Couplers in shear walls

[rcampbell]

Under what conditions are couplers required in lateral elements to resist lateral loading (wind loads)?

My understanding is that lateral loading induces flexural tension into the core (lateral resisting element in this case) and hence as this is not defined as direct tension in AS3600 (i believe the ACI code defines it similarly) that lapping of reo is permitted. However i have just reviewed a building (55 stories) that has couplers which seems strange.

My first thoughts were that the core was designed using the rectangular stress block theory which would hence require couplers to be used, is this correct?

My second thought was that under service winds if the core still experiences tension then not only is the core severly under sized but this would induce regular cyclic loading into the core and hence couplers would be required, but to be honest i am just not sure.

Anu assistance would be greatly appreciated.

Ryan.

 

[sdz]

Do you mean mechanical couplers are used to join reinforcing bars instead of a lap splice?

If so then there can be several reasons why they are being used.

First they eliminate long laps in both tension and compression.
They also reduce congestion and cranked bars.
Finally if the section is indeed in tension then the designer may have decided that the stress in that element acts more like a direct tension than a flexural tension - and this could be the correct decision if, say, a whole wall panel was in tension.