Subject: [Shop-talk] weight capacity of aluminum channel

From: "john niolon" <[email-masked]>
Date: Thu, 1 Jul 2021 21:56:24 -0500

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I'm thinking about using aluminum channel for a set of ramps for my ca=
r hauler.  I have some 'available' that is  10" wide with .50 web thic=
kness and almost 3" flange... about 15# per ft.

ramps will be 7-8'=20
long =E2=80=A6..  and will go from ground to 17" high trailer deck... =
 truck weight is 5300 +/- =E2=80=A6 with front end weighting 3840.   I=
 can't find a table telling me weight capacity of
channel with the load traveling up the wide web...   like this   any i=
deas on capacity ??

thanks
john

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<DIV>I'm thinking about using aluminum channel for a set of ramps for =
my car hauler.&nbsp; I have some 'available' that is&nbsp; 10" wide wi=
th .50 web thickness and almost 3" flange... about 15# per ft.</DIV>
<DIV>&nbsp;</DIV>
<DIV>ramps will be 7-8' long =E2=80=A6..&nbsp; and will go from ground=
 to 17" high trailer deck...&nbsp; truck weight is 5300 +/- =E2=80=A6 =
with front end weighting 3840.&nbsp;&nbsp; I can't find a table tellin=
g me weight capacity of</DIV>
<DIV>channel with the load traveling up the wide web...&nbsp;&nbsp; li=
ke this&nbsp;&nbsp; any ideas on capacity ??</DIV>
<DIV>&nbsp;</DIV>
<DIV><IMG alt=3DImage87ABA31D src=3D"cid:1UZ2jB6kD5.3Za19vpLCjR@johns-=
desktop"></DIV>
<DIV>&nbsp;</DIV>
<DIV>thanks</DIV>
<DIV>john</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV></BODY></HTML>

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_______________________________________________

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Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive

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From: Donald H Locker <[email-masked]>
Date: Fri, 2 Jul 2021 06:16:19 -0400

BIG NOTE: please check my calculations and assumptions; I haven't
actually done any of this for nearly 40 years.

TLDR: They might not work.

The significant supporting bits are the two flanges (3in x 0.5in); the
plate across the top adds very little strength.

All calculations below in pounds and inches.

The maximum stress on the webs (if the weight is perfectly divided
between them; more on that later) will be (equation 1-1 in reference 1)
with the weight at the center of the ramp. Fb (bending stress in the
flange of the channel) must be less than the yield stress of the channel
material.

  Fb = M*c/I

[Ref 2] M for each web: PL/8 = P*120in/8 = P*15in [P is point load, lb]
[email] c for each web: 1.5in
[Ref 4] I for each web: (b*(h^3))/12 = ((0.5in)*(3in)^3)/12 = 1.125in^4

  Fb = (P*15in*1.5in)/1.125in^4 = P*20 lb/in^2

For the given situation, p=3840lb, so Fb (max) is 3840*20 = 76800lb/in^2
distributed between the two channels, each with two flanges. Since Fb
must be less than the material yield stress, 10000 psi for some kind of
structural Al, but not high-strength material [Ref 3], this doesn't look
very good. Each flange would be loaded to about 19200lb/in^2 if all
loads were perfectly distributed. (Note that high-strength Al (e.g.
6061) can have a yield stress of 45000lb/in^2 so looks much more likely
to succeed, but I don't know how much I'd trust that.)

My biggest concerns would be the division of stresses between flanges
(if one channel tilts a little or is not sitting perfectly flat on the
trailer or ground, stress sharing will be uneven and one flange make
take all stress) and the potential for flange instability (see notes in
1.3.1.5 in Ref 1.) This may not be a problem because the flanges are not
particularly deep, but I watched a boat hung from I-beams drop when a
structural I-beam twisted slightly from imperfect loading and the entire
structure quickly twisted into a totally unsupportive mess.

