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When defining \\

A variety of *confinement* options are available to *Caltrans circular sections in * that are defined using the [Section Designer|kb:Section Designer], theincluding usercasings canand define hoop or spiral confinementtransverse reinforcement.

h4. andConfinement alsooptions
define
casingThe forconfinement thewithin entire section. There are the following options forreinforced-concrete sections may be modeled using any of the confinedoptions concretewhich modelfollow:

* *Core* applies -the thisMander optionconfined-concrete willmodel utilizeusing theeither hoop or spiral confinementtransverse reinforcement.
as
the* confinement*Casing* reinforcementalso forapplies the Mander concrete model, *though Casingthe -casing thisis option will convert the casing converted into equivalent hoop reinforcement.
and
use as the confinement reinforcement for the Mander concrete model
* Mander(C) - this option allows the user to specify custom parameters for* *Mander(C)* allows manual specification of the constitutive parameters which characterize the Mander confined-concrete model.


h4. Casing with transverse reinforcement

Since the Mander concrete model only Itdistinguishes isconfined notand possibleunconfined toconcrete, includeand bothnot themultiple hoopconcentric orregions spiralof confinement, reinforcement andboth the casing as confinement reinforcement for and the Mandertransverse concretereinforcement model,may becausebe themodeled standardas Manderfollows:
model,
does# notDetermine explainthe howmaterial tobehavior accountof foreach multiple diameters of confinementconfined region.
The\\
user\\
would# have to decide what Use the net effect is, and define their own equivalent material using Mander(C). The standard Mander model only applies to a single perimeter of circular or rectangular confinement.

For example, suppose the casing is quite substantial and the inner hoops are not so big. All of the concrete would be confined by the casing and the inner hoops would not be able to develop significant restraint until the casing Mander(C) option to define materials which simulate an equivalent effect.
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# Assign these materials to the corresponding regions of confinement.


h4. Best practice

* *Structural casing* -- When the casing contributes substantially to structural behavior, it is often sufficient to model only this layer as the confinement mechanism since the inner transverse reinforcement will only provide significant contribution once the casing has failed, at which point, thecrushing inneroccurs hoops would likely fail too. The inner hoops would essentially be irrelevant to the overall behavior. This is the most likely scenario, and the casing model would apply to the entire section. Oftenand the hoops or spiral reinforcement will likely fail as well. In this case, inner transverse reinforcement is essentially irrelevant to overall performance. Such applications may occur when casing is added to an existing section that is known to be underconfined or inadequate.

* *Decorative 
On the other hand, the casing could be largely decorative and the inner hoops provide the main confinement, in which case using Core1 for the inner concrete would make the most sense.

If the user expects something different, it is up to them to determine the equivalent confinement and apply it to the two concrete regions appropriately using the standard Mander(C) modelcasing* -- When the casing does not serve a structural function, and instead offers only a decorative layer, or formwork for the concrete pour, the inner transverse reinforcement acts as the primary confinement mechanism. In this case it is best to assign the Core option and apply the conventional Mander confined-concrete model in which only the transverse reinforcement provides confinement. 

* *Casing with transverse reinforcement* -- If multiple regions of confinement are to be modeled, the appropriate material behavior must be determined, then manually defined and applied using the Mander(C) option.

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*Related Incidents:*

* {incident:no=49183|comment=Section designer confinement reinforcement}
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** {email:date=11/19/2012|from=bm|to=ok|subject=Section designer confinement reinforcement|comment=|id=9896195}
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