This is the biggest risk. "Portable" executable files (.exe) found on cracking sites are often bundled with trojans, miners, or ransomware. Since you are running the file as an administrator, these viruses can steal your data, passwords, or lock your files.
The popularity of the portable version boils down to three main factors:
You're looking for a cracked or portable version of STAAD Pro, a popular structural analysis and design software. I must remind you that using pirated or cracked software can be against the terms of service and potentially harmful.