http://www.costco.com/Browse/Product...=1&topnav=&s=1

I'm in the process of installing pergolas like this except 10' x 12' and in
aluminum construction. I have a little problem in tying the steel base to
the concrete slab as the manufacture only make provision for anchoring in
dirt with four 12" long spikes for each base. Further the four holes in each
base where the spikes goes are higher than my longest concrete screws could
reach. I could cut and weld the base and provide brackets for the concrete
screws - more work than I want to get into which could easily be done at the
factory. There are no provision for leveling the bases so I need establish
the highest point and adjust the height for the other three bases
individually since the concrete slab is slopped for drainage. Once the base
is solidly tied down the whole free standing structure could be moved to
sway back and forth laterally with just one finger - there are no cross
beams or stiffening support. Should be enough for strong winds just don't
like the idea that is will sway that much. Anyone installed one of this and
how did you tie the base to the concrete slab?