How much weight will a pressure treated yellow pine beam 12 ft long carry at the center?

Answer 1

I don't think you will get too many answers for a question like this. It's just too ambiguous as it reads. What is meant by "carry weight"? Do you want to know the ultimate strength right before a beam breaks? What size beam? Or do you want to limit the term "carry" into meaning the amount of weight it can withstand before deflecting more than a usable amount.

If this is for a research/design situation, you should search for the terms wood beam deflection calculation. You should find some sites that will go through the calculations for you for several sizes of beams, materials, etc.

If you are just trying to build a deck or some other outdoor project, most home centers have plans that will spell out what is required for typical deck loadings. Generally, you can use those, but be sure to check for any local requirements that may dictate certain parameters of your construction.

Answer 2

You need to define a section at least. A 2 x 4 won't carry much, but a 8 x 20 is very beefy. Which is it? And is this a permanent load, a dead load, a live load, an impact load? And what type of end restraints, cantilevered, fixed, simple? Can the beam twist? What is the application? A hospital or a barn?