Question

2. The composite beam cross section shown below consists of a W16 x 45 steel with ASTM A572 grade 50 and 4in. normal weight (145 pef) concrete slab, with 28-day strength of 3ksi. Assume full-composite action. Consider only the loads shown in the figure. b = 66 Service Leads Construction Dead Load: 0.75 k. Superimposed Dead Load: 0.25 kft. Live Load-1.1 kft. -W16 X 45 L-36-0 a) Determine the design bending strength in k-ft of the composite section using formula. Compare results with the AISC manual tables. Is the section adequate for bending? b) Determine lle from AISC Table 3-20. Is the section adequate for post-composite deflections (compare with L/480)? c) Determine the number of 3/4" studs required for the entire beam. Assume one stud is in deck ribs in the strong direction.

Answer 1

ANSWER :

Given that :
composite action exists between the concrete slab. and the metal deck. The effective flange width of beam beft is. equal to 66 inches e includes the slab portion also ). The depth at of the I section is 16.13 inches. Compressive of concrete fit 3ksi deptht of concrete slab is a inches. The metal deck rits height hy is of 2 Ponch thickners Diameter of headed studs is 0.75 inch fy = 50ksi. t = 0.565 inches (thickness of flange of met es (thickness of flange of metal deckplate ) Thickness of web.plate is 0.345 inches width of the Hange of metal deck bis 7,035 Inces. controlling compression borce by concrete Ny Ps 0.85€ 'beyxt equal to 0.85 x 3x66X4 which is. 673. 2 kips. Area of I shaped W Section Ag = 13.3in2 Steel canying tension borce Nis is hy this = 50x18.310 = 665 kips

full composite ac lion exists between steel and concrete Shear connectors must carry the smaller walewo of ve', and vq = 665 kips. The tension force created by steel Pg lesser than the compression force created in the concrete plastic Neestral avis (PNA) B.90 the concrete zone. The depth of the neutral axis a is ty As oogste beft which is 665kpps & 29612 inches. 0185x3x66 And the nominal moment strength Mousing formular Mn = Tsx ( 2 / J2 [t the 2] = 665x ( 16 13 2 660 (6 - 3.9012 . 803945 in kips. 2 669.95 ft-kips. an service live load Pg plklft. (B) length of th beam = 36 ft.

value of 42 25 4 _ 3.9512 2.0244in. value of I LB = 690 ing DL= 5X11X364x 1728 384 X29000x 690 = 2.07 en 70.990 section is inadequate for live load deflection diameter of the single stud ig 0.75 inch- Normal wt concrete is used. compressive stress of concrete, t' = 3 ksi. Refer table "Nominal shear strength for one stud" strength of one single stud an is 21 kips. Average width of the rib, w is 6. 125 inches- the ratio of width to ht of the ribs is equal to Way which ag 6: 125 -3.0625 ? than 1.5 Adjustment factors table Refer shear stud strength Deck ribs are perpendicular to sted beam, with one stud-

Ps in same decking rob has multiplier factor Rq = 1 the multiplier Rp accounts for the location of stud in the ribs - Rp = 0.6. the strength of stud based on the placement and arrangement is Rg Rp Asv fu equal to kk OnGX Tx BT5 465 = 17.23 kips The stud strength is of lower among the two 17.23 kips. Number of headed studs. required for full composite action is 665 = 88.60 17.23 Give 39 headed studs for one half of span, Use 78 headed studs for the entire beam,