how did you connect the 8' sections together?

Each section consisted of a 2x6 pressure treated sole plate, a 2x6 top
plate, and seven 2x6 studs (16" OC). This framework was then covered with
two sheets of 1/2" rough sawn plywood (like T-111 without the grooves),
nailed every 6" around the edges and every 12" in the middle. The studs
were cut at 90.5" so the plywood could overlap the foundation an inch, and
accomodate a double top plate. (It helps to use a scrap 2x6 as a gauge for
the second top plate when nailing on the plywood. This leaves 1-1/2"
sticking above the wall to overlap the second top plate when it is
installed.)

We would build the section, tilt it up onto the foundation, use small
sledge hammers, crowbars, clamps, etc. to get it aligned and pull it tight
against the previous panel. We then tightened the anchor bolts to pull the
section down level with the previous section, and nailed the two panels
together.

Sometimes the panels go up easy, sometimes it takes a bit of "persuasion"
to make them fit tightly. On a couple of occasions, this meant loosening
the anchor bolt on the previous panel, and prying it up slightly to align
the two panels. Then they were nailed together, and the anchor bolts
retightened. Thankfully, most panels went up without any problems.

Once the panels are in place, a second top plate overlaps the gaps between
panels, effectively tying them all together. I then nailed the top of the
siding to the second top plate all along the top of the wall. When all
walls were finished, I went around and snugged up the anchor bolts (not so
much as to compress and damage the wood though).

does this cause any structural strength loss at all?

If anything, it should make it stronger. In effect, you are making a post
(doubled 2x6) every 8 feet where the panels join. And, every sheet of
plywood bears on a full stud on one side, which offers more support than
two sheets landing over a single stud. And, once the second top plate goes
on, it's all tied together into a single wall anyway.

The only real negative is that you end up using an extra stud every 8'. But
in a 24'x28' garage, that's only about 10-15 extra studs. Small cost in the
overall project.

Also, I used plywood with a "shiplap" edge. This meant paying attention to
which edge went over and which went under as I assembled the panels. I made
sure each new panel would overlap the previous panel. This sealed the gap
between sections, and was easier to align than trying to force the new
section under the overlap of the previous panel.

Because of the long headers in the front wall, I built the front wall in
place. I assembled the small wall sections on the floor, then bolted them
to the foundation. The door headers were then installed, and everything was
plumbed and braced. THEN I nailed the plywood siding on, and cut out the
door openings. Because of the size and weight of the headers, it would have
been difficult to try building these as panels and lifting them into place.
By temporarily screwing 2x6 blocks to the top edge of the plywood (where
the second top plate would go), I could basically "hang" the sheet on the
wall and have it support itself while I nailed it in place.

Once the front wall was done, I built two short 4' panels for each of the
side walls. This helped brace the front wall, and made up the difference in
the 28' side walls (28' doesn't divide evenly by 8'). Then the rest of the
garage was built with 8' panels.

Take your time, work slowly, and plan through what you're gonna do before
you do each step. The only time I really had problems is when I would get
in a rush. Also, mistakes happen, expect it. Think it through, take things
apart if needed, and do it right. It'll seem difficult at first, but you'll
be a pro by the time you finish the building...

Anthony