Question

Refer to the plan view below for a partial roof framing plan of a building (note that this is not to scale, use dimensions indicated). A slope of inch per foot is provided at the roof. The roof trusses are spaced at 32 inches on center and are supported by glu-laminated girders that are supported by wood posts. Determine the following: The roof live load for the roof trusses in terms of pounds per foot along the length of the truss. Apply any applicable roof live load reductions. The roof live load for the interior glu-laminated girder in terms of pounds per foot along the length of the girder. Apply any applicable roof live load reductions. а. b. The roof live load for a perimeter column in terms of pounds. Apply any applicable roof live load reductions. 40'-0" Roof trusses Perimeter Column Interior glu laminated girder 30'-0" 30'-0"

Answer 1

Live Load Slope of roof 20 psf 0.5 inches of rise per foot CALCULATIONS Tributary area of structural member A = 2.67 30 x 80.1 ft? Reduction Factors R = As per ASCE7, R = 1 for A, <=200 ft 1.2-0.0014, for 200 ft'<At<600ft? 0.6 for A,>=600 ft R = As per ASCE7, 1 R2 = 1 1.2-0.05F 0.6 for F<=4 for 4<F<12 for F>=12 Reduced roof live load = LOR, R2 where 12 <=Lr<=20 20 psf Therefore, load on typical joist 2.67 20 psf x 53.4 plf

Le = Live Load Slope of roof 20 psf 0.5 inches of rise per foot CALCULATIONS Tributary area of structural member Aca 40 x 30 1200 ft Reduction Factors 0.6 R = As per ASCE7, R1 = 1 for A, <=200 ft? 1.2-0.001A, for 200 ft?<At<600ft? for A >=600 ft 0.6 R2 = As per ASCE7, 1 R2 = 1 1.2-0.05F 0.6 for F<=4 for 4<F<12 for > =12 Reduced roof live load L, = LORR2 where 12 <=Lr<=20 12 psf Therefore, load on typical joist 30 12 psf x 360 plf

Live Load Slope of roof 20 psf 0.5 inches of rise per foot CALCULATIONS Tributary area of structural member A = 15 20 X 300 ft? Reduction Factors R = As per ASCEZ, 0.9 R1 = 1 for A, <=200 ft 1.2-0.0014, for 200 ft'<At<600ft? 0.6 for A, >=600 ft R = As per ASCE7, 1 R2 = 1 1.2-0.05F 0.6 for F<=4 for 4<F<12 for F>=12 Reduced roof live load = LRR2 where 12 <=Lr<=20 18 psf Axial load on column 18 X 5400 lb A