Diamonds is described as 'The perfect software for structural design analysis of beam grids, floor slabs, rafts, walls, frames and multi-storey buildings, ... in concrete or steel. Development of calculation engineering design software with powerfull tools en simple user' and is an app. There are more than 50 alternatives to Diamonds for Windows, Linux, Web-based and Mac. The best Diamonds alternative is Robot Structural Analysis Professional. It's not free, so if you're looking for a free alternative, you could try SkyCiv or SkyCiv Structural 3D. Other great apps like Diamonds are Etabs, SAP2000, RISA-3D and CloudCalc.