**surface_load

Description

This boundary condition apply load forces on boundary sets (lines, surfaces). If a force \(F_{ext}\) is applied, the following reaction force \(F_i\) will be applied on each node \(i\):

(42)\[F_i = \dfrac{F_{ext}}{A}\int N_i dA\]

where \(A\) is the surface or the length of the boundary set and \(N_i\) is the corresponding shape function.

Syntax

**surface_load \(~\,~\,\) bset_name  (dir) [exp]  value  table_name

bset_name

This is the name of a valid boundary set (bset) on which the surface load is applied.

dir

is the force direction.

exp

is an optional keyword to indicate the boundary condition will expire.

value

This real value acts as a multiplier on the current applied load table value. If the value is zero, no table will be required.

table_name

A character name for the loading table which describes the DOF value in time. A corresponding table must therefore be given elsewhere (see the procedure ***table).

Example

***bc
  **impose_nodal_dof
    bottom U2 0.
    1 U1 0.
  **surface_load top (0. 1.) 1000. time

If this boundary condition is applied to a quadratic c2d8 element, the vertex nodes will each take one-sixth of the applied force, while the middle node will take two-thirds.