SC SOLUTIONS, Inc. © 2014, CONFIDENTIAL SC SOLUTIONS, Inc. © 2017

DOE NPH Meeting

Fluid-Soil-Structure Interaction Analysis of Tank for Seismic Evaluation of Nozzle Subjected to Differential Movement

October 23, 2018

LA-UR-18-29880

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Problem Statement

2

• Seismically qualified critical storage tanks

• Nonlinear anchor response

• Founded on soft soil with stiffness reversals

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Problem Statement

3

DNFSB concern:

– Over-restrained pipe-tank connection

– SAM-induced stress at connection

TANK

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Previous Analysis

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Max soil displacement + allowable anchor elongation

Δdemand = Δrocking + εallow·lbolt induced on tank end of system

1% strain

Δrocking

Δdemand

Concluded nozzle significantly overloaded

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Project Scope

5

Assess functionality (pressure retention) of tank and draw-off piping connection during and after DBE

Phase 1: Determine if detailed analysis can address concern

Phase 2: Perform final analysis and documentation to full code and QA requirements for support of safety basis

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Acceptance Criteria

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• No failure of tank shell at piping connection

– API 650 moment capacity

– AWWA allowable stress

• No failure of draw-off piping at connection

– ASME B31E

• No local tank failure caused by anchor behavior

– SQUG GIP 3A

– Elongation limit ~1%

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Global System Model

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Global System Model

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Soil Model

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• Equivalent linear properties

• Visco-elastic material model

• 400x400x500 ft. soil domain

• Single soil profile

• Single time history

• Lysmer damper

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Soil Verification

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Fluid-Structure Model

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• Tank shell elements (w/ beam elements)

• Fluid continuum elements

• Lagrangian fluid model

• Fluid constrained w/in tank:

• Horizontally along wall

• Vertically across base

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Nonlinear Anchor Model

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Nut

Free

Tension-only spring

Elastic-plastic anchor

Contact surface

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Nonlinear Anchor Response

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Model Verification

• Site response analysis deconvolution

• Finite element soil model site response

• Fluid model static and modal response

• Nonlinear anchor behavior

• Nozzle response due to uplift

• System behavior in sensitivity studies

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Response at Maximum Nozzle Stress

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5x magnification, with fluid

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Response at Maximum Nozzle Stress

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50x magnification, without fluid

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System Response

17

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Tank Dynamic Response

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Nozzle demands driven by:

• Fluid convection

• Fluid stress (impulse)

• Tank rocking and uplift

• Local tank – nozzle deformation

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Tank Dynamic Response

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Nozzle demands driven by:

• Fluid convection

• Fluid stress (impulse)

• Tank rocking and uplift

• Local tank – nozzle deformation

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Tank Dynamic Response

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Nozzle demands driven by:

• Fluid convection

• Fluid stress (impulse)

• Tank rocking and uplift

• Local tank – nozzle deformation

Uplift

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Tank Dynamic Response

21

Nozzle demands driven by:

• Fluid convection

• Fluid stress (impulse)

• Tank rocking and uplift

• Local tank – nozzle deformation

X=Diff Disp.

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Tank Dynamic Response

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15 15.5 16 16.5 17 17.5 18 18.5 19

Forc

e /

Mo

men

t

Time, s

Forces at Tank Wall

Y moment, k*in

Axial force, k

Vertical force, k

Uplift-driven

Axial-driven

Uplift-driven

axial+uplift driven axial+uplift driven

Nozzle demand

Axial response

Uplift response

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Tank Dynamic Response

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1. Tank rocking and uplift contribution weaker than

anticipated

2. Local tank longitudinal differential displacement observed

3. Overall maximum stress due to combined behavior

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Sensitivity Studies

Purpose: Confirm behavior, inform Phase 2

Varied Parameters:

• Stiff anchors

• Reduced water height

• 1st pipe support removed

• Longitudinal support removed

• Time history variability

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Benefits of Detailed Analysis

• Nozzle moments roughly 1/3

• Reduced tank displacement due to SSI rocking effect

• Combined FSI-SSI-nonlinear anchor response explicitly captured

• Local tank deformation a result of combined system response vs. imposed boundary conditions

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Project Conclusion

• Functionality controlled by tank shell stress

• Anchor strain close to recommended limit

• Tank experienced minor overstress

– ~10% above yield stress, half of tensile stress

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Detailed analysis likely to address concern given acceptability of minor overstress

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Questions?

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