Hi
We are doing piping stress analysis on bridge. One side of the bridge is welded with fixed platform & other side of bridge have sliding support on well head platform.
Since well head & fixed platform are two independent structure we are considering maximum possible structural sway of two independent structure to calculate displacement of bridge piping normal OCC stress. ( maximum displacement in opposite direction of two platform).
For the case of seismic do we required to consider seismic displacement value ( supplied by structure) in opposite direction in reference to the platform ?
Or we can consider seismic displacement value in same direction in this case like wind case consideration.

Regards

Habib

I do not think you can assume that the two structures will deflect in phase.

You should not assume that the two platforms will move in phase under any conditions.

The safe design approach so far as relative movement is concerned is to assume thay will ALWAYS move exactly out of phase.