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Steel Designers' Manual - 6th Edition (2003)
938 Tolerances
Holding-down bolts and other fixing bolts are either:
(1) fixed in position, or
(2) adjustable, in sleeves or pockets.
31.5.3.2 Fixed bolts
Fixed bolts used to be solidly cast in, an operation requiring care and the use of jigs
or templates to achieve accurately. However, they are now also commonly produced
by placing resin-grouted bolts in holes drilled in the concrete after casting. It may
also be possible to use expanding bolts.
In whatever way fixed bolts are achieved, they need to be positioned accurately,
as the only adjustment possible is in the steelwork, so relatively close tolerances are
normally specified.
31.5.3.3 Adjustable bolts
Adjustable bolts are placed in tubes or in tapered trapezoidal or conical holes cast
in the concrete, so that a degree of movement of the threaded end of the bolt is possible,
while the other end is held in place by a steel washer or other anchoring device
embedded in the concrete.
This alternative permits the use of more easily achieved tolerances for the bolts,
while using relatively simple details for the steelwork.Adjustment of the bolt necessitates
its axis deviating from the vertical to some extent, and the holes in the steelwork
need to be large enough to allow for this, particularly if the baseplate is thick.
The use of loose plate washers is recommended to span oversize holes if necessary.
If required they can be welded in place after the bolts are tightened, but this should
not normally be necessary. ‘Particular’ tolerances need to be worked out for each
case, depending on the details, including the length of the bolts, because this affects
their slope.
31.5.3.4 Length of bolts
The level of the top of an HD bolt is also important to ensure that the nuts can be
fitted properly after erection. To provide the necessary tolerances for the fixing of
the bolts they should be longer than theoretically required, long threaded lengths
should be provided, and the nominal level for the top should be above the theoretical
position.
Similar considerations apply to the lengths of fixing bolts located horizontally.