Silly question: PLF to PSF

[gmoney731]

Hello,

This is an embarrassing and silly question for a structural engineer to ask.

Let's say I have an L2x2x1/4, with a weight of 3.19 PLF (from AISC) and an area of 0.944 in^2 (0.0065 ft^2). It is 5' long.

I want to calculate a PSF load associated with that angle...how would I go about getting that answer.

I understand that AISC takes 490 PCF x A_angle = 3.19 PLF, and that times 5' can give me ~16 LBS as the weight...but what is the PSF equivalent of this?

Thanks for your time.

 

[jayrod12]

You would take that PLF load and divide it by the spacing of the angles.

 

[DaveAtkins]

jayrod12 is correct. If you are having trouble visualizing this, imagine taking the 3.19 pounds for a one foot length of angle, and "smearing" it half the angle spacing in each direction.

DaveAtkins

 

[gmoney731]

You would take that PLF load and divide it by the spacing of the angles.

Can you explain this more? I was going to take the 3.19 PLF, multiply it by the length of the angle to get a LBS value, multiply that by the number of angles, and then divide that by the tributary area (plan view) of the joist?

 

[gmoney731]

Can you explain this more? I was going to take the 3.19 PLF, multiply it by the length of the angle to get a LBS value, multiply that by the number of angles, and then divide that by the tributary area (plan view) of the joist?

 

[jayrod12]

That is the same calculation, just more steps.

Let's say you have 5 ft long angles at 3.2 PLF and you have them spaced at 4ft on-centre. You could go 3.2PLF*5ft*2=32 lbs and divide that by the total area = 2*5ft*4ft=40 square feet equaling 0.8 PSF (assuming we just look at two angles, scale up for as many as you have). Or take 3.2PLF divided by 4ft = 0.8 PSF. The same number with less steps and less chance for error. And can be applied universally regardless of length and width of area.

 

[BAretired]

It is indeed a silly question. PLF cannot be converted to PSF no matter how hard you try. They are simply different units.

BA