120 110 100

which gives

The LRFD Specification [3] does not give a resistance factor for shear connectors, on the premise that the j-value of 0.85 for the overall design of the composite member incorporates the stud strength variability. This is not satisfactory for composite members such as stub girders and composite trusses. However, a study was carried out to determine the resistance factors for the two ultimate limit states for stud shear connectors [14]. Briefly, on the basis of extensive analyses of test data from a variety of sources, and using the Qn-equation as the nominal strength expression, the values of the resistance factors that apply to the shear yield and tension fracture limit states, respectively, are

Stud shear connector resistance factors:

Limit state of shear yielding: jconn = 0.90 Limit state of tension fracture: jconn = 0.75

The required number of shear connectors can now be found as follows, using the total stub shear forces, Ves and Vis, computed earlier in this section:

Exterior stub:

That is, use 14|-in. diameter stud shear connectors, placed in pairs and distributed uniformly along the length of the top flange of each of the exterior stubs. Interior stub:

That is, use 4|-in. diameter stud shear connectors, placed singly and distributed uniformly along the length of the top flange of each of the interior stubs.

Considering the shear forces for the stub girder of Figure 33.5 and Figure 33.7, the number of connectors for the exterior stub is approximately three times that for the interior one. Depending on span, loading, etc., there are instances when it will be difficult to fit the required number of studs on the exterior stub, since typical usage entails a double row, spaced as closely as permitted. Several avenues may be followed to remedy such a problem; the easiest one is most likely to use a higher strength concrete, as long as the limit state requirements for Qn and Table 33.1 are satisfied. This entails only minor reanalysis of the girder.

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