Engineering is difficult to do over usenet, but here are some general
comments.


"Dan Oelke" wrote in message
...

In my current abode they used floor trusses for both the first and
second floor. From the basement I have easy access (for now) to the
first floor trusses. They are great in that they allow for such a long
span and a very open floor plan. However - there is a fair amount of
bounce in the floors, especially when two kids get a little excited
running around the house. This is especially true in the kitchen area
which has cabinets all around, heavy appliances, island, etc. so I
suspect that this added "normal" load makes them a little more flexible.

Does anyone have any suggestions for how to stiffen or strengthen these
trusses? There is currently one strongback going across the trusses
about mid-span between the supported ends. This isn't something that I
am afraid has been under-engineered to start with. From my reading of
some span tables, etc the spans are well within what they can be for
that size of truss. I'm just looking to reduce the rattling of
glasses/light fixtures, etc when the kids go jumping.

Some ideas I have had a

1) Add additional strongbacks. How big is useful? Would a 2x6 do much
or do I need a 2x10 or 2x12 before it does any good? Going around
heating ducts and drain lines could prove somewhat a challenge to get
bigger sized material in place.

All this does is spread the load over adjoining trusses. What you have their
already is probably doing most of the work. Not the biggest bang for the
buck.


2) Put in some kinds of cross-bracing between the trusses - like you
normally see for normal joists. Allows for easier maneuvering around
utilities. This of course begs the question - wood or metal.

Again, just spreads the load a bit, but doesn't add much in the way of
strength.


3) Add plywood gussets on the truss sides where I can. Because of
heating ducts, plumbing, etc, there are some places that I couldn't, but
most places I could. Does it help/hurt to only do this on one side? Do
the extra fasteners into the 2x4's hurt their strength?

Slapping 1/2 plywood on both sides would stiffen things up immensely. One
side would probably be OK. The amount of eccentricity created is fairly
minimal. I'd probably use glue and nail every 6 inches or so. The strength
of the plywood should more than make up for any issues created by nailing


4) Do some/any of the above after jacking up the center of the truss by
a small amount (1/4" ??) so that the re-enforcing is taking the load
right away.

If your floor is deflected without load and you want to fix it, then do
this. Otherwise there is not much need.

Any other brainstorms?

You could double up the bottom chord. This will help somewhat if it is well
attached.

-j