If we assume that your vessel (tower) is anchored at the base, then the greatest motion will be at the top. Hence your conclusion as to the UBC formulae (greater loads as you go up).

Now if you attach piping to the top of the vessel, and run it down the side, with no other restraints, then you have essentially a whip. The motion at the bottom of the pipe will be larger than at the top, where it attaches to the vessel.

Is this realistic? Perhaps not. The reason is that you must have other restraints down the vessel, and along the pipe once it reaches the ground. These restraints will nullify the "whip" effect and you will move back to (the idea of) increasing loads as you move up.

Why might you obtain different results from those expected? This depends on how you modeled the restraints, specifically your guides down the vessel. If you applied double acting horizontal restraints, then they should be active in the dynamics solution. However, if you applied single directional horizontal restraints, or horizontal restraints with gaps, then they were linearized by the program for the dynamic solution. The linearization process either makes them linear (removes the gap), or it removes them completely. Check your <font color="0000ff">"Active BCs"</font> report (Active Boundary Conditions) to see how restraints were linearized. If this isn't what you want, then you may have to manually adjust the restraints before analyzing the system.


------------------
Regards,
Richard Ay (COADE, Inc.)



[This message has been edited by rich_ay (edited January 14, 2000).]