References:
1 Beam stress/strain:
<https://engineeringlibrary.org/reference/simple-beam-bending-air-force-stress-manual>

2 Beam force/reaction:
<https://engineeringlibrary.org/reference/beam-forces-moments-air-force-stress-manual>

3 Material properties:
<https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html>

4 Area moments:
<https://www.engineeringtoolbox.com/area-moment-inertia-d_1328.html>

ATB,
Donald.
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On 2021-07-01 10:56 p.m., john niolon wrote:
> I'm thinking about using aluminum channel for a set of ramps for my car
> hauler.  I have some 'available' that is  10" wide with .50 web
> thickness and almost 3" flange... about 15# per ft.
>  
> ramps will be 7-8' long …..  and will go from ground to 17" high trailer
> deck...  truck weight is 5300 +/- … with front end weighting 3840.   I
> channel with the load traveling up the wide web...   like this   any
> ideas on capacity ??
>  
> Image87ABA31D
>  
> thanks
> john
>  
>  
> 
> Donate: http://www.team.net/donate.html
> Suggested annual donation  $12.96
> Unsubscribe/Manage: http://autox.team.net/mailman/options/shop-talk/[email-masked]
> 

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---

From: Donald H Locker <[email-masked]>
Date: Fri, 2 Jul 2021 06:29:07 -0400

First oops - I used 10ft length, not 8ft. At 8ft, the numbers look
better by about 20%

Donald.

[email-masked]

utox.team.net

---

From: Jeff Scarbrough <[email-masked]>
Date: Fri, 2 Jul 2021 08:42:16 -0400

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I haven't done it on 35 years, but at least your equations look familiar.
I find that comforting.

If the capability is questionable, would solid wood blocks of a suitable
height to support the channel somewhere near the center help?

On Fri, Jul 2, 2021, 06:34 Donald H Locker <[email-masked]> wrote:

