- Compute the unit force in the shop weld
The shop weld connects the angles to the beam web. Refer to Sec. 1 for two calculation
procedures for analyzing welded connections.
The weld for one angle is shown in Fig. Ib. The allowable force, as given in Sec. 1, is
m = 2(2.5)(1.25)/[2(2.5) + 12] = 0.37 in (9.4 mm); P = 20,000 Ib (88.9 KN); M= 20,000(3
- 0.37) = 52,600 in-lb (5942.7 N-m); Ix = (!/i2)(12)^3 + 2(2.5)(6)^2 = 324 in^3 (5309.4 cm^3 ); Iy
= 12(0.37)^2 + 2(Vi2)(2.5)^3 + 2(2.5)(0.88)^2 = 8 in^3 (131.1 cm^3 ); J= 324 + 8 = 332 in^3
(5440.5 cm^3 ); fx = MyIJ = 52,600(6)7332 = 951 Ib/lin in (166.5 N/mm); fy = MxIJ =
52,600(2.5)(0.37)/332 = 337 Ib/lin in (59.0 N/mm); fy = 20,0007(2 x 2.5 + 12) = 1176
Ib/lin in (205.9 N/mm); Fx = 951 Ib/lin in (166.5 N/mm); Fy = 337 + 1176 = 1513 Ib/lin in
(265.0 N/mm); F= (951^2 + 15132 )^05 = 1787 < 1800, which is acceptable.
- Compute the shearing stress in the web
The allowable stress given in the AISC Manual is 14,500 lb/in^2 (99.9 MPa). The two an-
gles transmit a unit shearing force of 3574 Ib/lin in (0.64 kN/mm) to the web. The shear-
ing stress is v = 3574/0.403 = 8870 lb/in^2 (61.1 MPa), which is acceptable.
- Compute the unit force in the field weld
The field weld connects the angles to the supporting member. As a result of the 3-in
(76.2-mm) eccentricity on the outstanding legs, the angles tend to rotate about a neutral
axis located near the top, bearing against the beam web above this axis and pulling away
from the web below this axis. Assume that the distance from the top of the angle to the
neutral axis is one-sixth of the length of the angle. The resultant forces are shown in Fig.
Ic. Then a = (V 6 ) 12 = 10 in (254 mm); b = (^2 / 3 )12 = 8 in (203 mm); B = 20,000(3)/8 =
7500 Ib (33.4 KN);£ = 2RIa = 1500 Ib/lin in (262.7 N/mm);/; = 20,000/12 = 1667 Ib/lin
in (291.9 N/mm); F (1500^2 + 16672 )^0 5 = 2240 < 2400 Ib/lin in (420.3 N/mm), which is
acceptable. The weld is returned a distance of (H in (12.7 mm) across the top of the angle,
as shown in the AISC Manual.
DESIGN OFA WELDED SEATED
BEAM CONNECTION
A W27 x 94 beam with a reaction of 77 kips (342.5 KN) is to be supported on a seat. De-
sign a welded connection, using E60 electrodes.
FIGURE 7. Welded flexible beam connection.
