Hi,
The code API 650, didn't mention how to calculate allowable stress in case of platforms, walkways and stairways, does this mean that we don't need to calculate it when preparing a calculation note for a storage tank ????
Thank you in advance
Of course you need to demonstrate that your design is adequate, in all aspects.
API is mostly concerned with the cylindrical tank. Structure other than the tank would need to follow other codes, OSHA, ASCE, AISC, good engineering judgment, etc.