About CalculiX

CalculiX is most popular FEA open-source package. Good for structural, mechanical, thermal and fluid applications (trusses, plates, frames, shells, solid bodies). It has powerful nonlinear capabilities (including tension/compression only material like concrete) and most types of analysis (modal, buckling, etc) .

See home page at

http://calculix.de/

http://www.dhondt.de

Another windows version

http://www.bconverged.com/