Mueller Pre-Fab - Manual (Page 28)

877-2-MUELLER C-8
RaIsInG RIGID fRaMes (conTInUeD)
When the rafters consist of several roof beams, as in the case of wide buildings, a safe procedure
of raising by sections and supporting the free end must be followed, regardless of the type of
equipment available . In most instances the work proceeds from outside columns inward toward
the peak until the entire frame is bolted into place .
The same general procedures of erection apply to either clear span or multiple span frames . In the
case of the latter, the support for rafter sections during erection is generally supplied by the interior
columns themselves, making temporary supports unnecessary .
Two words of caution concerning the erection of rigid frames are in order . The first is that rigid
frames, especially free ends or cantilevered sections should never be left “for the day” in an
unsupported, unbraced or unguyed condition . Such practice has resulted in the total loss of
considerable amounts of erected steel because of wind . The second word of caution pertains to
the additional care required in the erection of multiple span frames compared to clear span frames .
Frames with interior columns, because of closer supports, have much lighter sections . They are
much more apt to buckle during erection than clear span frames, and consequently require greater
care in rigging and handling .
connection bolts
Bolts used to make connections in secondary framing members such as the purlins are usually
1/2” diameter, ASTM designation A307 . All primary framing or main framing connections are
made with ASTM A325 bolts, usually 5/8”, 3/4”, 7/8” and 1” diameters . The size and grade of the
bolt are marked on the building erection drawings .
MaIn fRaMe: an assemblage of rafters and columns that support the secondary
framing members and transfer loads directly to the foundation.
seconDaRY fRaMInG: Members that carry loads from the building
surface to the main framing. for example – purlins and girts.