User guide

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.