# Reduction of values near supports

For plate and shell elements supported at points or by linear supports (by means of the available support types, columns or walls), values of moments and stresses near the support points may be considerably greater than at the remaining points of the plate. This may cause calculation of incorrect reinforcement in the vicinity of supports and columns. To avoid this, such connections can be modeled either by means of the available rigid links or by applying Reduction of forces above columns and walls.

Reduction of values near supports replaces the result values obtained in the vicinity of supports, columns and walls with the reduced value from the vicinity of these supports. Three stages are distinguished in this operation.

Definition of support nodes. Values are reduced only near supported defined as follows.

• A column type support (rectangular or round) with non-zero dimensions - See advanced parameters for supports.
• A linear support on the edge or on a polyline. This support is defined as a wall in advanced support parameters.
• Bar elements are connected with finite elements. This is only when the other bar end is not connected with the same finite element as it is the case for a strengthening beam. For a node to be considered as supported, it must be adjoined by at least one finite element.
• Planar elements of the horizontal panel meet with planar elements of the adjoining perpendicular panel (a vertical wall in the Z direction) on a horizontal panel (a slab in the XY plane).

At nodes where supports at points and beam supports (without dimensions) are defined, values are not reduced.

• Definition of a reduction radius - If reduction of selected values is performed at a given node, then it should be determined which values should be disregarded. The values ignored include the values at this node and at centers of elements that adjoin this node. The software searches for nodes positioned in the distance lesser than the reduction radius; values at these nodes will also be disregarded and replaced with the calculated average value. The reduction radius is determined in the following manner.
• Supports defined at a node - Reduction radius equals half the length of the diagonal of a rectangular support or half a diameter of a round support.
• Columns adjoining to a node - Reduction radius equals half the length of the diagonal of a rectangle with dimensions equaling the column width and height.
• Linear supports / walls - Reduction radius equals half the wall thickness.

If one node is adjoined by several supports with different values of reduction radiuses, then the greatest of the calculated radiuses is adopted in calculations.

• Calculation of the reduced value - When the reduction radius value is calculated, the result values in nodes positioned in the distance (from the supported node) lesser than the determined radius value and in centers of finite elements that adjoin them are disregarded. These values are replaced with the reduced value of the results on the edge of the disregarded region. When calculating this value, the averaging parameters are taken into account. If a node is adjoined by an element and at least one of this element's nodes lies inside the reduction circle, then a value from this element is also ignored while averaging. The reduced value is calculated applying the following principles.
• If values at all nodes on the edge are positive, then the maximal value is adopted.
• If values at all nodes on the edge are negative, then the minimal value is adopted.
• If values on the edge show different signs, then the average value is calculated and that value is assumed as the reduced one.

When the reduced value is calculated, it substitutes all disregarded values in the vicinity of a given support node.

NoteThis option should be used with caution. Consider the map of moments obtained after reduction. The option works correctly if dimensions of the column (support) cross section are comparable to dimensions of the mesh of planar finite elements. If column dimensions are far greater than dimensions of FE mesh, it is recommended to define other dimensionless supports around the support with the dimension or to define rigid links.