Tekla 21.1 System Requirements -

Tekla 21.1 handles rebar as individual objects. A 20-story concrete tower with #4 rebar can require 28 GB of RAM just to open the model. If you have 16 GB, the system will crash upon assigning bar numbers.

Microsoft .NET Framework (typically version 4.5.1 or later for this era) tekla 21.1 system requirements

Tekla 21.1 reached End of Life (EOL) before Windows 11 launched. While it installs on Win 11, the OpenGL translation layer causes random crashes during numbering. Stick to Windows 10 for 21.1. Tekla 21

: You must install both x86 and x64 versions of: Microsoft Visual C++ 2010 Microsoft Visual C++ 2013 Microsoft Visual C++ 2015 Licensing and Compatibility tekla 21.1 system requirements