Starred angle properties
Starred angle properties
(OP)
Hi all,
I am looking for the formulars to calculate the J (torsional constant) and Cw (warping constant)for the starred angle compression member (See attachment). Can anyone point me to the right directions or resources? Does a starred angle shape be considered as a single or double symmetrical shape? I assume it is a double symmetrical shape. Is my assumption right or wrong? Thank you in advanced.
I am looking for the formulars to calculate the J (torsional constant) and Cw (warping constant)for the starred angle compression member (See attachment). Can anyone point me to the right directions or resources? Does a starred angle shape be considered as a single or double symmetrical shape? I assume it is a double symmetrical shape. Is my assumption right or wrong? Thank you in advanced.






RE: Starred angle properties
Usually, there was a gap equal to the thickness of the plate, in the perpendicular direction for alternating direction gusset plates. With equal legged angles, that gave two axes of symmetry, diagonal in your picture.
With your layout I see only polar symmetry.
I don't know about torsional values, but angles have negligible torsional stiffness.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Starred angle properties
http://www.iesweb.com/downloads/index.htm
If you need it in a hurry, post the angle sizes and I can run it for you.
RE: Starred angle properties
RE: Starred angle properties
You can see the formulae on which they are based by clicking on Options -> Show formulae
prex
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RE: Starred angle properties
Respect how to get the sectional properties for a notional + section, you can look at
Design of Steel Structures
Gaylord, Gaylord, Stallmeyer
3d edition
McGraw Hill 1992
Example at p. 268
where
J=(4/3)*(b*t^3)
Cw=(b^3*t^3)/9
b is the width of just an angle, t its common thickness
Except finding the averaged equivalent sectional properties somewhere, that must exist since in the end this was a practical structural member sometimes used, we enjoy today the luxury of 3D FEM models able to properly portrait member, forces and constraints, and this could help where some application like this can become particularly critical for the determination of stresses and displacements.
RE: Starred angle properties
Thanks a lot for the links.
RE: Starred angle properties
RE: Starred angle properties
In your post you have J = (4/3)*(b*t^3). I think you included the 4 is because you have 4 angles, correct?
According to AISC Design Guide 9 on torsion, for sections composed of rectangular shapes with b/t > 10
J = SUM (1/3)*b*t^3)
where t is the thickness and b is the width of the individual rectangle shapes.
DG#9 as specifies that if b/t < 10 then
J = (1/3 -0.2t/b)*b*t^3.
By the way Desgin Guides can be downloaded for free from AISC's web site, if you are a member.
DHKpeWI
David
RE: Starred angle properties
In your post you have J = (4/3)*(b*t^3). Is this formula specific to this cross section? Is the 4 included because there are 4 angles?
To all:
According to AISC Design Guide 9 on torsion, for sections composed of rectangular shapes with b/t > 10:
J = SUM (1/3)*b*t^3)
where t is the thickness and b is the width of the individual rectangle shapes.
DG#9 specifies that if b/t < 10 then:
J = SUM (1/3 -0.2t/b)*b*t^3.
By the way the Design Guides can be downloaded for free from AISC's web site, if you are a member.
DHKpeWI
RE: Starred angle properties
RE: Starred angle properties
As a composite section, it is close to a cruciform shape, which is doubly symmetric (not sure of the significance of that fact). J and Cw remain the same as above.
BA