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Research Papers: Materials and Fabrication

Fatigue Stress Evaluation at Shell-to-Bottom Joint With Double Plastic Hinge in Elevated Temperature Steel Tanks on Concrete Ring Walls

[+] Author and Article Information
Sridhar Sathyanarayanan

Faculty of Engineering and Applied Science,
Memorial University of Newfoundland,
St. John's, NF A1B 3X5, Canada
e-mail: ssridhar@mun.ca

Seshu M. R. Adluri

Faculty of Engineering and Applied Science,
Memorial University of Newfoundland,
St. John's, NF A1B 3X5, Canada
e-mail: adluri@mun.ca

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received August 16, 2012; final manuscript received March 13, 2014; published online February 23, 2015. Assoc. Editor: Marina Ruggles-Wrenn.

J. Pressure Vessel Technol 137(4), 041408 (Aug 01, 2015) (8 pages) Paper No: PVT-12-1130; doi: 10.1115/1.4027202 History: Received August 16, 2012; Revised March 13, 2014; Online February 23, 2015

The shell-to-bottom joint of hydrocarbon storage tanks is a critical location which may experience fatigue cracking and requires evaluation of the local cyclic stresses especially in the case of elevated temperature tanks. The fill/draw down cycle of the stored liquid causes low cycle fatigue near this joint and hence a fatigue evaluation is recommended. The peak alternating stress at this location, used to enter the fatigue curves is currently determined using a pseudo-elastic analysis that represents strain range due to inelastic deformations. API 650 employs beam on elastic foundation theory for this analysis. This theory is being used for tanks resting fully on earthen foundation as well as those on concrete ring wall. This paper studies the validity of using this theory for tanks with concrete ring wall foundation which are much more rigid compared to earthen foundations. Some of the difficulties in the current practice are highlighted. An alternative to the current model is presented for the determination of stresses in such tanks. The results are validated using finite element analysis. The results show that the current practice needs to be revised or rejustified in an alternative manner.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Shell-to-bottom joint in the tank with ring wall foundation

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Fig. 2

Slope in the shell at the bottom joint

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Fig. 3

Uplift at shell-to-bottom joint of a tank on concrete ring wall [12]

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Fig. 4

Target element geometry (ansys)

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Fig. 5

Typical plane element axisymmetric mesh

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Fig. 6

Dimensions of tank used for finite element analysis

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Fig. 7

Uplift of bottom plate and stresses using nonlinear FE model with plane elements

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Fig. 8

Idealized beam model

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Fig. 9

Uplift deformation of bottom plate

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Fig. 10

Uplift deformation from FE model with shell elements

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Fig. 11

Radial stress in bottom plate along the radius

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Fig. 12

Bending and von Mises stress in 6 mm thick bottom plate (on the inside)

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Fig. 13

Bending (radial) stress in 6 mm bottom plate (on the outside)

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Fig. 14

Bending and von Mises stress in 8 mm thick bottom plate (on the inside)

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Fig. 15

Bending of bottom plate at shell-to-bottom joint [11]

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Fig. 16

Influence of bottom moment on tank wall bending stresses

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