Here's how engineers thinking about welding joints: https://www.youtube.com/watch?v=SZiEoN8tYvI https://www.youtube.com/watch?v=SZiEoN8tYvI You'll note in thos

Here's how engineers thinking about welding joints: https://www.youtube.com/watch?v=SZiEoN8tYvI https://www.youtube.com/watch?v=SZiEoN8tYvI You'll note in those calculations that he assumes that the weld is basically the same as the base metal. As long as the weld is performed properly, the assumptions should hold to within a factor of safety. For the relatively thin material used in cars and motorcycles, it doesn't take very long for the metal to melt all the way through in a single spot, so very strong welds can be created quickly. Further, between the skill of the fabricators and editing for TV, it is hard for someone without familiarity with welding to know what all is going into a joint just by watching the footage after. Do you have a specific show in mind?