Problem 4 (25 points) Five planks are connected as shown by nails spaced (s) as shown in picture below along the longitudinal axis of the beam. For a vertical shear of 15 kN, determine the required spacing (s) if diameter of each nail is 4mm and the allowable shearing stress of nails is 500MPa. 20 mm 6 mm 6 mm 4 mm Frail = Cnail Anail - 2 = 500 MPa. (2) = 6283.18 N Frail = VQ. S I 3 Q = (4)(6)(7) = 168mm 3 I = (4)(20) + 4 12 (4716)+ (4)6(7) = 7658.8 mm 12 a) The maximum Compressive normal stress due bending b) The maximum Tensile normal stress due bending 3 in. 12 in. 3 in. 12 in. 3 in. comp. + 3 [(8)(3)(6)] = 3.61 in Y = (33)(2)(1) + (33)(2) + 3[(8)(3)] y - 2 in. 8 in. 33 in. Crop bottom tens. M M 3 I = (33)(2) + 12 3 (33)(2)(3.61-13)3 + 3 + (3)(8) (3)(8)(6 12 I = 1266.87 in" Problem points) A cross section shown in picture below Is under M=400 kip.ft. Angle of =60. Center of the shape is shown at C. Calculate: a) The normal stress at point D b) The normal stress at point B 2 in. By Mz 2 in. Mz M E C My D B 10 in. 2 in. 10 in. + + B how to input this on calculator I keep getting -380.96 for the 400cos(60) M = 400 kip. ft cos (60) = 200 kip. ft 400 kip. ft sin (60) = 346.4 Kip. ft 6 in. 2 in. 4 in. 2 in. 6 in. Dimensions in inches I = (20) (20) + 4 [(2)(10) Iz I = 12 3 (2)(20) 12 + 2 12 3 (10)(2) 12 My = = 3560 in (10)(2) (10)(2)(3) + 2 12 + = 4960