NESC0641 SAP4.

SAP4.

SAP4 is a structural analysis program for determining the static and dynamic response of linear systems. The structural systems to be analyzed may be composed of combinations of a number of different structural elements. Currently the program contains the following element types:

1. three-dimensional truss element,

2. three-dimensional beam element,

3. plane stress and plane strain element,

4. two-dimensional axisymmetric solid,

5. three-dimensional solid,

6. variable-number nodes thick shell and three-dimensional element,

7. thin-plate or thin-shell element,

8. boundary element,

9. pipe element (tangent and bend).

The formation of the structure matrices is carried out in the same way in a static or dynamic analysis. The static analysis is continued by solving the equations of equilibrium followed by the computation of element stresses. In a dynamic analysis the choice is between frequency calculations only, frequency calculations followed by response history analysis, frequency calculations followed by response spectrum analysis, or response history analysis by direct integration. To obtain the frequencies and vibration mode shapes, solution routines are used which calculate the required eigenvalues and eigenvectors directly without a transformation of the structure stiffness matrix and mass matrix to a reduced form. To perform the direct integration an unconditionally stable scheme is used, which also operates on the original structure stiffness matrix and mass matrix. In this manner the program operation and input data required for a dynamic analysis are simple extensions of those needed for a static analysis.

The capacity of the program depends mainly on the total number of nodal points in the system, the number of eigenvalues needed in the dynamic analysis, and the computer used. There is practically no restriction on the number of elements used, the number of load cases, or the order and bandwidth of the stiffness matrix. Each nodal point in the system can have from zero to six displacement degrees of freedom. The element stiffness and mass matrices are assembled in condensed form.
Therefore, the program is equally efficient in the analysis of one-, two-, or three-dimensional systems.

Execution times vary with the problem being solved and the computer resources requested. Typical problems may require 5 to 10 minutes.

SAP4 is one edition of the SAP series of programs. Earlier editions were designated SAP2 or SOLIDSAP and SAP3. This edition includes a new variable-number nodes thick shell and three-dimensional element and permits out-of-core direct integration for time-history analysis. The original SAP4 program, a CDC version, was obtained from the Earthquake Engineering Research Center, University of California at Berkeley.

• S. Zawadzk: Notes on Argonne's Version of the Structural Analysis Program SAP4,
  ANL-AMD Memorandum, February 9, 1978, Revised September 11, 1981

• SAP4, NESC No. 641.370F, Contents of SAP4 Transmittal Tape, National Energy Software Center Note 82-02, October 13, 1981.

The computer resources required depend on the type of problem, and trade-offs are selectable to an extent. Storage needs may vary from 250K to 2000K bytes. Peripheral device usage has been optimized for static analysis and step-by-step integration.

OS/360,370.
MVS (IBM 3081).

Three local Argonne routines are called by SAP4. NOFLOW suppresses underflow messages; it may be replaced by a call to ERRSET. TLEFT is called with one dummy argument which returns to the calling program the difference, in hundredths of a second, between the user's time estimate for the job and the elapsed time, i.e., the time left. DCUBRT computes the double-precision cube root of a normalized, double-precision, floating-point argument.

S. Zawadzki
Applied Mathematics Division
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439, USA