> > flange of the channel) must be less than the yield stress of the channe=
l
> > material.
> >
> >   Fb =3D M*c/I
> >
> > [Ref 2] M for each web: PL/8 =3D P*120in/8 =3D P*15in [P is point load,=
 lb]
> > [Ref 4] I for each web: (b*(h^3))/12 =3D ((0.5in)*(3in)^3)/12 =3D 1.125=
in^4
> >
> >   Fb =3D (P*15in*1.5in)/1.125in^4 =3D P*20 lb/in^2
> >
> > For the given situation, p=3D3840lb, so Fb (max) is 3840*20 =3D 76800lb=
/in^2
> > structural Al, but not high-strength material [Ref 3], this doesn't loo=
k
> > 1.3.1.5 in Ref 1.) This may not be a problem because the flanges are no=
t
> > structural I-beam twisted slightly from imperfect loading and the entir=
e
> > <
> https://engineeringlibrary.org/reference/simple-beam-bending-air-force-st=
ress-manual
> >
> >
> > 2 Beam force/reaction:
> > <
> https://engineeringlibrary.org/reference/beam-forces-moments-air-force-st=
ress-manual
> >
> >
> > 3 Material properties:
> > <https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.htm=
l
> > <https://www.engineeringtoolbox.com/area-moment-inertia-d_1328.html>
r
> >> ramps will be 7-8' long =E2=80=A6..  and will go from ground to 17" hi=
gh trailer
> >> deck...  truck weight is 5300 +/- =E2=80=A6 with front end weighting 3=
840.   I
> >> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/shop-talk/[email-masked]
> >>
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<div dir=3D"auto">I haven&#39;t done it on 35 years, but at least your equa=
tions look familiar.=C2=A0 I find that comforting.<div dir=3D"auto"><br></d=
iv><div dir=3D"auto">If the capability is questionable, would solid wood bl=
ocks of a suitable height to support the channel somewhere near the center =
help?</div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"g=
mail_attr">On Fri, Jul 2, 2021, 06:34 Donald H Locker &lt;<a href=3D"mailto=
:[email-masked]">[email-masked]</a>&gt; wrote:<br></div><blockq=
uote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc =
solid;padding-left:1ex">First oops - I used 10ft length, not 8ft. At 8ft, t=
he numbers look<br>
better by about 20%<br>
<br>
Donald.<br>
--<br>
*Plain Text* email -- it&#39;s an accessibility issue<br>
() no proprietary attachments; no html mail<br>
/\ &lt;<a href=3D"https://www.georgedillon.com/web/html_email_is_evil.shtml=
" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.georgedillon.=
com/web/html_email_is_evil.shtml</a>&gt;<br>
<br>
On 2021-07-02 6:16 a.m., Donald H Locker wrote:<br>
&gt; BIG NOTE: please check my calculations and assumptions; I haven&#39;t<=
br>
&gt; actually done any of this for nearly 40 years.<br>
&gt; <br>
&gt; TLDR: They might not work.<br>
&gt; <br>
&gt; The significant supporting bits are the two flanges (3in x 0.5in); the=
<br>
&gt; plate across the top adds very little strength.<br>
&gt; <br>
&gt; All calculations below in pounds and inches.<br>
&gt; <br>
&gt; The maximum stress on the webs (if the weight is perfectly divided<br>
&gt; between them; more on that later) will be (equation 1-1 in reference 1=
)<br>
&gt; with the weight at the center of the ramp. Fb (bending stress in the<b=
r>
&gt; flange of the channel) must be less than the yield stress of the chann=
el<br>
&gt; material.<br>
&gt; <br>
&gt;=C2=A0 =C2=A0Fb =3D M*c/I<br>
&gt; <br>
&gt; [Ref 2] M for each web: PL/8 =3D P*120in/8 =3D P*15in [P is point load=
, lb]<br>
&gt; [email] c for each web: 1.5in<br>
&gt; [Ref 4] I for each web: (b*(h^3))/12 =3D ((0.5in)*(3in)^3)/12 =3D 1.12=
5in^4<br>
&gt; <br>
&gt;=C2=A0 =C2=A0Fb =3D (P*15in*1.5in)/1.125in^4 =3D P*20 lb/in^2<br>
&gt; <br>
&gt; For the given situation, p=3D3840lb, so Fb (max) is 3840*20 =3D 76800l=
b/in^2<br>
&gt; distributed between the two channels, each with two flanges. Since Fb<=
br>
&gt; must be less than the material yield stress, 10000 psi for some kind o=
f<br>
&gt; structural Al, but not high-strength material [Ref 3], this doesn&#39;=
t look<br>
&gt; very good. Each flange would be loaded to about 19200lb/in^2 if all<br=
&gt; loads were perfectly distributed. (Note that high-strength Al (e.g.<br=
&gt; 6061) can have a yield stress of 45000lb/in^2 so looks much more likel=
y<br>
&gt; to succeed, but I don&#39;t know how much I&#39;d trust that.)<br>
&gt; <br>
&gt; My biggest concerns would be the division of stresses between flanges<=
br>
&gt; (if one channel tilts a little or is not sitting perfectly flat on the=
<br>
&gt; trailer or ground, stress sharing will be uneven and one flange make<b=
r>
&gt; take all stress) and the potential for flange instability (see notes i=
n<br>
&gt; 1.3.1.5 in Ref 1.) This may not be a problem because the flanges are n=
ot<br>
&gt; particularly deep, but I watched a boat hung from I-beams drop when a<=
br>
&gt; structural I-beam twisted slightly from imperfect loading and the enti=
re<br>
&gt; structure quickly twisted into a totally unsupportive mess.<br>
&gt; <br>
&gt; References:<br>
&gt; 1 Beam stress/strain:<br>
&gt; &lt;<a href=3D"https://engineeringlibrary.org/reference/simple-beam-be=
nding-air-force-stress-manual" rel=3D"noreferrer noreferrer" target=3D"_bla=
nk">https://engineeringlibrary.org/reference/simple-beam-bending-air-force-=
stress-manual</a>&gt;<br>
&gt; <br>
&gt; 2 Beam force/reaction:<br>
&gt; &lt;<a href=3D"https://engineeringlibrary.org/reference/beam-forces-mo=
ments-air-force-stress-manual" rel=3D"noreferrer noreferrer" target=3D"_bla=
nk">https://engineeringlibrary.org/reference/beam-forces-moments-air-force-=
stress-manual</a>&gt;<br>
&gt; <br>
&gt; 3 Material properties:<br>
&gt; &lt;<a href=3D"https://www.engineeringtoolbox.com/properties-aluminum-=
pipe-d_1340.html" rel=3D"noreferrer noreferrer" target=3D"_blank">https://w=
ww.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html</a>&gt;<br>
&gt; <br>
&gt; 4 Area moments:<br>
&gt; &lt;<a href=3D"https://www.engineeringtoolbox.com/area-moment-inertia-=
d_1328.html" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.en=
gineeringtoolbox.com/area-moment-inertia-d_1328.html</a>&gt;<br>
&gt; <br>
&gt; ATB,<br>
&gt; Donald.<br>
&gt; --<br>
&gt; *Plain Text* email -- it&#39;s an accessibility issue<br>
&gt; () no proprietary attachments; no html mail<br>
&gt; /\ &lt;<a href=3D"https://www.georgedillon.com/web/html_email_is_evil.=
shtml" rel=3D"noreferrer noreferrer" target=3D"_blank">https://www.georgedi=
llon.com/web/html_email_is_evil.shtml</a>&gt;<br>
&gt; <br>
&gt; On 2021-07-01 10:56 p.m., john niolon wrote:<br>
&gt;&gt; I&#39;m thinking about using aluminum channel for a set of ramps f=
or my car<br>
&gt;&gt; hauler.=C2=A0 I have some &#39;available&#39; that is=C2=A0 10&quo=
t; wide with .50 web<br>
&gt;&gt; thickness and almost 3&quot; flange... about 15# per ft.<br>
&gt;&gt; =C2=A0<br>
&gt;&gt; ramps will be 7-8&#39; long =E2=80=A6..=C2=A0 and will go from gro=
und to 17&quot; high trailer<br>
&gt;&gt; deck...=C2=A0 truck weight is 5300 +/- =E2=80=A6 with front end we=
ighting 3840.=C2=A0=C2=A0 I<br>
&gt;&gt; can&#39;t find a table telling me weight capacity of<br>
&gt;&gt; channel with the load traveling up the wide web...=C2=A0=C2=A0 lik=
e this=C2=A0=C2=A0 any<br>
&gt;&gt; ideas on capacity ??<br>
&gt;&gt; =C2=A0<br>
&gt;&gt; Image87ABA31D<br>
&gt;&gt; =C2=A0<br>
&gt;&gt; thanks<br>
&gt;&gt; john<br>
&gt;&gt; =C2=A0<br>
&gt;&gt; =C2=A0<br>
&gt;&gt;<br>
&gt;&gt; _______________________________________________<br>
&gt;&gt;<br>
&gt;&gt; <a href=3D"mailto:[email-masked]" target=3D"_blank" rel=
=3D"noreferrer">[email-masked]</a><br>
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From: Donald H Locker <[email-masked]>
Date: Fri, 2 Jul 2021 09:11:50 -0400

