Steel Design - Effective lengths of columns - SD424

This video overviews how to determine the effective length of columns, and how a single column can have multiple effective lengths.
Copyright Stellenbosch University

[@hasey2177]

I really appreciate the way you explain it. I think you have more experience.

[@nicolasjativa1441]

So well explained!!!

[@me09hha]

Great explanation

[@sourabhshrivastav3964]

Great Explanation

[@sothattheng8624]

Thanks for sharing!

[@mohanadhabh772]

man you are great >>>>> thanks

[@zian.2493]

Can you please make a video on how to counter this buckling effects ..like providing stiffeners what type of stiffeners.

[@mahmodmohamadmahfoud658]

I believe that For the Ly, lateral supports only prevent outer flange from moving in & out. so, in order to consider Ly = the girt spacing; flange brace is mandatory to constrain the inner flange movement as well

[@firesun]

This is a good point. To get an accurate value of KLy with multiple side connections a finite element analysis or testing may be required. However, in most cases connections in real structures are much stiffer than pins (e.g. a T-cleat with 4 bolts into a girt and lots of sheeting on a face). Also, the web adds stiffness and links the flanges together. But yes - if you had a pure pinned connection at the lateral restraint, and a thin web or very deep section it may be under-conservative to consider a restraint from a single flange. However, the torsional resistance will also capture this behaviour to some extent. For compressive buckling the entire section has to move sideways, and only one flange can moved. More detailed analyses would needed to highly loaded or complex structures where such behaviour is important.

[@mahmodmohamadmahfoud658]

@@firesun Impressive 👏 Thank you, appreciate it.

[@mtbmcc2493]

Agree

[@mirzanaushadbaig9147]

@@firesun Ly in case of I beams is different for both flanges. But for tubular sections Ly can be as you have explained in the lecture as the flanges of tubular sections are firmly connected with two webs.

[@zian.2493]

2:14 can you correct/ verify clearly where direction it buckles?

[@Alias102.]

Would the effective length factor K change if the column were to be restrained say twice or once along its length.

[@structuralchannel2507]

Sr can you send a way to contact you?

[@tominmathew344]

Sir, can we cut off the Ly as the distance between the channel section if it’s a moment frame.

[@richard_walls]

Normally the length is taken as the distance from centre to centre of supports.

[@structuralchannel2507]

Hii sr what will be effective length of free standing column with one end fixed other free

[@firesun]

K=2.0 for a cantilever normally

[@Kiwistoicist]

Did you get ly and lx in the wrong way？ the weak axis is Ly which lateral supports only at top and bottom

[@firesun]

The girts provide lateral support about the weak axis so Ly is shorter.

[@ranjanty]

Hi, could you please help me? I have a 48inx24in stainless steel table with tubular legs that are 32.75inches high. I want to increase the weight capacity which is 500 something lbs. If I fill the legs with concrete and a piece of rebar would that increase the weight capacity of the table? Maybe to 800 lbs. I'm 70 and I'm no longer able to figure it out. Thanks to anyone who chooses to help ❤

[@firesun]

Sorry, my brain does not work as well in lbs and inches. Strength is often governed by member capacity and also connections. Hence, if you strengthen something you also need to ensure that the connections between members are sufficient. As a rough rule of thumb if you take the area of concrete at around 40% of the strength, say 20 MPa for a low quality concrete, and add on strength of the rebar at 60% of its yield strength you have a ballpark estimate of the capacity. 800lbs is not that much load for a steel and concrete structure, especially if there are 4 legs.

[@ahmedyaqub2377]

How can I prevent cracks in partition walls due to deflected steel structural beams' interaction?

[@firesun]

Stop the beam from deflecting (i.e. stiffen it) or isolate the members from each other.

[@ahmedyaqub2377]

@@firesun Regarding isolating the members from each other is there any code mentioned that, like IBC or AICS Standard, Please help me

[@firesun]

@@ahmedyaqub2377 - You simply need to install a soft material that can accommodate the movement, and keep the wall and beams not connected to each other.

[@ahmedyaqub2377]

@@firesun Dea Sir, there is a controversy in our company that insulation is not required and it is possible to make the non-loading partitions directly contacted with steel truss without separation, so I need a paragraph in the code that stipulates that the isolation must be achieved

[@firesun]

@@ahmedyaqub2377 You will not normally find this in a code. However, if a steel struss moves more than a wall can allow then the wall will crack. It is based on physics rather than codes.

[@sensennsen]

"nothing is fixed in real life, with both the tolerances and the rest of it..." witty