Info

where Ss is the section modulus of the steel beam, and V is the shear capacity provided by the shear connectors, obtained by multiplying the number of connectors used and the shear capacity of one connector. Transposing the above equation we get

reqd

AISC stipulates that V[ be not less than 0.25 V to prevent excessive slip and loss of beam stiffness. This minimum requirement does not apply if shear studs are used for reasons other than increasing the flexural capacity, such as for increasing beam stiffness or for diaphragm connectivity.

Figure 7.56. Shear connector requirements for composite beams subjected to concentrated loads: (a) schematic loading diagram; (b) shear connector requirements; (c) composite beam design example; (1) plan; (2) section.

The AISC specification gives three criteria for stud placement: 1) a minimum center-to-center spacing of six stud diameters between the studs in the longitudinal direction; 2) minimum spacing of four stud diameters in the transverse direction; and 3) maximum spacing in the longitudinal direction of 32 in. (813 mm). Note that if stud spacing exceeds 16 in. (406.4 mm), a plug weld between the studs is required to resist uplift forces.

If the required bending capacity is provided by the steel beam alone without relying on composite action, the maximum spacing requirement of 32 in. (813 mm) need not be met.

The recommended sequence for installing studs when the deck is perpendicular to the beam is as follows:

• Deck ribs at 6 in. (153 mm) on center. Start at beam ends and place a single stud at every fourth flute, working toward the center of beam. If studs remain, fill in empty ribs, again starting at beam ends and working toward the center without exceeding 30 in. (762 mm) for stud spacing.

• Deck ribs at 12 in. (305 mm) on center. Start at beam ends and place a single stud in every other flute working toward the center of beam. If studs remain, fill in empty ribs, again starting at beam ends and working toward the center of beam without exceeding 24 in. (610 mm) for stud spacing.

• If the number of studs is more than the number of ribs, place a double or triple row as needed, always starting from beam ends and working toward the beam center. In general, is studs cannot be uniformly spaced, the greatest number of studs should occur at the ends.

The recommended sequence for installing studs when the deck is parallel to the girder is as follows. Start at the girder ends by placing the first stud at approximately

12 in. (305 mm) from the centerline of support and work toward the center of girder with uniform spaces between the studs. If a double row of studs is required, it is a good practice to place them in a staggered pattern rather than side by side.

The allowable shear for stud connectors is influenced by several factors when used in metal deck construction. As in solid slabs, the strength and type of concrete, whether regular or lightweight, determines the allowable horizontal loads. The rib geometry of metal deck and the height of the stud above metal deck (when deck is parallel to the girder) are other factors influencing the allowable horizontal loads. For girders, the wider the rib opening and the greater the penetration of the stud above the deck, the more closely the allowable horizontal shear load will approach the published AISC value for studs in solid concrete slabs.

7.4.2.2. Design Example Given.

(W18 x 40), 50 ksi steel beam, beam span = 40 ft (Fig. 7.57) Beam sp10 ft

Tributary width for dead and live loads = 10 ft

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