Figure 7.49b. Collector design forces.

1.74 kip-ft for the specified 3-inch-deep 20-gauge deck with a 31/4-inch lightweight concrete topping and puddle welds in every flute. See Table 7.9. Note that a one-third increase for seismic load is not permitted over and above the published values. Since the shear capacity of 1.74 kip-ft is greater than 1.67 kip-ft, the specified metal deck is OK for shear.

Drag-Strut (Collector) Design. Next we determine the drag-strut requirement by comparing the shear capacity of the metal deck with the calculated shear flow per ft length of frame given in row 6 of Table 7.8. The calculated values exceed the allowable capacity at grids A, B, and F. At these grids, drag struts must be designed to carry the shear in excess of the force transferred directly into the frames.

The two beams, each 20-ft long on each side of frames on grids A, B, and F, may be designed as drag struts. In addition to the gravity loads, these beams must be designed for the axial loads due to drag-strut action.

Table 7.8 Composite Deck Example: Collector Design
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