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PIPE RACK – Wind Study Software: CivilFEM powered by Marc

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Case study description

CASE STUDY DESCRIPTION

The goal of this analysis is to determine if the wind generates vibration in a pipe rack. To achieve the goal two analysis types will be performed:

STRUCTURAL - MODAL ANALYSIS

• To determine the frequencies of the normal modes a modal analysis has been performed considering the mass and stiffness of the beam structure of the rack + trays + AirCoolers + pipes

CFD ANALYSIS

• To determine the frequency of vortex sheeding due to wind at the pipes different CFD analyses have been performed.

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Masses and components

The rack as well as the pipes have been modeled with beam elements of different sections Sections of the rack

HE 180A HE 200A HE 220A HE 240A HE 280A HE 300A HE 340A HE 400A HE 450A HE 500A HE 550A HE 600A HE 650A HE 500B HE 700M

Different pipe sections have been used: D from 10” to 48”

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Masses and components

Tray masses have been modeled using forces AirCooler masses have been modeled using forces

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Modal analysis

Z Direction – Critical mode: Freq=0.9Hz aprox. Mass fraction 45%

In the modal analysis Tray and AirCooler masses have been considered using the CivilFEM tool ‘convert forces to masses’

X Direction – Critical mode: Freq=0.7Hz aprox. Mass fraction 65%

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Conclusions

The frequencies of the critical normal mode in X Direction and the frequencies of the vortex shedding are far enough to avoid resonance phenomena. Therefore the movements of the pipe rack due to wind loads are small enough to certify the structure stability.