Iv63:
Your latest design is an improvement in one respect and not so good in another. You have saved 6 miles of drilling, some probably through existing rebars, and gallons of epoxy. I trust that you will pour a new conc. wall, as tension rod cover, with some horiz. reinf’g. hoops. The thing I don’t like about your latest design is that you are trying to strengthen or take some of the tension loading from the tank column shell and existing A.B’s., which are very stiff attachments on very stiff chairs. But, the way you are doing this is through plate bending, with a varying canti. length to boot, a very flexible (soft) attachment means. This will not pick up as much load as you wish it would before the original A.B’s. start to overstress. They must stretch too much to make the plate flex enough to load the new tension rods, and then tension in the rods will still be very low. I trust that the tank column and the A.B. chairs are still o.k. with the new loads and A.B. tensions.
I think your new system wants to engage the old system right at the chairs where your design details can control the load out to the new tie rods. It appears that the existing A.B’s. and the corners of the octagonal pedestal are symmetrical w.r.t. each other. So, over a 45° arc, with a pedestal corner at the center of the arc, you might design 8 identical new chair systems which would fit over the existing chairs and maybe even under the existing A.B., and out to the new tie rods. Now, you can design this with varying stiffener (web) stiffness to account for the different canti. lengths out to the new tie rods. The top and bottom flange plates on this box section might stay the same. The existing A.B. pattern must be matched but the new tie rods will flex a bit to fit their hole pattern. Your new chair system would actually react on the outer edge of the new conc. wall, so your chair system clamps down on the old chairs. Then you might also vary the spacing of your new tie rods to optimize their action w.r.t. the varying canti. span lengths on your new chair system. Maybe these box beams should be 8 units for the long canti. spans, centered over the pedestal corners; and 8 units for the short canti. spans, each covering a 22.5° arc and engaging two existing A.B. chairs. Now you might vary the flanges and webs on these box beams and probably end up with something more easily fabed and welded (weld accessibility).
