We're tying two towers together with a section of mostly unsupported pipe (the towers are close together).

In normal analysis when one considers wind in his analysis, it's applied as a static load, and the entire system blows in one direction to its individual calculated displacements, and when the wind goes away, everything returns nicely to its initial state.

Normally this is a decent design point.

However, in the real world, when the wind blows and gusts, everything ends up swaying at its natural frequency. Back and forth, back and forth.

When you have a pipe connecting two different pieces of equipment / structures that are swaying at different natural frequencies, then if you were to take a static snapshot in time, it would look like wind blew one vessel (or structure) in the completely opposite direction from the other.

The analogue would be to perform a time-history seismic analysis with multiple structures to achieve this response. In this case, we could do this statically and assume the worst case opposite deflection.

Questions to the panel:
• Have you performed analysis on a similar piping configuration?
• Have you considered these dynamic effects before?
• Is the proposed methodology sound, or is it over-conservative?

Thanks.