expansion joint?

[LOKSTR]

I need some explaination about how an expansion joint in steel warehouse type building( 1 storey) is treated? Specifically I need to know followings:

1. What is max. distance after which it is a must? On what basis this distance is estimated?

2. How the lateral wind/seismic load is distributed among the frames when expansion joint is present( assuming x- brace frame is located in exp. joint in addition to the perimeter)?

3. Is there any other design issues we have to take care of, if expansion joint is present?

Thanks

 

[AggieYank]

1. Different people use different limits for expansion joint locations, depending on the building layout and size. Some people will say every 200 feet, some higher, depending on intuition and experience. Sometimes it is controlled by firewall requirements, however in your case I can't imagine this would apply. Something I just came up with, and makes sense is:
If you can't get a certain width (we'll say 300 feet) of roof deck to have a diaphragm action, and need x-bracing in the middle of it (to break it up into 150 ft sections), its a good idea to put an expansion joint in. It seems like a bad idea to have a diaphragm spanning accross multiple braces (x-bracing) due to misc. stresses that would occur from different movements on each side of the middle x-bracing.

2. 3. The idea of an expansion joint is to create two separate buildings. Each building will need its own x-bracing or form of lateral stability.

 

[SlideRuleEra]

A discussion of expansion joints took place in this recent thread
thread507-128660
Here is a link to the document, "Expansion Joints in Buildings, Technical Report No. 65", recommended by jmiec

http://books.nap.edu/catalog/9801.html

http://www.SlideRuleEra.net

 

[UcfSE]

When we need an expansion joint in the roof we will use a deck angle with holes slotted in the exp. direction to transfer shear to the support while allowing for expansion of the roof deck. That helps to avoid having two frames directly next to each other.

 

[JAE]

UcfSE -
When you do this with the angle and slots - how do you handle the diaphragm chord forces at the near and far edges of the deck? Usually the chords (edge angles are what's normally used) are continuous and the deck is attached to both the slotted angles and to the chord...seems like a stress raiser to me. Just wondering how you handle it as we have struggled at times with this as well.