Torsion due to lateral load in the Steel beam Top flange 1

[Vivek19]

Hi,

I have a doubt in the Steel Piperack design. The pipes are resting over the Top flage of the beam & the Lateral Load is perpendicular to the steel beam. Since it is in the Top flange , It will create the torsion to that beam.

One of my Colleague says , To take care of this issue, we need to have special load combination with doubling the effect of the lateral force, ie guide load at critical condition and all other primary loads in the combination with appropriate safety factors.
And no need to apply the torsion at that location.


Doubling the lateral force alone will take care the Torsional effect?

Regards,
Vivek.

 

[msquared48]

Why don't you try to provide a slip mechanism in the direction of the longitudinal axis of the pipe at the wide flange to that the lateral force is not generated to begin with?

Mike McCann
MMC Engineering

 

[delagina]

torsion due to pipe friction and anchor loads are generally ignored. pipe weight will counter act it.

 

[delagina]

@mssquared, he cant do that. it's piping department scope. it will affect pipe stress design.

 

[dhengr]

Vivek19:

You need to get with your mechanical and/or piping people to get the actual loads, pipe support details, etc. They may not be applying significant lateral loads to most of the pipe rack beams and the pipe support system may not allow much rotation of your typical beams. But, then there may also be a few beams at changes in pipe direction and the like where they do expect you to resist significant loads other than just the weight of the pipe and its contents. This all has to be coordinated so you do the correct design. Maybe what your friend was telling you is some rule of thumb of his, ask him to explain. I can imagine that if you took the std. beam bending stresses from pipe weights and then some lateral loading (your guess) on the top flg. and applied this to only that flg., as a simple plate on edge, a simple beam; and then combined these two stress conditions at the top flg. tips, you would cover many/most stress conditions that you would expect to see. But, that’s not the way I would do it. I would want better defined load conditions form the piping guys, and I would want to know how the stiffness of their pipes and support systems might retrain my beams.

 

[delagina]

Piperack Design Guideline:

"Under normal loading conditions, torsional effects need not be considered since the pipe
supported by the beam limits deflection and rotation of the beam to the extent that
torsional stresses are minimal. However, torsion should be considered on an individual
basis when unusually large loads such as large anchor loads are applied to the beam
flange."

 

[UcfSE]

An old way of considering torsion in an I-shaped member is to consider it a lateral load on half of the beam only, with the force from the couple acting in the oppposite direction on the opposite half. Then it's like having a lateral load on a T shape instead of a twisting load on an I shape. Needless to say, this is an old way that many would no longer consider valid.

 

[ztengguy]

I think you need to get a structural engineer involved. There are liability and design issues here.