Seismic Expansion Joints

[jbjones2001]

My firm is located in an area where every building ends up in Design Category "D". We typically try to exhaust all options before using moment frames because of the IMF or SMF requirement for this Design Category.

Every now and then we will have a scenario where we want to split a building into two separate structures (expansion joint) due to building geometry, inadequate diaphragm strength, re-entrant corners, etc.

Which leads me to my question. When both or even one of these structures uses IMF or SMF the lateral deflections become a huge issue with regard to expansion joints.

Are expansion joints typically sized for inelastic displacements (i.e. using cd * elastic displacements)?

Example:
50 foot tall buidling(s)
building one displacement=2" w/ cd=5.5 yields delta=11
building two displacement=2" w/ cd=5.5 yields dela=11
per IBC building separation=sqrt((11^2)+(11)^2)=15.55


How do you deal with an expansion joint this large?

Any thoughts or experiences would be greatly appreciated

 

[MikeHydroPhys]

Lap jointed ?
MikeHydroPhys

mdshydroplane

 

[jbjones2001]

Although it is not ideal, a lap joint will work for the floor, but what about the walls?

 

[Thane]

Several companies make expansion joint covers that are designed to cover expansion joints (both seismic and thermal joints) in buildings and allow traffic across them. The covers are used anywhere that traffic is expected to cross the joint.

The following is the website of one company that makes Expansion Joint Covers.

http://www.balcousa.com/balcoexpansion/index.html

Hope this helps.

Thane

 

[jbjones2001]

Thanks for the web page. I've used similar joint covers in the past. I'm just trying to check my philosphy and approach about sizing expansion joints for inelastic displacments. Any additional thoughts or comments are greatly appreciated.