Web Crippling 2

[EIT2]

Will somebody please check my math?

AISC/ASD 9th Edition, Equation (K1-5)

I have a W8x24, Fy=50 ksi, bearing 6" on a solid grouted, concrete masonry bond beam. I have approximately 4K of solid grouted concrete masonry bearing on top of the bearing end of the beam. The allowable compressive force that I am calculating (1219 lb) seems so low, I am convinced I am misunderstanding something.

Any comments?

Thank you!

 

[PEinc]

Did you check out AISC, 9th Ed., page 2-31? Use the max. end reaction condition equations.

 

[PEinc]

Also, make sure your equation values are in the proper units.

 

[EIT2]

Thank you for your responses!

Yes! AISC, 9th, page 2-31 is where I started. My max end reaction is 66K. But then the web crippling formula fails my design intent. Both of the two conditions need to be considered.

I've checked my units. Have either of you run the formula?

Please give it a try and let me know what you come up with.

Thank you!

 

[JAE]

Variables:
N = 6 in.
d = 7.93 in.
tw = .245 in.
tf = .4 in.
Fyw = 50 ksi

Eq K1-5 -
R = 38.5 kips

 

[PEinc]

I ran both formulas for a W8x24 beam, 6 inch bearing length, end reaction condition. I got an allowable load for web yielding of 66 kips and an allowable load for web crippling of 39 kips.
N = 6.0 inches bearing length
d = 7.93 inches beam depth
k = 0.875 inches
tw = 0.245 inches web thickness
tf = 0.400 inches flange thickness
Fy = 50 ksi

 

[EIT2]

Someone please check my math!
What am I doing wrong?

(34*(0.245)^2)*(1+3*(6/7.93)*(0.245/0.4)^1.5)*(SQRT(50000*0.4/0.245))=1217 lb

Thank you!

 

[mjohan]

EIT2,
Maybe you have caught the error but if not, the Fyw of steel must be in ksi since the formula is the max end reaction in (kips)

 

[EIT2]

I did'nt catch the error until you pointed it out!
My trial is over!

Thank you!

 

[jheidt2543]

EIT2,

You bring up a good point to remember, that is, when your gut gives you that "funky feeling" that something isn't right - it usually isn't. Listen to your gut feelings!

We all make mistakes, the key is to find them before they cause a problem. Many times you get a feeling that something is wrong, but you can't quite put your finger on it. Listen to that feeling and look at the problem from a different angle.

 

[civeng]

Hi everyone,

I agree with jheidt2543, thats what these forums are for. When in doubt looking at it with other people helps.

Have a good one guys and gals