Element records

These records specify a description of particular elements. The general format is following:

*ElementType (num#)(in)
mat #(in) crossSect #(in) nodes #(ia)
[bodyLoads #(ia)] [boundaryLoads #(ia)]
[activityltf #(in)] [lcs #(ra)]
$ \langle$[partitions #(ia)]$ \rangle$ $ \langle$[remote]$ \rangle$

The order of element records is optional, the element number is determined by (num#)(in) parameter. The numbering of individual elements is arbitrary, it could be even non-continuous. In this context, one could think of element number as a label that is assigned to individual elements and by which the element is referenced. In parallel mode, the label represents a global id across all partitions.

Element material is described by parameter mat, which contains corresponding material record number. Element cross section is determined by cross section with crossSect record number. Element dof managers (nodes, sides, etc.) defining element geometry are specified using nodes array.

Body load acting on element is specified using bodyLoads array. Components of this array are corresponding load record numbers. The loads should have the proper type (body load type), otherwise error will be generated.

Boundary load acting on element boundary is specified using boundaryLoads array. The format of this array is

$\displaystyle 2\cdot size \; lnum(1)~id(1)~\dots~lnum(size)~id(size),

where $ size$ is total number of loadings applied to element, $ lnum(i)$ is the applied load number, and $ id(i)$ is the corresponding entity number, to which the load is applied (for example a side or a surface number). The entity numbering is element dependent and is described in element specific sections. The applied loads must be of proper type (boundary load type), otherwise error is generated.

The support for element insertion and removal during the analysis is provided. One can specify optional time function (identified by its id using activityltf parameter). The nonzero value of this time function indicates, whether the element is active (nonzero value, the default) or inactive (zero value) at particulat solution step. Tested for structural and transport elements. This feature allows considering temperature evolution of layered casting of concrete, where certain layers needs to be inactive before they are cast. See a corresponding example in oofem tests how to enforce hydrating material model, boundary conditions and element activity acting concurrently.

Orientation of local coordinates can be specified using lcs array. This array contains six numbers, where the first three numbers represent a directional vector of local x-axis, and the next three numbers represent a directional vector of local y-axis. The local z-axis is determined using the vector product. The lcs array on the element is particularly useful for modeling of orthotropic materials which follow the element orientation. On a beam or truss element, the lcs array has no effect and the 1D element orientation is aligned with the global $ xx$ component.

The remote forces the element to be remote element. Remote element does not contribute to local partition governing equation. They are introduced in order to implement band of elements involved in computation of nonlocal variables (see fig. 6.7 illustrating this approach for node-cut partitioning). They role is to provide local mirror of corresponding remote partition element integration point values which undergo nonlocal averaging on local partition.If not used, element is assumed to be local partition element. When remote is used, the partitions parameter should contain remote partition number, where corresponding element is local (this array should have size equal to one).

Available material models, their outline and corresponding parameters are described in separate Element Library Manual.

Borek Patzak