Cutting and Replacing Steel Column

[asixth]

Hi guys,

I need to post another question. I have an existing structure with a higher and lower roof. Currently both roofs are supported by a steel column which is shown in my first sketch. Because of an occupational change of the building I now need to move the column by approximatley 5' (1500mm). My thoughts where to cut the column below the lower roof, and install a new column in the location 5' away from the existing location, as shown on the second sketch. I believe the best solution is to prop the lower roof and cut the lower roof rafter so a new column can be installed that supports both upper and lower rafters, however I do not believe this will be feasible because of the excessive propping and cutting that will be required. With the second option (page 2), they can install the new column and then remove the existing column without any propping of the existing structure.

What are others opinions on this approach and what do you think the best option would be?

 

[ishvaaag]

Analysis permitting, and if you see no inconvenience in adopt the solution preferred by users or builder, why not?

But the key point is that you need be sure what they are proposing is entirely and properly safe at any stage.

 

[swearingen]

Please pay close attention to your load path. It changes with each of the three sketches.


If you "heard" it on the internet, it's guilty until proven innocent. - DCS

http://www.eng-tips.com/supportus.cfm

 

[csd72]

asixth,

I would do similar to the third sketch except provide some diagonals to form a truss between the rafters.

What restrains the old column from buckling into the page just above the cut?

 

[hokie66]

asixth,

The second option is certainly the simpler. As long as the rafter over the new column works, that is the way I would do it. You may have to add some fly bracing.

 

[BSE05]

When I look at your proposed sketches, I see alot of hinges.
The approach I am familiar with is adding a new horizontal beam under the cut column connecting between an old column and the new.

Your approach may work, but I would be suprised if the existing horizontal members would be strong enough?

Let us know what you decide.

 

[asixth]

csd72

There will be purlins at both roof levels that run into the page (hypothetically). The column that we are cutting will essential become a tension member primarily because the rafter for the upper roof is much stiffer than the lower roof (460UB compared to 250UB...W18 compared to W10).

 

[KootK]

I attached a sketch showing another possible solution. I think that the detail, as well as my concerns for it, are similar to csd72's suggestions.

 

[csd72]

KootenayKid,

Yes thats the sort of thing I was talking about, but you would need to check that there is a roof membrane at both top and bottom beams to take the push/pull effect.

Only way to avoid the push/pull is to continue the truss back to the next column.