St is described as 'Tailored for 3D linear structural analysis, and the frame element includes options for Saint Venant torsion, warping torsion, geometric stiffness, and shear deformation. It has a growing element library that will include plane membranes, plates, shells, and brick elements'. There are eight alternatives to St for Windows, Mac and Linux. The best alternative is FRAMEWORK 2D+3D, which is free. Other great apps like St are MASTAN2 (Free), Analysis for Windows (Freemium), Structurix (Free) and Estru3D (Free, Open Source).
Solve plane problems with elements: bars, beams, triangulars and space problems with elements: bars, beams, rectangular element for the calculation of the board flex, triangular element for the calculation of revolution solid.
SourceForge presents the Estru3D project. Estru3D is an open source application. SourceForge provides the world's largest selection of Open Source Software. Structural analysis using the Stiffness Matrix method
SAS-CIVIL is intented as a finite elements menthod software, with application oriented to civil and structural engineer, it is designed in two modules, one for analisys and another for desing, all under GNU license.