FVAL

FVAL, NODE, FLab, InpLab, Value
Defines Large Mass (LM) force for base excitation problems.

SOLUTION: FE Forces

NODE

Node number at which the LM force is specified.

FLab

Structural force labels that specify the type and direction of the LM force. Valid structural force labels are listed below.

Force: Fx, Fy, Fz
Moment: Mx, My, Mz

InpLab

Label indicating whether the enforced data is a displacement, velocity, or acceleration input.

U	—	Displacement
VEL	—	Velocity
ACC	—	Acceleration

Value

The value of the LM force or a table name reference for tabular input. To specify a table, enclose the table name in percent (%) signs. Use the *DIM command to define a table.

Notes

The FVAL command applies a Large Mass (LM) force to the specified node. The command takes displacement, velocity, or acceleration as the input (InpLab) and converts them to a force that is applied as specified by FLab. To compute the LM force, it first converts the displacement and velocity time history into acceleration. It then multiplies the nodal acceleration by the large mass defined at that node with the MASS21 element. This applies a LM force to the node.

If you do not define a MASS21 element at the specified node, the command will not apply an LM force.

FVAL applies to a single node. However, you can issue this command multiple times to apply an LM force to more than one node.

If a velocity initial condition (IC) is specified at the node and the degree of freedom (DOF) at which FVAL is issued, the velocity IC is used to calculate force. If multiple loads are specified for the same node and DOF, the last FVAL that you issue overrides the previous ones. A step-applied FVAL with Value = 0 (or a tabular input with zero (0) entries) deletes an existing LM force at that node and DOF.

Do not use the residual vector method (RESVEC command) with FVAL. The rigid body mode present due to the specified large mass will restrict the residual vector calculation.