Pinned Connection

[myAREforum]

Can someone confirm that the attached photo is a pinned connection and not a roller. Note the base.

[nata]

Can someone confirm that the attached photo is a pinned connection and not a roller. Note the base.

based to what I read on
http://web.mit.edu/4.441/1_lectures/...lecture13.html,
this connection looks pinned to me

[architectron]

I'd say it is a pinned connection.

The base is shaped that way to accommodate thermal expansion....I think.

[panna1234]

In roller support both Rotation and Translation is free.
In pinned connection Rotation is free but Translation is fixed.

If you at middle- it looks like rotation is free and translation is fixed. So I think its pinned connection.

[rkeetckt]

OK,... I actually took this picture earlier today. I am pretty positive it is a Roller connection.

Roller connections allow Rotation and Horizontal movement and restrains vertical movement.

Pinned connections Allow only rotation. They restrain Vertical and Horizontal.

Fixed Connections restrain all 3. Restraining rotation, and horizontal + vertical translation.

The curved surface on the bottom allows horizontal movement and the hinge allows rotation,... Thus it is a roller.

If the curved surface on the bottom were actuially bolted down, then it would be a pinned connection.

[architectron]

I'm not convinced that rocking is the same as rolling?

Isn't the rocking motion allowed by this base actually a kind of rotational movement?

A pinned connection allows a member to rotate but not translate.

[nata]

OK,... I actually took this picture earlier today. I am pretty positive it is a Roller connection.

Roller connections allow Rotation and Horizontal movement and restrains vertical movement.

Pinned connections Allow only rotation. They restrain Vertical and Horizontal.

Fixed Connections restrain all 3. Restraining rotation, and horizontal + vertical translation.

The curved surface on the bottom allows horizontal movement and the hinge allows rotation,... Thus it is a roller.

If the curved surface on the bottom were actuially bolted down, then it would be a pinned connection.

you might be right. At least according to this
http://images.google.com/imgres?imgu...26tbs%3Disch:1

scroll 3/4 down

[rkeetckt]

Yes. This is the same exact condition. Plus I attended David Thaddeus's seminar in NYC a few weeks ago, and he had the same connection, with and added animation to show the horizontal movement. It is very minimal, but it can move horizontally.

[kchutch]

Deffinitely a roller connection.

I just read the "Support and Connections" document linked by nata to suggest pin connection (really good article, btw, thanks for the link, nata) and right in the section on roller connections it pretty much calls out this exact condition; "Roller supports can also take the form of rubber bearings, rockers, or a set of gears which are designed to allow a limited amount of lateral movement." Don't be fooled by the presence of the pivot pin in the connection, it's just there to allow the connection to flex while moving laterally.