A section of an OH line needs to be built on 46 ft. wood poles set 6 ft. deep in the ground. Each pole will carry two cross-arms. The upper cross-arm carries 4 conductors and the lower cross-arm carries 4 conductors. The top cross-arm will be 1 ft. below the pole top, and the lower cross-arm will be 3 ft. below the top cross-arm. The pole has a 24 in. circumference at the pole top and a 36 in. circumference at ground level. Also assume a wind velocity of 45 mi/h that exerts a transverse wind load of 0.72lb/ft on the top cross-arm and 0.51lb/ft on the lower cross-arm. The average span is 200 ft. The conductor used is of 0.81 in. diameter. The rated ultimate strength of the wood pole is 9000 lb/in2 and a safety factor of 2. Assume that the transverse wind load on the wood poles is 11 lb/ft². 1. Find the maximum allowable fiber stress in lb/in². 2. Find the height of the top cross-arm in feet. 3. Find the height of the lower cross-arm in feet. 4. Find the bending moment due to wind on the conductors in (lb.ft). 5. Find the bending moment due to wind on the pole in (lb.ft). 6. Find the internal resistant moment of the wood pole in (lb.ft). Drag and drop the true answer from row 1. Drag and drop the true answer from row 2. Drag and drop the true answer from row 3. Drag and drop the true answer from row 4. Drag and drop the true answer from row 5. Drag and drop the true answer from row 6.
A section of an OH line needs to be built on 46 ft. wood poles set 6 ft. deep in the ground. Each pole will carry two cross-arms. The upper cross-arm carries 4 conductors and the lower cross-arm carries 4 conductors. The top cross-arm will be 1 ft. below the pole top, and the lower cross-arm will be 3 ft. below the top cross-arm. The pole has a 24 in. circumference at the pole top and a 36 in. circumference at ground level. Also assume a wind velocity of 45 mi/h that exerts a transverse wind load of 0.72lb/ft on the top cross-arm and 0.51lb/ft on the lower cross-arm. The average span is 200 ft. The conductor used is of 0.81 in. diameter. The rated ultimate strength of the wood pole is 9000 lb/in2 and a safety factor of 2. Assume that the transverse wind load on the wood poles is 11 lb/ft². 1. Find the maximum allowable fiber stress in lb/in². 2. Find the height of the top cross-arm in feet. 3. Find the height of the lower cross-arm in feet. 4. Find the bending moment due to wind on the conductors in (lb.ft). 5. Find the bending moment due to wind on the pole in (lb.ft). 6. Find the internal resistant moment of the wood pole in (lb.ft). Drag and drop the true answer from row 1. Drag and drop the true answer from row 2. Drag and drop the true answer from row 3. Drag and drop the true answer from row 4. Drag and drop the true answer from row 5. Drag and drop the true answer from row 6.
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:A section of an OH line needs to be built on 46 ft. wood poles set 6 ft. deep in the ground. Each pole will carry two cross-arms. The upper cross-arm carries 4 conductors and the lower cross-arm
carries 4 conductors. The top cross-arm will be 1 ft. below the pole top, and the lower cross-arm will be 3 ft. below the top cross-arm. The pole has a 24 in. circumference at the pole top and a 36
in. circumference at ground level. Also assume a wind velocity of 45 mi/h that exerts a transverse wind load of 0.72lb/ft on the top cross-arm and 0.511b/ft on the lower cross-arm. The average
span is 200 ft. The conductor used is of 0.81 in. diameter. The rated ultimate strength of the wood pole is 9000 lb/in2 and a safety factor of 2. Assume that the transverse wind load on the wood
poles is 11 lb/ft².
1. Find the maximum allowable fiber stress in lb/in².
2. Find the height of the top cross-arm in feet.
3. Find the height of the lower cross-arm in feet.
4. Find the bending moment due to wind on the conductors in (lb.ft).
5. Find the bending moment due to wind on the pole in (lb.ft).
6. Find the internal resistant moment of the wood pole in (lb.ft).
3750 4000 3800 4500
39 37 38 41
35 38 36 34
37530 32912 43750 37152
5247 6111 4720 6317
55016 38888 67546 55395
Drag and drop the true answer from row 1.
Drag and drop the true answer from row 2.
Drag and drop the true answer from row 3.
Drag and drop the true answer from row 4.
Drag and drop the true answer from row 5.
Drag and drop the true answer from row 6.
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VIEWStep 3: Calculate bending moment due to wind on the conductors
VIEWStep 4: Calculate bending moment due to wind on the pole
VIEWStep 5: Calculate internal resistant moment of the wood pole
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