P Welded Connections for Tension Members

Figure 4.22 shows a tension angle member connected to a gusset plate by fillet welds. The applied tensile force P is assumed to act along the center of gravity of the angle. To avoid eccentricity, the lengths of the two fillet welds must be proportioned so that their resultant will act along the center of gravity of the angle. For example, if LRFD is used, the following equilibrium equations can be written:

Summing force along the axis of the angle:

Summing moment about the center of gravity of the angle:

where Pu is the factored axial force, fFM is the design strength of the welds as given in Table 4.18, teff is the effective throat thickness, L1, L2 are the lengths of the welds, and d1, d2 are the transverse distances from the center of gravity of the angle to the welds. The two equations can be used to solve for L1 and L2. Welded Bracket-Type Connections

A typical welded bracket connection is shown in Figure 4.23. Because the load is eccentric with respect to the center of gravity of the weld group, the connection is subjected to both moment and shear. The welds must be designed to resist the combined effect of direct shear for the applied load and any additional shear from the induced moment. The design of a welded bracket connection is facilitated by the use of design tables in the AISC-ASD and AISC-LRFD Manuals. In both ASD and LRFD, the load capacity for the connection is given by

where P is the allowable load (in ASD), or factored load, Pu (in LRFD), kip; l is the length of the vertical weld, in.; D is the number of sixteenths of an inch in fillet weld size; C are the coefficients tabulated in the AISC-ASD and AISC-LRFD Manuals. In the tables, values of C for a variety of weld geometries and dimensions are given; C1 are the coefficients for the electrode used (see following table).


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