Some central supports would certainly help. I think my bigger concern
(which a good central support would help) would be stress distribution
and channel twisting. If either of the channels tipped (due to
unbalanced loading or uneven ground) the loads would not be squarely on
the flanges and could twist the channel => bad bongos!

A central support the prevented twisting would be a great boon to
reliability, I expect.

I am NOT a structural engineer; all I've said could be wrong, so check
carefully. (But I'd probably try it myself, FWIW.)

Donald.

On 2021-07-02 8:42 a.m., Jeff Scarbrough wrote:
> I haven't done it on 35 years, but at least your equations look
> familiar.  I find that comforting.
> 
> On Fri, Jul 2, 2021, 06:34 Donald H Locker <[email-masked]
> <mailto:[email-masked]>> wrote:
> 
>     /\ <https://www.georgedillon.com/web/html_email_is_evil.shtml
>     <https://www.georgedillon.com/web/html_email_is_evil.shtml>>
> 
>     <https://engineeringlibrary.org/reference/simple-beam-bending-air-force-stress-manual
>     <https://engineeringlibrary.org/reference/simple-beam-bending-air-force-stress-manual>>
>     >
>     > 2 Beam force/reaction:
>     >
>     <https://engineeringlibrary.org/reference/beam-forces-moments-air-force-stress-manual
>     <https://engineeringlibrary.org/reference/beam-forces-moments-air-force-stress-manual>>
>     >
>     > 3 Material properties:
>     >
>     <https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html
>     <https://www.engineeringtoolbox.com/properties-aluminum-pipe-d_1340.html>>
>     >
>     > 4 Area moments:
>     >
>     <https://www.engineeringtoolbox.com/area-moment-inertia-d_1328.html
>     <https://www.engineeringtoolbox.com/area-moment-inertia-d_1328.html>>
>     >
>     > ATB,
>     > Donald.
>     > --
>     > /\ <https://www.georgedillon.com/web/html_email_is_evil.shtml
>     <https://www.georgedillon.com/web/html_email_is_evil.shtml>>
>     >
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From: Pat Horne <[email-masked]>
Date: Fri, 2 Jul 2021 09:16:21 -0500

You might want to consider adding supports under the center of the ramps so the effective length of the ramps is half of the overall length. 

Peace,
Pat

Pat Horne 
We support Habitat for Humanity

On Jul 2, 2021, at 5:18 AM, Donald H Locker <[email-masked]> wrote:

 Fb = M*c/I

References:
1 Beam stress/strain:

2 Beam force/reaction:

3 Material properties:

4 Area moments:

ATB,
Donald.

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