Question

Check the adequacy of a W18X35 for a beam (the beam in the vertical direction in the plan) in a floor framing system in terms of 1) bending strength; 2) shear strength and 3) deflection. The beams support a 4-inch-thick reinforced concreted floor slab (with a density of 150 lbs/ft?). Besides the weight of the structure, loads consist of a uniform live load of 80 psf and moveable partitions (with a uniformly distributed load of 20 psf of floor surface). The maximum live load deflection must not exceed 1/360 of the span length. Use A992 steel. Assume that the slab provides continuous lateral support of the floor beams. Use LRFD. The beam to be checked in this question. 30' 0 I I T 67'-0" 42'-0"

Answer 1

ANSWER :
Here i Given that: Thickness of Hoov = 4" Self weight of floor = (1/12)x150 = 50 pof live load =80 pot paste tion load - 20pst Total live load = 80+20 = 100 pot span of beam = L = 30' Tributary width of beam = 0.5x spacing of beam to right +0.5x spacing of beam to left = 0.5X770587=1'." Total uniform Dead load on beam – dead load from Hoor + beam self weight = (50x7)485 385 lblift = 0.385 kiplft Total live load on beame 100x7 = 700 &blft = 0.7 kpplft per LRFD load.com bination of 1.20+ 162, Design load on beam - we = 1-2x0.995 + 1 - 6X0-7 = 1.582 kpplft Design moment in beam = mer Wux 178 = (582x 30 = 128 kipoft 8

a 2 Maximum Shear force in beam = Nu Ewx L 1.582 x 30 = 23.7 Kipsi Since the beam as continuously braced, moment capacity of beam is equal to plastic moment capacity per Table 3-2 of AlSC 360 -10, plastic moment capacity of W18x35 = 249 kip-ft shear strength of W18x35 z 159 kips. . beam 95 adequate in berdeng strength and shear Strength Deflection check. Total love load on beam = We = 0.1 kplht = 0.0583 kiplin Moment of inentia of section = 1 510 804 span of beam = L = 30' 2.360in modules of elasticity Beflection of simply supported beam due to uniform (5/384)x wil x 24/CEx ;) - € = 29000 ksi load =

X0-0583 x 3604/129000X510). 384 0.86in Allowable deflection. 2 360 360 360 section is adequate in deflection strength as well as