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Modes of Vibration of above ground fixed-roof steel tanks

Juan C. Virella Crespo, G.S.Dr. Luis A. Godoy, Chairman

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MODES OF VIBRATIONS OF FIXED-ROOF TANKS

DESCRIPTION OF STEEL TANKS MODELSModes of vibration of above ground storage steel tanks with fixed roofs, are obtained computationally with ABAQUS finite element program. Three different types of tank roof configuration are considered: dome-roof, cone-roof, plane-roof.The steel tank is considered empty, and self-supported roof.Three different diameter to height (D/H) ratios are considered for each tank roof configuration: D/H = 0.24, D/H =0.42, D/H = 0.63.

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STEEL TANK MODELS

Cone-roof tankD/H = 0.63

roof slope = 3V:16H

Cone-roof tankD/H = 0.63

roof slope = 0.75V:12H

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STEEL TANK MODELS

Dome-roof tankD/H = 0.63

Roof arc radius = 42.062 m

Plane-roof tankD/H = 0.63

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Cone-roof tank model

Cone-roof modelD/H = 0.63

Roof slope 3V:16H

Mode 1T1 = 0.377 sec.ω1 = 2.651 Hz

Mode 9T9 = 0.338 sec.ω9 = 2.958 Hz

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Cone-roof tank model

Cone-roof modelD/H = 0.63

Roof slope 0.75V:12H

Mode 1T1 = 0.666 sec.ω1 = 1.501 Hz

Mode 2T2 = 0.665 sec.ω2 = 1.504 Hz

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Dome-roof tank model

Dome-roof modelD/H = 0.63

Roof arc radius = 42.062 m

Mode 1T1 = 0.338 sec.ω1 = 2.958 Hz

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Plane-roof tank model

Plane-roof modelD/H = 0.63

Mode 1T1 = 7.873 sec.ω1 = 0.127 Hz

Mode 2T2 = 3.773 sec.ω2 = 0.265 Hz

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Natural Frequencies and PeriodsDescription of Model:

Model of tank:Dome-Roof TankD/H = 0.63D = 30.48 mH = 19.337 m

Mode Freq [cycles/sec] T [s]1 2.9578 0.3382 2.9578 0.3383 2.9622 0.3384 2.9625 0.3385 3.0455 0.3286 3.0456 0.3287 3.0458 0.3288 3.0459 0.3289 3.195 0.313

10 3.1952 0.31311 3.2389 0.30912 3.239 0.30913 3.3985 0.29414 3.3985 0.29415 3.5512 0.28216 3.5521 0.28217 3.6464 0.27418 3.6466 0.27419 3.9317 0.25420 3.9318 0.254

Description of Model:

Model of tank:Cone Roof TankD/H = 0.63D = 30.48 mH = 19.337 m

Mode Freq [cycles/sec] T [s]1 2.6511 0.3772 2.6514 0.3773 2.6751 0.3744 2.6752 0.3745 2.7964 0.3586 2.7966 0.3587 2.8008 0.3578 2.8009 0.3579 2.9575 0.338

10 2.9575 0.33811 2.9614 0.33812 2.9617 0.33813 2.9994 0.33314 2.9996 0.33315 3.0448 0.32816 3.0448 0.32817 3.0461 0.32818 3.0463 0.32819 3.1939 0.31320 3.1939 0.313

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Natural Frequencies and PeriodsDescription of Model:

Model of tank:Plane-Roof TankD/H = 0.63D = 30.48 mH = 19.337 m

Mode Freq [cycles/sec] T [s]1 0.12702 7.8732 0.26506 3.7733 0.26506 3.7734 0.43592 2.2945 0.43593 2.2946 0.49759 2.0107 0.63922 1.5648 0.63923 1.5649 0.76272 1.311

10 0.76273 1.31111 0.87445 1.14412 0.87448 1.14413 1.0628 0.94114 1.0628 0.94115 1.1205 0.89216 1.1412 0.87617 1.1412 0.87618 1.3977 0.71519 1.3978 0.71520 1.4391 0.695

Description of Model:

Model of tank:Cone-Roof TankRoof slope 0.75V:12HD/H = 0.63D = 30.48 mH = 19.337 m

Mode Freq [cycles/sec] T [s]1 1.501 0.6662 1.5036 0.6653 1.5037 0.6654 1.5595 0.6415 1.5595 0.6416 1.5958 0.6277 1.5959 0.6278 1.7765 0.5639 1.7766 0.563

10 1.9811 0.50511 1.9813 0.50512 2.0232 0.49413 2.0233 0.49414 2.0898 0.47915 2.0899 0.47916 2.3241 0.43017 2.3242 0.43018 2.6716 0.37419 2.6717 0.37420 2.9571 0.338