Is there a free alternative to CYPE 3D, SAP2000 or Robot Structural?

Yes — CalcSteel is a free web-based alternative specifically focused on steel structures. It replaces the core 3D frame analysis workflow of commercial packages: you model a structure, apply loads, run FEM analysis, check profiles against design codes, and export a PDF report. Unlike CYPE or SAP2000, CalcSteel runs in the browser with zero installation. The free tier includes 3 projects, 3 sheets per project and 25 analyses per month. For unlimited projects and analyses you upgrade to Pro ($24/month annual). If you're coming from CYPE 3D looking for a cost-effective option, CalcSteel covers 90% of typical steel frame workflows at 0-2% of the cost.