Expansion joint for electrical duct bank and vault.

[sngengtip]

I am looking for design guidance/details on expansion joints that can be used at intersection of concrete duct and electrical vault to prevent severing the conduits due to differential settlement during an earthquake.

Any recommendations are very much appreciated.

 

[SlideRuleEra]

If you are talking about electrical conduits encased in reinforced concrete, one way is to construct the entire ductbank (conduits with their electrical wiring, concrete & rebar) thru an opening (usually rectangular), in the wall of the vault. That is, the end of the ductbank is flush with the inside wall of the vault.

During a significant seismic event you may break the walls of the vault, but the electrical service has a reasonable chance of continuing to operate. We used this approach at electrical power stations where keeping the units running was more important that worrying about damaged vaults.

http://www.SlideRuleEra.net

 

[sngengtip]

SlideRuleEra:

Thanks for the recommendation. We have used similar method. I am looking for some kinda of coupling joints such that the vaults wall will not be damaged. We have 3 circuits of high voltage, underground transmission and distribution conduits, some are encased in concrete duct bank, that will sit above or next to a proposed highway tunnel.

Thanks.