A floor system consisting of wooden joists spaced 6 ft apart on the center and a tongue and groove wood boarding, as shown in Figure , supports a dead load (including the weight of the beam and boarding) of 20 psf and a live load of 30 psf. Determine the maximum factored load in lb/ft that each floor joist must support using the LRFD load combinations.

 A floor system consisting of wooden joists spaced 6 ft apart on the center and a tongue and groove wood boarding, as shown in Figure , supports a dead load (including the weight of the beam and boarding) of 20 psf and a live load of 30 psf. Determine the maximum factored load in lb/ft that each floor joist must support using the LRFD load combinations.

Solution

Dead load D = (6)(20) = 120 lb/ft

Live load L = (6)(30) = 180 lb/ft

Determining the maximum factored loads Wu using the LRFD load combinations and neglecting the terms that have no values, yields the following:

Wu = (1.4)(120) = 168 lb/ft

Wu = (1.2)(120) + (1.6)(180) = 288 lb/ft

Wu = (1.2)(120) + (0.5)(180) = 234 lb/ft

Wu = (1.2)(120) + (0.5)(180) = 234 lb/ft

Wu = (1.2)(120) + (0.5)(180) = 234 lb/ft

Wu = (0.9)(120) = 108 lb/ft