Design of Column with very large eccentricty

[StewardMM]

I am trying to design a column whose moment is very large and small axial force, eccentricty of which is roughly about 8m.

I have read that it should be design as beam in tension. I have designed it that way, and is wondering how the bars would be arranged. Should the resulting number of bars be distributed in the whole beam section?

 

[fcu45]

It happened that I had similar case
I designed it as column and didn't have problem in bars distribution.

Good luck

 

[yakpol]

Place more reinforcing in the tensile zone... If you trust the contractor...

 

[hokie66]

Sounds like a beam to me. Regardless of the orientation, if the member is predominately flexurally loaded, design it as a beam.

 

[frv]

hokie is right.. the distinction of beam or column in not one of orientation.. it is determined by the primary function of the member.

 

[fcu45]

If it is mainly subjected to wind load, you may not be able to decide the location of tension as wind direction usually alternates.

 

[rowingengineer]

Agree on beam design and reo should be in thet tnesion zone. IF this zone changes the reo should be present in each tension zone.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[grantstructure]

Your question is a bit alarming. Why have you designed the member as a "beam in tension" if it has slight net compression?

Also, your design should dictate exactly to you where your steel goes. I.E. you have to have assumed a c.g. of steel in order to have performed your design. Why would you then consider distributing that steel in some other pattern? Your steel arrangement has to satisfy the center of gravity of steel you used in your calculations.

You may decide to place some additional vertical steel to handle cracking and so on. The end result will look something like a column, with your main beam steel on the tensile side, some additional bars on the compression side to keep creep from being excessive, or as compression steel, and additional bars along the face as you find necessary to handle cracking (think mid-steel in deep flexural members, if your member is indeed deep enough.) Remember also that you will likely have to splice the bars somehow at the base, and that the splice will effect the depth of c.g. you are assuming for your bending steel, at the critical section. Magnify your moments if the column can sway, or run a p-delta analysis.

Yakpol's point is that if you do not make the reinforcing symmetrical--e.g. place enough reinforcing on each face such that you could handle the design bending load in any direction--then it will be critical that the contractor understand the asymmetrical nature of the column reinforcing, and place it in the correct orientation--this will be true for any dowels as well.