MFPA Leipzig does creep analysis for concrete structures
MFPA Leipzig has a long tradition of experimental and analytical investigations of concrete. Code-Aster is used since more than 5 years.
To respond to an increasing demand for measurement, calculation and prognosis of creep of concrete structures the capabilities of Code-Aster for creep analysis have been deeply evaluated and adopted. This was done with the support of Ingenieurbüro für Mechanik, Dr. Johannes Ackva.
Shrinkage and creep of concrete can change considerably the stress state in reinforments of concrete. Their foreseeing is therefore of great interest.
Comparision of direct solvers
The following 4 diagrams show the elapsed times for the direct solver(s) of Code-Aster (MULT_FRONT and MUMPS) and NX.Nastran. The MUMPS solver is employed with an "in-core" and with an automatic memory management. (It was detected only afterwards that in case of "in-core" the available RAM was slightly too small, so that swapping of data might have extended slightly the elapsed time.)
MULT_FRONT knows only the shared-memory parallelisation (OpenMP). The elapsed time is halfed when using about 3 or 4 processor cores.
MUMPS knows both, shared-memory (OpenMP) and distributed-memory (MPI) parallelisation. The results show that it is most effective to mix them: setting ncpu=2 and mpi_nbcpu=2 will always reduce the elapsed time compared to the same number of processors using only one of the both parallelisation methods (ncpu=4 and mpi_nbcpu=1 or ncpu=1 and mpi_nbcpu=4).
The direct solver of NX.Nastran uses shared memory.
Comparing the direct solvers MUMPS (Code-Aster) has the best performance, in particular when used with both types of parallelism. NX.Nastran shows the longest elapsed times.
Between the iterative solvers ELEMITER of NX Nastran is the fastest one. This must be taken with some reservation: Iterative solvers are less robust compared to direct solvers and have many weaknesses for example when mixing of element types.