Existing Pallet Storage Racking Connected to Building Column

[Eng_Struct]

Hi Group,

I am evaluating an existing pallet storage racking that is to be modified (i.e., demolishing two rows at one end in the cross-aisle direction). The existing racking was originally constructed in the 1990s and is connected to an existing building column at one location. The connection to the column is detailed such that it will provide lateral restraint in one direction. I have determined the amount of load getting to the column in both existing and modified configurations. Based on the analysis, the modified configuration will result in about 25% less lateral load applied onto the column than the existing condition. Note that the lateral demand I am referring to is due to seismic and forces are calculated using NBC 2020 considering racking to be a free-standing structure (I appreciate that I mentioned racking being connected to the column but I believe calculating seismic demand based on free-standing assumptions is more realistic than treating it as an attachment because the connection between the two elements is not too robust and will only attract loads in relatively small magnitude).

The question to the group is would you typically check the column as well to confirm it can withstand combined axial (due to building dead and occupancy weights) and bending (due to the lateral load being applied from the racking)? Note that it is an interior column with a moment connection to the roof girder in the strong axis direction (i.e., bending around the strong axis). The lateral load from the racking will be applied in the weak axis direction (i.e., bending around the weak axis) roughly a foot below the bottom of the roof girder.

I was operating under the assumption that the column has been checked as part of the original design of the racking back in the 1990s, however, the owner does not have any information to confirm this. Checking the column for combined loading and possibly for the combined seismic demands is likely to result in a much bigger assignment/exercise. Can I get away with checking the existing column/building behavior given the fact that the modified arrangement of the racking is going to apply lessor forces than it will experience in the current condition? I am just concerned about opening myself to risk here just because I have touched the racking and now I feel like I own everything in the design including the connection to the existing column and its impact on the building.

Some guidance will be much appreciated.

 

[skeletron]

My Short Answer:
Yeah. I would do a check on the existing column just to satisfy that everything is A-OK.
Why?
Reason #1: Your gut instinct is questioning a central assumption in your design.
Reason #2: There is no existing information and your assumption is based on this information existing AND passing a check.
Reason #3: 1990s seismic design and racking. Both have experienced a lot of changes in recent years.
Reason #4: Is there a geotech report that confirms the shear wave velocity or site class?

What is the connection for the racking to column? Is it necessary? Is it possible to have a slip connection that can allow for the free-standing deflection and therefore not impart the load on the column?

I empathize with the conflict in your situation. Do you check a janky existing structure if you are not directly attaching to it (but you kind of are in this case)? Can you just check the thing your billings are covering and ignore the rest assuming that it was changed for the original loading? Let yourself sleep at night and do a check.