Seismic Engineering

Seismic Behavior of a Single Deck Floating Roof Due to Second Sloshing Mode

[+] Author and Article Information
Mohammad Ali Goudarzi

Structural Engineering Research Center
International Institute of Earthquake
Engineering and Seismology (IIEES)
No. 21, Arghavan Street
North Dibajee, Farmanieh
Tehran 11369, Iran
e-mail: m.a.goodarzi@iiees.ac.ir

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received November 27, 2011; final manuscript received June 17, 2012; published online December 17, 2012. Assoc. Editor: Spyros A. Karamanos.

J. Pressure Vessel Technol 135(1), 011801 (Dec 17, 2012) (6 pages) Paper No: PVT-11-1216; doi: 10.1115/1.4007291 History: Received November 27, 2011; Revised June 17, 2012

Second mode sloshing motion induces the vertical out-of-plane deformation of deck plate in single deck floating roof (FR) cylindrical storage tanks. This vertical deformation tends to shrink the deck plate in horizontal direction, causing elliptical deformation of pontoon. In order to evaluate seismic stress caused by the second sloshing mode, the relation between out-of-plane vertical deformation of deck plate and the radial shrinkage of pontoon is required. In this study, a simple analytical approach is proposed for calculating the shrinkage of the pontoon. The numerical analysis is also performed for five tanks with various dimensions to assess the effectiveness of introduced new method. The accuracy of proposed formulation is confirmed by comparing its results with the results of both numerical analysis and available experimental measurements. Despite existing empirical formula, geometric characteristics of considered tanks are involved in proposed formulation and it is shown that final relationship could be utilized for various ranges of tank dimensions without scaling or unit limitation. It is also found from the results of numerical analysis that the dynamic characteristics of sloshing modes are not considerably affected by the presence of floating roof.

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Fig. 1

Elliptical deformation of pontoon caused by the second sloshing mode in SDFR

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Fig. 2

Second sloshing mode shape for the tank without FR

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Fig. 3

Schematic deformation of SDRF during the second sloshing mode

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Fig. 4

Finite element model of SDFRT

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Fig. 5

Second mode shape of tank 1

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Fig. 6

Elliptical deformation of pontoon (Tank 2, R = 39 m, ΔmR = 2.35 m)

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Fig. 7

Membrane stress of deck plate in X direction (Tank 2, R = 39 m, ΔmR=2.35 m)

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Fig. 8

Relationship between radial contraction and out-of-plane deformation of deck obtained from FEM analysis, proposed formula (Eq. (17)) and empirical Eq. (6).

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Fig. 10

Relation between deflection of the deck and radial displacement of the pontoon

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Fig. 9

Model tank and related floating roof [13]




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