VKR Steel load-bearing.

[andreashe]

I have received a construction proposal that will support a concrete slab. Concrete cassettes will be supported by a UPE beam, which in turn has VKR 50x50x4 as columns underneath.

I think it seems a little thin, so my question is how much can a VKR 50x50x4 column that is 2200mm long support?

 

[justusandersson]

Approx. 90 kN.

 

[andreashe]

Approx. 90 kN.

Thank you. If I wanted to derive that load using a construction table, e.g., tibnors, how would you determine the value when it comes to columns?

 

[bossespecial]

There are tables at the back for column capacities in Tibnor's construction tables. Very easy to read, the input parameters are just column length and column dimension.

 

[Erik Lindroos]

There are tables at the back for column capacities in Tibnor's construction tables. Very easy to read, input parameters are just column length and column dimension

Do you know which load case they calculated (fixed restraint, pinned, etc.)? They state "Eurocode 3-1-1", but I can't find its definition.

When I use my old formula collection for VKR 50x50x4 and Euler's third buckling case (fixed restraint at one end, pinned at the other, buckling length 0.8*L), I get a slenderness ratio of 94. From the diagram, I then read a maximum allowable stress of about 100 N/mm2 (for SS2142 which should correspond to S355J2H as Tibnor states). With a cross-sectional area of 728 mm2, the maximum load is about 73 kN.

The slenderness ratio plays a very big role, and if I choose the slightly more generous (theoretical) buckling length of 0.7*L, the slenderness ratio is 82, maximum stress is about 125 N/mm2 and the maximum load is around 91 kN.

 

[Huddingebo]

One needs to calculate both the maximum vertical load for a given cross-section and for buckling where length and restraint/embedding play a role. A longer standing beam that is not braced along its length will withstand a significantly lower load before it buckles. So keep that in mind.

 

[witten]

A pillar like this is usually considered hinged at both ends.

I usually don't go under 70 mm steel pillars because they become very flimsy and weak for lateral accidental loads, even if it's possible to justify a smaller pillar.

 

[justusandersson]

Even the tables of wood guides for column loads are based on columns that are hinged at both ends (Euler's second buckling case).

 

[Erik Lindroos]

With Euler's second buckling case (column hinged at both ends), the slenderness ratio is approximately 117.5. According to the diagram (Karl Björk's Formulas and Tables), the maximum allowable stress is then under 65 N/mm², which gives a maximum load of about 45 kN for VKR 50x50x4.

I agree that it makes sense to start from Euler’s second buckling case (even if the third might be justified if the column is properly welded to the beam), but I would like to know what Tibnor's tables are based on since they end up at about 90 kN (Eurocode 3-1-1). It's important to know if the table is going to be used.

There is also a possibility that I am calculating incorrectly...

 

[bossespecial]

Since they most likely rely on completely different standards, the results you compare will always differ. Tibnor's tables are based on Eurocode, with hinged support conditions and this is the standard that applies. You don't have a sketch of the proposal?