pinned connections in trusses
pinned connections in trusses
(OP)
Its been a while since I've had to do structural detailing and from my dim memory of truss design in college I seem to remember that if the centrelines of all the members at a joint intersect then the joint has no moment capacity - i.e is a pinned joint. Is this right?






RE: pinned connections in trusses
The type of connection at the joint determines whether they are pinned or fixed (moment).
RE: pinned connections in trusses
RE: pinned connections in trusses
in reality the connection is a multiple pin arrangement (therefore capable of reacting moment) and offset from the neutral axis (of at least some members) therefore inducing bending in the strut (the load axis isn't aligned to the strut). in reality these two effects are usually small enough to be neglected.
to answer the OP, the strut axes may meet at a point and the struts can, or cannot, react moment depending upon the attachment between the struts (whether it is a single pin or a multiple pin).
RE: pinned connections in trusses
RE: pinned connections in trusses
RE: pinned connections in trusses
RE: pinned connections in trusses
Sorry about that.
RE: pinned connections in trusses
Regards,
-Mike
RE: pinned connections in trusses
In your post I would say instead that "if your members are not deep" you should be able to neglect secondary stresses due to moments. I would however be very careful with any eccentricities caused by centerlines not intersecting at a point.
-Mike
RE: pinned connections in trusses
RE: pinned connections in trusses
RE: pinned connections in trusses
www.SlideRuleEra.net
RE: pinned connections in trusses
In fact those moments give rise to secondary stresses (as they are called in pressure vessel analysis). Such stresses are not load controlled quantities, instead they are deformation controlled quantities: the distortions they cause will tend to decrease them, and even if they reach the yield condition, they will stay there and no more increase (whilst a primary stress, if the external loads increase, will increase till the structure collapses).
Our grandfathers didn't know the theory behind that, but that's why the truss method of analysis works so well.
prex
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RE: pinned connections in trusses
RE: pinned connections in trusses
RE: pinned connections in trusses
However if a Vierendeel type arrangement is used then the members should be designed to resists axial load, moments, and shears.
VB