0770

Because a' > 1, use a' = 1 to calculate the design strength, fT.

4>T = (f>B (-1 (1 + Sa') = 40.6 ((1.69) = 25.6 kips > 22.4 kips

Bolts and bracket flange are OK for bending and prying action.

Check web of W18 X 86 bracket for limit state of shear on gross section:

fRgv = fs0.60FyAg = 0.90 X 0.60 X 50 X 0.480 X 21 = 272 kips > 115 kips, OK.

Check flange of W18 X 86 bracket for limit state of shear on net section:

4>Rnv = fs0.60FuAn = 0.75 X 0.60 X 65 X 0.770 X (21

Check web of W18 X 86 bracket for bending limit state:

Check flange of W18 X 86 bracket for bearing limit state:

For the column flange, a similar check shows that bearing is OK. Bending in the column flange must also be considered. In this case, the A572-50 column flange is assumed to be 0.770 in. or thicker, and therefore, is considered OK without calculations. See Art. 5.36 for applicable method for thinner flanges where calculations are required.

Finally, the stability of the column web should be considered. First, if the loading conditions are such that the load can move out of the plane of the bracket web, a top stiffener plate should be used to prevent such motion. Then use the procedure of Salmon and Johnson to assess the web stability under the compressive stresses. In some cases, if the web is too slender, a thicker web or an edge stiffener may be required. (C. G. Salmon and J. E. Johnson, Steel Structure—Design and Behavior, Harper Collins, New York.)

Welds in Tension and Shear. Brackets also can be connected to supports with fillet welds in combined shear and tension. For the bracket in Fig. 5.49, for example, the welds carry a shear (kips per in) of where P = load on bracket, kips

L = total length of welds, in

In addition, the moment is resisted by the upper portion of the welds in tension and the pressure of the lower part of the bracket against the support. Both the elastic and inelastic methods assume that the weld carries all the load (bearing pressure between the bracket and the lower part of the support is neglected). The neutral axis is taken at the center of gravity of the weld group. The intensity of load at any point in the weld is proportional to the distance from the neutral axis, and the resisting moment per inch is proportional to that distance. For the elastic method, tension (kips per in) at the most heavily stressed point of the welds may be computed from where M = moment on weld groups, in-kips

S = section modulus of weld group about its neutral axis, in3

Example—Brackets with Welds in Tension and Shear—AISC LRFD. An A36 steel plate bracket is to be connected with fillet welds on two sides of the plate to a building column (Fig. 5.49). The bracket carries a 115-kip factored load 14 in from the column flange. The welds are to be made with E70XX electrodes.

FIGURE 5.49 Bracket with welds in combined shear and tension.

FIGURE 5.49 Bracket with welds in combined shear and tension.

Elastic Method. Assume a plate V2 in thick. With design stress of 0.90 X 36 = 32.4 ksi, the length of plate at the support should be at least

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