I want to restrain only the compressive force in the boundary condition and eleminate the tensile reactions as the structure that I am modelling has very low strength in tension.
One easy way is to replace the boundary condition with a Connector. I usually use 'Bushing' connector for this type of work, and use 'Stop' option Lowerbound and Upperbound values to make it apply only 1 direction loads.
Alternatively you could use Tension only material as well. You could see the options in Materail>Elasticity>Elastic>
Thank you. The discussion submitted previously in eng-tips is about Nastran and very general. However I will try to use the connectors.. and then report later here the results.