support sat on both side of a expansion joint 1

[struengineer]

I need to design a steel dunnage support for a HVAC unit. Four supporting posts will be sat on four existing building columns which located at both sides of an expansion joint. (2 columns on one side of the joint and the other 2 columns on the other side of the joint).

I am afraid of either horizontal movement due to temperature at the base of the Dunnage support or vertical movement due to different settlement on both sides of expansion joint will cause a problem of my dunnage support.

Is anybody here who solved this problem before? What kind of details I should use to handle this problem? Please help

 

[cntw1953]

The word wasn't exactly correct.

If your unit is on top of the roof, and located in between four existing column below, for duct work, you can simply provide a new 4 posts frame with beams and hanger type support.

For equipment, you can provide beams in two layers (elevations), and let the unit sits in.

For either case, your unit will be above the roof, away from the expansion joint. The beam connections can be designed to accomodate the lateral movement, and the posts (as short as possible) shall be designed for the lateral load effects. If there is not much problem in fastening the posts to the roof, you may even consider adding thick rubber pads below the base plates (can be sandwiched) to absorb some vertical displacement and energy due to dynamic loads.

Sorry for confusion caused by my poor choice of word. Hope I didn't miss the point this time.

 

[rowingengineer]

struengineer,
following on from what hokie is suggesting, is if you know a fair bit about the building it shouldn't be too hard to come up with a better guess on horizontal movement. It is a relatively easy calculation if you stay on the conservative side to estimate the expansiona nd contraction of the joint over the temputer change.

as for the vertical settlement, again i'm with hokie.

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