I have built a larger version of Jack Sobon's Garden Toolshed which will be my workshop. It is 16' x 24' with a second floor loft. Four bents w/8x8 posts and 8x10 tie beam with mortised 4x4 bracing-all oak.

I am wondering if I will compromise the strength of the shouldered mortise if I cut a 3x3x4" joist pocket 10 to 12" from the tie beam joint. This would be the middle section-the first and third sections will have the joist pockets 2' on center.
The middle section joist pockets would be staggered between the 2' on center sections at 1',3',5' etc...I'm just wondering if I am getting to close to the joint.

I'm not qualified to give you an answer about this, but you could swap some head room and instead just place the floor joist on top of the beams instead of cutting pockets into them and possibly weakening them. I’ve seen this done in other structures, where they didn’t want to weaken the beam with pockets. Just a thought. Good luck with your project. Jim