Page 156 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

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CONNECTIONS

3.88 CHAPTER THREE

β
3.7.3 Satisfying Geometric Constraints and α
Another problem arises when the geometry will not allow either α or β to be located as pre-
scribed by the uniform force method. In such cases it is logical to assume that the more rigid con-
nection takes all of the moment necessary to satisfy equilibrium. For instance, where the gusset
α
β
plate is welded to the beam and bolted to the column, should be assumed equal to β and should,
if necessary, be unequal to α so that all the moment is distributed to the more rigid beam-to-gusset
connection.
The AISC Manual introduces two new equations to handle these situations, M b = V b (α − α) and
β
M c = H c ( −β). However, the equations for M g , M b , and M c already presented will work equally well. If
β ≠β then M c will act at the gusset-to-column interface. If α ≠α, then M b will act at the gusset-to-
column interface. One exception is when ∆V b is introduced and β ≠β. In this case, as shown earlier,
∆V b will cause an internal moment in the column. The result from the M c equation will then reflect the
total moment both internal and external to the column. The moment that exists at the gusset-to-column
interface can be calculated as

(3.73)
M c−interface = M g − M b

FIGURE 3.50 Example of bracing connection design. (Source: A. R. Tamboli, Handbook of
Structural Steel Connection Design and Details, McGraw-Hill, 1999, with permission.)

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