The attached sketch shows the Roof Framing Plan of a Proposed Commercial Building with a DEAD LOAD of 60 psf and a LIVE LOAD of 120 psf
1. Assuming that the compression flanges of Roof Beams RB1 and RB2 have full lateral support:
a) Select the least-weight wide flange member for Roof Beam RBI (assume self-weight of 30 p11). Check Live Load Deflection. (4 points) b) Select the least-weight wide flange member for Roof Beam RB2 (assume self-weight of 40 pit). Check Live Load Deflection. (4 points) Note: Live Load Deflection shall not exceed 1/360 of Span Length
2. a) Determine the Maximum Moment (Mmax) and Maximum Shear Force (Vmax) acting on Roof Girder RG3 (2 points)
b) Assuming that the compression flange of Roof Girder RG3 is laterally supported at the supports and at 10ft intervals only (Lb =10ft) determine if a proposed W24x68 section is adequate to carry the loads acting on RG3
i) Determine Allowable Moment from the Lateral —Torsional Buckling Equation Mn/fib = Cb (Mp/S2b — BF/Sh(Lb-Lp)) (7 points) where Cb=1 .0
Select values of Mp/flb , BF/ 2b, 1,, from AISC Steel Construction Manual Table 3-2
(ii) Determine Allowable Shear Force (3 points) Select value of Vn/f2v from AISC Steel Construction Manual Table 3-2 and compare with maximum applied Shear Force
Assume Minimum Yield Strength of Steel is 50 ksi Safety Factor for Bending Gb = 1.67 Safety Factor against Shear Failure tin = 1.50