Hi everyone, I have recently been tasked to find the stress, strains as well as safety factors for a human sitting on a folding stool. While I have prior knowledge of stress and strain calculations, I am quite clueless on how I should go about starting my calculations for this particular item. I have attached an image of the chair below. It can be assumed that the chair is just a cuboid, and that the faces at the side is a full rectangle unlike the one shown below where there are some material cut off to reduce the weight. The material it is made of is HDPE. I would really appreciate any help or hints for me to get started!

Well, first you need to know, or make some assumptions, about how and where the person's weight is distributed across the top plate. Given the relative softness of the HDPE material, it will be statically indeterminate to a large extent, unless you make some very rough simplifying assumptions.

Thank you very much for your input Dana. Based on what I have learnt thus far, I realized that the relevant topics were only covered in a 2D sort of space, beam bending etc. Thus I was unclear on how to go about doing calculations for this since it is there are multiple points of support in a 3D space. I would be very glad to take input of any sorts, thus for these assumptions that you were mentioning, what would be your recommendation for them? Thank you