# Aggregator
This command is used to construct a SectionAggregator object which groups previously-defined UniaxialMaterial objects into a single section force-deformation model.
```tcl section Aggregator $secTag $matTag1 $string1 $matTag2 $string2 …… <-section $sectionTag> ```

secTag

unique section object integer tag.

$matTag1, $matTag2 …

previously-defined UniaxialMaterial Objects.

$string1, $string2 …

force-deformation relations corresponding to each section object. One of the following strings can be used.

P

axial force-deformation.

Mz

moment-curvature about section local z axis.

Vy

shear force-deformation along section local y-axis.

My

moment-curvature about section local y axis.

Vz

shear force-deformation along section local z-axis.

T

torsion force-deformation.

Iy

second moment of area about the local y-axis (optional, used for 3-D analysis).

<-section $sectionTag>

specifies a previously defined Section object (identified by the argument $sectionTag) to which these UniaxialMaterial objects are added to define a new Section object.

The ‘section Aggregator’ command does not introduce additional sensitivity parameters. However, sensitivity parameters can be defined for each force-deformation relation used in the section aggragator.