Slotted Hole Conncection 1

[Vivek19]

Hi,

I am in need to connect a new steel structure to an Existing steel structure with a beam. But the beam hast to transfer only the Gravity Force not the Lateral force.

I have to choose the slooted hole connection. But I am not aware of the Slotted hole connection in both the lateral directions. ( Both X & Z Direction are lateral , Y is in Vertical ).

Anybody can help me to fix the Slotted hole connection in 2 directions.

With Regards,
Vivek

 

[ishvaaag]

By not fixing the direction perpendicular to the web you are getting into trouble. Normally if you need such mobility you will do better with some sliding bearing plate, to be supported by a corbel. You may study the specialty items, with plates bearing in pots where the horizontal movements are limited, and even the vertical ones can be quite efficiently prevented, upwards as well.

 

[csd72]

Yes, you need the lateral froce restraint to prevent buckling of the beam. It may be easier just to calculate what the worst load is that could be induced and allow for it in the calculation of your beams.

What is the exact reason why you need to isolate the two? Is this a seismic zone?

 

[Vivek19]

As per the Client's requirement , I need not to transfer the lateral forces to the existing building.
I need to insure full movement in both mutually perpendicular axes NS/EW at interface connection to the existing Building.

 

[Vivek19]

Sliding seated connection .. it is the one I need to use..

 

[hokie66]

Glad you have decided against the slotted hole connection. Slotted bearing connections are notorious for locking up and causing all sorts of failures.

Suggest you provide your requirements to a slide bearing manufacturer.

 

[csd72]

vivek19,

you still didnt really answer my question. Is your client more aware of structural implications than you? If so then why are they employing you? if not then why are they dictating design philosophy?

No problems if there are good reasons to agree with this but if this is the case then it would be good to understand the reasons. There may actually be situations where 2 separate lateral systems would cause more problems than it solves.

 

[Vivek19]

Hi csd72 ,


The existing structure is a Process structure. And the new one is also a process structure. In the existing structure so many sensitive equipments are there. because of that , we are forced not to transfer the lateral loads either direction.

 

[csd72]

aah, sorry for the bluntness of my last post but this is the type of pertinent information needed to make a satisfactory comment.

If they are two process structures with vibrating machinery then you may want to consider completely isolating the two rather than jointing them in any way. That way any vibrations in one will not induce vibrations in the other.

Slotted holes are not really suitable for isolating vibrations.

 

[delagina]

one thing you need to remember it is standard to use pre-tensioned bolts (dti) in oil and gas/petrochemical process structures. so you would still be transferring horizontal loads even if you use slotted holes not unless you specify finger tighten double nut.

also if your structure is too high you may want to consider the deflection/drift of column/strucuture, so you can size your slotted hole correctly to not transfer lateral load.

 

[ToadJones]

Can you isolate the new structure entirely and use an expansion joint?

 

[dik]

You can use an oversized hole, not as good as a long slot, but provides some adjustment.

Dik

 

[hokie66]

csd72 and ToadJones are correct. With sensitive process equipment involved, you probably need to make the new building a separate structure by using separate columns. Any type bearing connection will transmit vibrations. In industrial structures, the cost of the structure itself is usually a minor component...saving a few dollars initially usually leads to long term grief.

 

[ToadJones]

Hokie-
Line of the day goes to you:
"...In industrial structures, the cost of the structure itself is usually a minor component...saving a few dollars initially usually leads to long term grief...."

From my experience, usually the owners recognize this too. I have been asked more times about "under designing" something as opposed to "over designing" when it comes to heavy industrial facilities.
Shut-downs and down time cost these facilities millions of dollars sometimes on a daily basis. Owners want these facilities up and running period.

 

[hokie66]

Amen. In the industrial environment, I have never been called to task for making something too robust. When you go into a plant and see a column sheared off at the base and twisted 90 degrees, yet everything is still standing, you realize you have to allow for rough treatment.