Steel plate to be welded onto top chord of existing roof truss One Steel Plate Two Equal Leg Angles Back to Back Figure 1: Existing Roof Truss Section Figure 2: Proposed modification Case No. Equal Double Angles & Plate L-Shape Plate Size 3 L5x5x12 8" x 1" DOUBLE ANGLES Two equal leg angles Properties of sections Wt. Area AXIS X-X AXIS Y-Y per Ft of Radii of Gyration Angles Angles Designation 2 2 Angles Angles Sy Back to Back of in Contact Separated Angles, In. 997 935 2.50 2.19 3.32 3.45 3.58 995 921 911 834 Lb. In 2 In. In. In. In 0 % % 36 ksi 50 ks 36 ksi 50 ks L 8x8x1% 1 % % % ½ 113.8 33.5 195.0 102.0 30.0 177.0 31.6 90.0 26.5 159.0 28.0 77.8 22.9 139.0 24.4 65.4 19.2 118.0 52.8 15.5 97.3 35.1 2.42 2.41 3.42 3.55 3.69 2.44 2.37 3.40 3.53 3.67 2.45 2.32 3.38 3.51 3.64 20.6 16.7 2.47 2.28 3.36 3.49 3.62 2.49 2.23 3.34 3.47 3.60 118 L 6x6x1 74.8 22.0 70.9 17.1 % 66.2 19.5 63.8 15.3 % 57.4 16.9 56.3 13.3 % 48.4 14.2 48.3 11.3 ½ 39.2 11.5 39.8 % 29.8 8.72 30.8 811111 L 5x5x % 81111 8111 982 919 81111 111 | 11 ||||| .961 ***** 54.4 16.0 35.5 47.2 13.9 31.5 32.4 9.50 22.5 24.6 7.22 17.5 20.6 6.05 14.8 15.3 31.4 9.22 13.3 25.6 7.50 11.1 19.6 5.72 L 4x4x % % ****** 37.0 10.9 % 16.4 4.80 1.80 1.86 2.59 2.73 2.87 1.81 1.82 2.57 2.70 2.85 1.83 1.78 2.55 2.68 2.82 1.84 1.73 2.53 2.66 2.80 9.23 1.86 1.68 2.51 2.64 2.78 7.06 1.88 1.64 2.49 2.62 2.75 995 921 911 834 10.3 1.49 1.57 2.16 2.30 2.45 9.06 1.51 1.52 2.14 2.28 2.42 6.31 1.54 1.43 2.10 4.84 1.56 1.39 2.09 2.24 2.38 2.22 2.35 4.08 1.57 1.37 2.08 2.21 2.34 995 921 911 834 5.62 1.19 1.27 1.74 1.88 2.03 4.80 1.20 1.23 1.72 1.86 2.00 3.95 1.22 1.18 1.70 1.83 1.98 8.72 3.05 1.23 1.14 1.68 1.81 1.95 7.43 2.58 1.24 1.12 1.67 1.80 1.94 111118 1111 211111 1111 997 935 13.2 3.88 6.08 2.09 1.25 1.09 1.66 1.79 1.93 995 921 911 834 Where no value of Q, is shown, the angles comply with the noncompact section criteria of Specifica- tion Sect. B5.1 and may be considered fully effective. For Fy 36 ksi: C 126.1/V - For F, 50 ksi: C-107.00, AMERICAN INSTITUTE OF STEEL CONSTRUCTION Purpose: Directions: The Home DepotⓇ in Red Hook, Brooklyn is looking to renovate their steel roof truss (Figure 1). They are considering welding a steel plate to the top chord of the truss to improve its strength (Figure 2). You are a staff engineer at a local engineering firm. You have been asked to determine the centroid, moment of inertia, section modulus and radius of gyration of the double angle and plate connection. Your supervisor told you which case to analyze. Calculations: 1. Sketch the shape to scale using the dimensions from your case number. No Calculations on this page, please. Double angle property dimensions are given in the file "AISC Shape Properties." 2. Please select the bottom centerof the given cross-section as an origin of your reference axis. Then calculate: a. Location of the centroid, (x, y) b. Moments of Inertia, Ix(in) c. Radius of Gyration, rx(in)