Light grade steel channel was used as purlin of the truss. The top chord of the truss is inclined 1V:3H and the distance between the trusses is 5m. The purlin weighs 100n/m and spaced at 1m apart. The roof carries superimposed dead load of 1000 Pa (including its weight) and the ceiling carries a load of 1200 Pa. Roof live load is assumed to be 1500 Pa. The roof is part of the building located at a place where the design wind speed is 240 kph. Assume the unit weight of air to be 12 N/m3. The windward coefficient is 0.20 and the leeward coefficient is 0.70. For this problem, assume that the allowable bending stress of beam is 60% and 75% of its yield strength in the strong and weak axis respectively. Assume all loads passes through the centroid of the section. Properties of C 250x85 ; Sx= 122 x103 mm3 ; Sy= 49 x103 mm3; Fy=300 MPa; Fbx (Allow. Bending Stress)=0.6Fy;Fby (Allow. Bending Stress)=0.75Fy What is the ratio of the actual to allowable bending stress for load combination 0.75(D+L+W) if sag rod is placed at midspan?
PROBLEM: Light grade steel channel was used as purlin of the truss. The top chord of the truss is inclined 1V:3H and the distance between the trusses is 5m. The purlin weighs 100n/m and spaced at 1m apart. The roof carries superimposed dead load of 1000 Pa (including its weight) and the ceiling carries a load of 1200 Pa. Roof live load is assumed to be 1500 Pa. The roof is part of the building located at a place where the design wind speed is 240 kph. Assume the unit weight of air to be 12 N/m3. The windward coefficient is 0.20 and the leeward coefficient is 0.70. For this problem, assume that the allowable bending stress of beam is 60% and 75% of its yield strength in the strong and weak axis respectively. Assume all loads passes through the centroid of the section. Properties of C 250x85 ; Sx= 122 x103 mm3 ; Sy= 49 x103 mm3; Fy=300 MPa; Fbx (Allow. Bending Stress)=0.6Fy;Fby (Allow. Bending Stress)=0.75Fy
What is the ratio of the actual to allowable bending stress for load combination 0.75(D+L+W) if sag rod is placed at midspan?
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