4/1/2014 Structural engineering other technical topics - Pinned connection at base plate

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Pinned connection at base platethread507-316229

ben3929 (Civil/Environmental) 15Feb12

8:57

My client wants me to use a pinned connection at base of a crane frame. The frame base will be attached to a 6" depth ground slab concrete.The client wants the base connection to carry only axial force no moment. How can I support such connection (pure pinned) at the base usinganchor bolts. What is the methodology to make the base to act as pinned connection.

ToadJones (Structural) 15Feb12

9:11

most columns welded to thin base plates are considered pinned.

If the column is independent of the building columns (only supports crane girders) then you can use two anchor bolts placed "inside" the columnfootprint for a wide flange shape.

How heavy are you column loads? You are putting this on a 6" slab?

ToadJones (Structural) 15Feb12

9:13

if this question is related to your other post about prying action, you might be do some things that are not advisable for crane runways.

SteelPE (Structural) 15Feb12

9:15

In reference to your pinned connection problem.

You can never truly have a pinned connection at the base. You can also never have a fully fixed connection as well. All connection will develop

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4/1/2014 Structural engineering other technical topics - Pinned connection at base plate

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some fixity. I attended an AISC seminar where they stated that a pinned connection will develop a fixity of 0.4EI/L. This equation was based offsome assumption in the AISC for calculating K.

Our standard connection has 4 anchors in a square pattern at a given guage (5"-6"). For this type of connection we assume that the base ispinned. Never have had a problem with the type of structures that we design.

Now, having a crane on a 6" SOG may pose some other problems.

StrPE (Structural) 15Feb12

10:03

You may want to get AISC's Design Guide #7 for Industrial Buildings.

MiketheEngineer (Structural) 15Feb12

10:24

If you truly want a pinned connection - you could weld two vertical side plates to the base plate. Install you column. Drill a BIG hole through allthree and install a clevis pin.

I wouldn't fabricate in that order - but you get my drift. Of course it is pinned in only one direction!!

dik (Structural) 15Feb12

10:42

Mike... you should have suggested using a couple of smaller holes and a steel ball... 2 directions <G>. Now, just to tie it together to preventuplift...

Dik

amec2004 (Aeronautics) 15Feb12

12:46

You can refer to attached PDF file for the typical base plate configuration of 2-Bolt Pin, 4-Bolt Pin and Moment Connection anchor bolt pattern.

You can check http://www.civilbay.com for a complete calculation of Pin and Moment Connection type base plate design as per AISC designguide 1, and anchor bolt design as per ACI 318-08 Appendix D

hokie66 (Structural) 15Feb12

16:44

As Mike said, you only get a true pinned connection if there is a PIN. The connections in amec2004's post which are called pinned connectionsare assumed pinned in design, but still resist some moment.

amec2004 (Aeronautics) 15Feb12

18:10

http://fi les.engineering.com/getfi le.aspx?folder=37b631b2-946a-4f5d-9acb-19

4/1/2014 Structural engineering other technical topics - Pinned connection at base plate

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That's true.

In reality there is no 100% pin, and there is no 100% fix. The actual condition is something in between.

Depends on the bolt pattern you go for, the 2-Bolt Pin and 4-Bolt Pin allows more rotation, say 20~30% fix and 70% pin, while anchor boltspreading out can restrain more rotation, say 70% fix and 20~30% rotation.

If you want to go for the ideal world, you can apply a rotation spring for that.

In the reality, we just go for above posted anchor bolt pattern and assume its 100% pin or fix in the model.

hokie66 (Structural) 15Feb12

21:23

amec2004,

That works fine for many structures, but in the OP's case, it sounds like he really wants to avoid transmitting any moment. If that is the case, hecan design a connection where a pin passes through gusset plates, allowing free movement in one plane. If he had to allow free movement in allplanes, he would have to use something like a universal joint, but that condition is almost never encountered in building structures.

amec2004 (Aeronautics) 15Feb12

22:01

Attached picture shows one example of true pin connection.

Just being relax on the 2-Bolt Pin or 4-Bolt Pin base plate actually carry some moment.

Do you think in steel structure the PIN connections (shear tab, clip angle, end plate etc) are really PIN ? They are not ! In STAAD or RISA modelwe all have member release to release moment restraints at member end but actually those PIN connections carry moment and impose a torsionto the connecting girder ...

chicopee (Mechanical) 15Feb12

22:24

mill3929, Am I assuming that you are referring to a tower crane and not a jib?

amec2004 (Aeronautics) 15Feb12

23:27

Most Jib crane is a single column with cantilever beam, the base is fixed ...

hokie66 (Structural) 15Feb12

23:50

http://fi les.engineering.com/getfi le.aspx?folder=dca33dc3-4b3b-4c0d-977c-33

http://fi les.engineering.com/getfi le.aspx?folder=14fdb78d-a9aa-4cf4-9930-e1

4/1/2014 Structural engineering other technical topics - Pinned connection at base plate

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amec,Yes, that Detail 3 is the type connection MiketheEngineer suggested, and it could be used at the base of a crane column. I don't believe anyonesaid this was a jib crane.

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