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Reinforced Concrete Beam (Eigen Frequency)

Posted May 13, 2019, 3:38 p.m. EDT 1 Reply

Vishnu Thamaraikannan
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Hello, I am new to comsol and i am working on reinforced concrete beam to analyse the displacement of the beam for 100Hz and 200 HZz frequency. The concrete beam is of 10*12 with steel reinforced. The beam is clamped on right and left side and the bounday load is given at the bottom(2000N/m2). The eigen frequency analysis shows diplacement in meters actually my displacement should be in microns. changing the boundary load seems no change in the displacement. Can anyone help me out with this.

1 Reply Last Post May 13, 2019, 4:50 p.m. EDT
Dave Greve
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Posted: 6 years ago May 13, 2019, 4:50 p.m. EDT

If you want the displacement for a known load at a given frequency you need to perform a frequency dependent analysis.

The value of the displacement in an eigenfrequency analysis is not meaningful. The eigenfrequency analysis gives the relative amplitudes and phases at different locations for a particular normal mode.

When you DO perform a frequency-dependent analysis, be aware that the displacement can become very large when excited exactly at a normal mode unless there is some damping in the system.

If you want the displacement for a known load at a given frequency you need to perform a frequency dependent analysis. The value of the displacement in an eigenfrequency analysis is not meaningful. The eigenfrequency analysis gives the relative amplitudes and phases at different locations for a particular normal mode. When you DO perform a frequency-dependent analysis, be aware that the displacement can become very large when excited exactly at a normal mode unless there is some damping in the system.

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