direction
➢ Transverse direction
• Stiffness is proportional to nodal area of
contact. Stiffness at joint scaled to half the
stiffness at pipe
• Gradually built up complexity allows for
traceability of potential errors
Reference for Approach - “Research of Earthquake Resistant Ductile
Iron Pipe (ERDIP) for fault crossing,” K. Oda, et al., Kubota Corporation.
Incorporating Soil-Pipe Interaction
Representative Bi-Linear Behavior
Pipeline Pipeline
Equivalent Springs for Soil-Pipe Interaction (GLOBAL)

14
• Three loading tests used to compare physical tests and FEA:
➢ Bending
➢ Tension and compression
➢ Shear
FEA Model Setup of 4-point Bending Test (LOCAL)
4-Point Bending Test Experimental Setup
Validation of FEA Using Test Results of 6” Diameter
Pipeline

15
• Develop equivalent joint and soil springs in FEA
• Use the springs in FEA, to verify if 48” diameter pipeline with two types
of ERDIP joints will satisfy the design criteria for two crossing angles
between pipe and fault:
➢ 90°
➢ pipe azimuth 90° and fault orientation azimuth 66°
GLOBAL Model of the PipelinePipe and Fault Orientation
Simulation of Seismic Event: Design Check for 48”
Diameter Pipeline

VALIDATION OF METHODOLOGY
USING SMALL DIAMETER PIPE
JOINTS

17
FEA Model: Mesh and Material
• About ~120,000 elements
• Ductile iron material property used for
components and pipe
• Elastic-Plastic material properties
Meshed Assembly
General Assembly
Lock Rings
Bell End
Spigot End

Test 1: 4-point Bending
18
• Tests were conducted on 2 different
orientations of the joint (Test A and Test B)
• Simulation results showed stiffer response
than the physical tests
• During the physical tests, fracture failure
occurred as the deflection angle reached
about 9°
• A crack may possibly have initiated early
in the test giving a lower bending
resistance in the physical tests.
θ
Lock Ring Alignments for Test A & B
Deflection Angle

19
Test 2: Axial Compression and Tension
• Simulation results showed stiffer response
than the physical tests
• A local yielding event in physical tests gave a
lower resistance in both tensile and
compressive loads
Axial Load Application

20
Test 3: Shear
• Physical test results unavailable
• Simulation results validated by engineering
judgement
Shear Load Application

21
Test 4: Pipe-Soil Interaction at Fault
• Simplified soil model used
• Peak axial forces match
Beam Model with Soil-Spring

DESIGN VERIFICATION OF
LARGE DIAMETER PIPELINE
USING FEA

23
Large Diameter Pipe Joint

24
Large Diameter Pipe Joint (Mesh)
Element Type No. of Elements
C3D8R (Linear Hexahedral) 36,750
C3D4 (Linear Tetrahedral) 6,643
R3D4 (Linear Quadrilateral) 44
C3D6 (Linear Wedge) 1,770
Total Elements 45,207
Element Type No. of Elements
C3D8R (Linear Hexahedral) 30,190
C3D4 (Linear Tetrahedral) 2,894
R3D4 (Linear Quadrilateral) 44
C3D6 (Linear Wedge) 120
Total Elements 40,367

25
Type-1 Joint: Equivalent Springs
Generate spring behavior through 4 FEA runs: bending, axial compression,
axial tension, and shear

26
Type-2 Joint: Equivalent Springs
Generate spring behavior through 4 FEA runs: bending, axial compression,
axial tension, and shear

𝐾1 =
𝜋𝐷𝛾 ℎ + 0.5𝐷 1 + 𝐾0 tan ∆
2𝛿1
𝐾2 = 7𝑥10−7
𝐾1
𝐾𝑡1 = 𝐾𝐷 𝐾𝑡2 = 1. 8𝑥10−6
𝐾𝑡1
D : Diameter of the pipe (48”)
𝛾: Soil unit weight (120 lb/ft3)
h : Burial depth (5 ft)
K0: Coefficient of lateral soil pressure
at rest
Δ: Internal friction angle (34o)
δ1: Inflection point of axial deflection
spring (0.019685” from Reference)
K: Subgrade reaction modulus
(215338 pcf from Reference)
27
Soil Spring Stiffnesses
Axial Spring
Transverse Spring
Reference: “Research of Earthquake Resistant Ductile Iron Pipe (ERDIP) for fault crossing,” K. Oda, et al., Kubota
Corporation.
The slope of curve beyond the first linear portion is arbitrarily chosen to be small
factor of the slope of the first linear portion

28
FEA Pipeline Model with Fault Orientations &
Locations
• Joint and soil springs modeled as
Cartesian connectors with behavior
• Pipeline modeled as pipe elements
3 locations for fault at 90o
Same locations for fault at 66o
Connector Locations
Fault at Connector Type-1
Fault at Connector Type-2
Fault Between Connectors

29
FEA Results for Loading Scenarios
Deformation, 48” Pipe, Seismic Event at 66o
(animation)

30
• Verification with certified design capacity:
• Failure refers to not meeting one or more certification criteria set by the regulator:
axial displacement or deflection angle
Fault Location Joint Type Fault 90o Fault 66o
Axial Rotation Axial Rotation
At Type-1 joint
Type-1 Pass Pass Fail Pass
Type-2 Pass Fail Fail Fail
At Type-2 joint
Type-2 Pass Pass Fail Fail
Between 2 joints
Type-2 Pass Fail Fail Fail

31
• No local yield or high axial load leading to leakage in all the loading scenarios for both
fault orientations
Using FEA one can show integrity of the joint, and that may help relaxing a preset
certification criteria:
1. Joint can be re-designed and tested in FEA to meet the design criteria unlike in
physical tests.
2. Design criteria can also be tweaked once we have confidence from FEA tests of
the joints as seen in this case.
Von Mises Stress, 48” Pipe Bending (animation)

32
FEA Results for Pipeline with Different Soil Weight
• Additional sensitivity study to account for concrete embedment
• Soil weight reduced to 100lb/ft3
• Reduces the axial and transverse soil spring stiffness
• Only one loading scenario studied: Fault at 66o located at Type-1 joint:
Joint Axial Rotation
Type-1 Fail Pass
Type-2 Fail Fail

33
FEA Results for Pipeline with Polywrap
• Polywrap protects the pipeline from corrosion
• 75% friction coefficient between soil and pipeline assumed due to
polywrap
➢ Axial soil spring stiffness reduces by 30%. Transverse soil spring
stiffness is unaffected.
• Only one loading scenario studied: Fault at 66o located at Type-1 joint:
Joint Axial Rotation
Type-1 Fail Pass
Type-2 Fail Fail

34
Conclusion & Value Proposition
➢ FEA methodology validated for ERDIP joint behavior
➢ Simplified FEA model with equivalent springs for joints and soil-pipe interaction
used for design criteria checks
➢ Demonstrates to the regulatory body that FEA can be used as a valid methodology
in lieu of physical tests
➢ Easy to study the effects of extraneous factors like soil weight, polywrap, etc. very
quickly using FEA
➢ FEA workflow can be applied for many applications where one needs to combine
local-global response for pipeline

35
Thank you

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