Expansion joint/movement joint in g+2 building

[sfat]

I'm designing a factory building whose dimensions are 100' x 400'. It's a concrete moment resisting frame. No shear walls. I've provided an expansion joint dividing the building in two parts of 100'x200'. When I calculated in-elastic displacement "delta M" for two buildings and calculated the joint width as per IBCcode , it's coming around 9 inches wide which seems too much for a G +2 building in seismic zone 2B. Architect is not willing to provide this wide joint as only an inch or 2 in wide joints are in common practice . Want to know how much widths other engineers have provided. Anybody experiencing same difficulty? Am I calculating the right way?

 

[civilsalman]

What you have calculated is the seismic seperation required for the building structures. i think you can go safely by providing 2 to 2.5 inches expansion joint in G+2 building structures. In order to estimate actual required width of expansion joint browse the literature.

Regards

 

[JAE]

Was this the direct sum of the two deflections added together? ASCE 7 allows the use of square root of the sum of squares (SRSS) for the gap deflection.

I would be reluctant to reduce the gap just due to the building type (g+2). The two sections would still hammer together in a seismic event and people to occupy such buildings.

Perhaps you can also try to stiffen the building to minimize deflections. How tall is it?

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[sfat]

value I got is SRSS. Building is 48ft above ground. Bays are 32'x50'.

 

[sfat]

Just wondering if I can avoid joint and can do single building with couple of pour strips in 400' span....

 

[JAE]

9" joint in a high seismic area seems reasonable. But not sure about SDC B areas. That seems high but you are 48 feet above grade.

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[sfat]

Thanks JAE! It's Sdc C area. Any thoughts on avoiding joint??is it doable to go for 400' span without joint??

 

[JAE]

400 feet is pushing it. But I would think it is possible. The concern would be long term concrete shrinkage creating tension in the horizontal members (shrinkage pulling against the moment frames down the line) and thermal movements at the far ends (if there are any significant changes in the temperature of the "interior" concrete sections.

Also - potential foundation settlements would also affect the framing but that is true with the expansion joint as well as without.



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