Moment of Inertia for S Type I Beam
 

I have an I beam that is S type with tapering legs that is A36 steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind of
load. Can anyone help me out? Thanks, Steve

Moment of Inertia for S Type I Beam
 

Naw! That was elongation, not deflection. Looked right to me.

BS
"eberlein" wrote in message
...
3.42E5 inches? A deflection of 5.4 miles on a 38" long beam? I think you
need to check your calculations again.

Steve wrote:

I have an I beam that is S type with tapering legs that is A36 steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind of
load. Can anyone help me out? Thanks, Steve

Moment of Inertia for S Type I Beam
 

Assuming S6x17.25
L = 3'
P = 40,000 lbs
I get .051" deflection
shear value is OK
can't check web crippling because you don't give length of end bearing.

"Steve" wrote in message
om...
I have an I beam that is S type with tapering legs that is A36 steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind of
load. Can anyone help me out? Thanks, Steve

Moment of Inertia for S Type I Beam
 

Roy Jenson wrote in message ...
You need to calculate the max stress before you worry about
deflection. My calculations show it will bend like a pretzel
since you will be at about 43.6kpsi at your 20k ton load.

Cheers.

I am curious how this beam will "bend like a pretzel"? How will it
bend like a pretzel if the deflection at load is only .05"? I
understand what the yield of mild steel is and that it is mostly
regarded to be 36,000 psi. However most mild steels are now rated at
around 47,900 psi from what I have been reading in various resources
and journals. Is this incorrect? This Beam is going to be used for the
top of a hydraulic press and will be supported by 2- 2.5"x2.5" .25
wall square tubing. I can always make it less wide to make the beam
more rigid and could also use a 10 ton jack instead. I crunched the
numbers on these and they came in quite a bit under the yield point.
Any more help is greatly appreciated. Thanks, Steve

Moment of Inertia for S Type I Beam
 

Roy Jenson wrote in message ...
You need to calculate the max stress before you worry about
deflection. My calculations show it will bend like a pretzel
since you will be at about 43.6kpsi at your 20k ton load.

Cheers.

Steve wrote:

I have an I beam that is S type with tapering legs that is A36 steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind of
load. Can anyone help me out?



I am curious how this beam will "bend like a pretzel"? How
will it
bend like a pretzel if the deflection at load is only .05"? I
understand what the yield of mild steel is and that it is mostly
regarded to be 36,000 psi. However most mild steels are now rated at
around 47,900 psi from what I have been reading in various resources
and journals. Is this incorrect? This Beam is going to be used for the
top of a hydraulic press and will be supported by 2- 2.5"x2.5" .25
wall square tubing. I can always make it less wide to make the beam
more rigid and could also use a 10 ton jack instead. I crunched the
numbers on these and they came in quite a bit under the yield point.
Any more help is greatly appreciated. Thanks, Steve

Moment of Inertia for S Type I Beam
 

In a short beam like that, deflection is not usually a consideration. I
used the formula stress= (weight x length)/(4 x Z), and came up with
43,000 psi, definitely too high.

stress = (40,000 pounds x 38 in)/ (4 x 8.77 cu in)

Z =I / distance to extreme point, (around 3 inches)

Another consideration is how well spread out the pressure is. If the
support is really a point, the beam could kind of fold up. If the load
is spread out over several inches of beam, that is not likely to occur.

You need a heavier beam to get the stress to 12,000 psi or less. In an
S-beam, a 12 inch beam would be close, rather than a 6 inch beam.

Richard



Steve wrote:

I have an I beam that is S type with tapering legs that is A36 steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind of
load. Can anyone help me out? Thanks, Steve

Moment of Inertia for S Type I Beam
 

Well, the allowable fiber bending stress for A-36 has been 24,000psi in
building frames for the last 35 yrs, as far as I know. That assumes adequate
lateral support of the compression flange, which is questionable in an
H-frame hydraulic press.
Allowable stresses and safety factors for machine designers may be
different.
Enough time has been spent on Steve's press. He'll have to eyeball the
design.


"Richard Ferguson" wrote in message
...
No way would I design to 24,000 psi, not nearly enough safety factor,
given a yield point for structural steel in the range of 33,000 to
36,000 psi. 12,000 psi has a reasonable engineering safety factor built
in.

Richard


larsen-tools wrote:

You need a beam with a section modulus (S) = 15 in^3 (f sub b of
24000psi, working stress for A-36 steel)

"Richard Ferguson" wrote in message
...
In a short beam like that, deflection is not usually a consideration.
I
used the formula stress= (weight x length)/(4 x Z), and came up with
43,000 psi, definitely too high.

stress = (40,000 pounds x 38 in)/ (4 x 8.77 cu in)

Z =I / distance to extreme point, (around 3 inches)

Another consideration is how well spread out the pressure is. If the
support is really a point, the beam could kind of fold up. If the
load
is spread out over several inches of beam, that is not likely to
occur.

You need a heavier beam to get the stress to 12,000 psi or less. In
an
S-beam, a 12 inch beam would be close, rather than a 6 inch beam.

Richard



Steve wrote:

I have an I beam that is S type with tapering legs that is A36
steel.
The width is 3.5" and the height is 6". The web is .5" thick and the
ends of the legs start out at .25" thick and taper to .5" thick at
the
web. I need the Moment of Inertia for this beam. I figured it using
Machinery's Handbook at I=26.49. I just want to make sure this is
correct. I also figured that with both ends of this beam simply
supported with a beam length of 38" and a single load point exactly
in
the middle of the beam of 20 tons the Deflection at Load would be
3.42x10 to the fifth inches. That sounds a little low for that kind
of
load. Can anyone help me out? Thanks, Steve