Page 83 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch03.qxd 9/29/05 5:05 PM Page 3.15

CONNECTIONS

CONNECTIONS 3.15

hole to an edge of a connected part should not be less than the applicable value from Table 3.2 unless
smaller distances are justified by analysis (see footnote a of Table 3.2). Note that Table 3.2 gives edge
distances from the center of a standard hole to the edge. This is denoted L e in the following.
Edge-distance strength limitations for bolted connections are given in the AISC Specification
in terms of clear distance L c , which is related to L e by

L = L + d h (3.9)
e c
2
where d h is the hole diameter. For standard holes, oversized holes, short slotted holes regard-
less of the direction of the loading, and long slotted holes with the load perpendicular to the slot, the
nominal strengths are as follows:
When hole deformation is a design consideration:
R = 12 L tF ≤ 24 dtF u (3.10)
.
.
n
c
u
When hole deformation is not a design consideration:
.
R = 15 L tF ≤ 30 dtF u (3.11)
.
n
c
u
For long slotted holes with the load parallel to the slot, the nominal strength is
.
R = 10 L tF ≤ 20 dtF u (3.12)
.
n
c
u
where F u = minimum specified tensile strength
d = bolt diameter
t = thickness of critical connected part
Maximum edge distances are set for sealing and stitch purposes. The AISC Specification limits
the distance from center of fastener to nearest edge of parts in contact to 12 times the thickness of
the connected part, with a maximum of 6 in. For unpainted weathering steel, the maximum is 5 in or
eight times the thickness of the thinnest outside plate.
3.2.4 Requirements for Fillers
A filler is a plate inserted in a splice between a gusset or splice plate and load-carrying members to
fill a gap between them, such as results from differences in section depth. Requirements for fillers
included in the AISC Specification for structural steel for buildings are as follows.
1
In welded construction, a filler / 4 in or more thick should extend beyond the edge of the splice
plate and be welded to the part on which it is fitted (Fig. 3.10). The welds should be able to transmit
the splice-plate stress, applied at the surface of the filler, as an eccentric load. The welds that join the
splice plate to the filler should be able to transmit the splice-plate stress and should have sufficient
1
length to prevent overstress of the filler along the toe of the welds. A filler less than / 4 in thick should
have edges flush with the splice-plate edges. The size of the welds should equal the sum of the filler
thickness and the weld size necessary to resist the splice-plate stress.
In bearing connections with bolts carrying computed stress passing through fillers thicker than
1 / 4 in, the fillers should extend beyond the splice plate (Fig. 3.11). The filler extension should be
secured by sufficient bolts to distribute the load on the member uniformly over the combined cross
section of the member and filler. Alternatively, an equivalent number of bolts should be included
3
1
in the connection. Fillers / 4 to / 4 in thick need not be extended if the allowable shear stress in the
bolts is reduced by the factor 0.4(t − 0.25), where t is the total thickness of the fillers but not more
3
than / 4 in.
Fillers in slip-critical connections need not be developed by the addition of extra bolts when pre-
vention of slip is required for strength rather than serviceability.

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