Next: *STEP Up: Input deck format Previous: *SOLID SECTION Contents

##
*STATIC

Keyword type: step

This procedure is used to perform a static analysis. If no perturbation parameter was specified in the *STEP card the load consists of the sum of the load of the last *STATIC step and the load specified in the present step with replacement of redefined loads. If the perturbation parameter was specified (makes sense for *FREQUENCY and *BUCKLE steps only), all loads previous to the step are removed and the only active loads consist of those specified in the present step (for *BUCKLE steps only; for *FREQUENCY steps no loads are taken into account). However, the displacements and stresses at the start of the step are taken into account in the stiffness matrix.

There are two optional parameters: SOLVER and DIRECT. SOLVER determines the package used to solve the ensuing system of equations. Default is SPOOLES, denoting the SPOOLES solver [2,3]. Alternatively, the PROFILE solver listed in [27] can be selected (SOLVER=PROFILE), or the iterative solver by Rank and Ruecker [20], which is based on the algorithms by Schwarz [21]. If SOLVER=ITERATIVE SCALING is selected, the preconditioning is limited to a scaling of the diagonal terms, SOLVER=ITERATIVE CHOLESKY triggers Incomplete Cholesky preconditioning. Cholesky preconditioning leads to a better convergence and maybe to shorter execution times, however, it requires additional storage roughly corresponding to the nonzeros in the matrix. If you are short of memory, diagonal scaling might be your last resort. The iterative methods perform well for truely three-dimensional structures. For instance, calculations for a hemisphere were about nine times faster with the ITERATIVE SCALING solver, and three times faster with the ITERATIVE CHOLESKY solver than with SPOOLES. For two-dimensional structures such as plates or shells, the performance might break down drastically and convergence often requires the use of Cholesky preconditioning. SPOOLES performs well in most situations with emphasis on slender structures but requires much more storage than the iterative solver.

The parameter DIRECT is relevant for nonlinear calculations only, and indicates that automatic incrementation should be switched off.

First line:

- *STATIC
- Enter any needed parameters and their values.

Second line (only relevant for nonlinear analyses)

- Initial time increment. This value will be modfied due to automatic incrementation, unless the parameter DIRECT was specified (default 1.).
- Time period of the step (default 1.).
- Minimum time increment allowed. Only active if DIRECT is not specified. Default is the initial time increment or 1.e-5 times the time period of the step, whichever is smaller.
- Maximum time increment allowed. Only active if DIRECT is not specified. Default is 1.e+30.

    Example:

    *STATIC,DIRECT
    .1,1.

defines a static step and selects the SPOOLES solver as linear equation solver in the step (default). If the step is a linear one, the other parameters are of no importance. If the step is nonlinear, the second line indicates that the initial time increment is .1 and the total step time is 1. Furthermore, the parameter DIRECT leads to a fixed time increment. Thus, if successful, the calculation consists of 10 increments of length 0.1.

Example files: beampic, beampis.

Next: *STEP Up: Input deck format Previous: *SOLID SECTION Contents