Determine the live load support reactions at the fixed post base

 Ignore the weight of bolt, caps, compartments, etc. and the voids in member – only consider the gross

self-weight of the main structural tubing (mast arm and post).

▪ Ignore the 12” portion of the post that extends above the mast arm connection

▪ The bottom of the post is a fixed connection to the foundation

EAS211 Homework 3 201804

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▪ Assume that the horizontal wind load only acts on the vertical post. Although the post is tapered, you

will treat the wind load as two uniformly distributed loads, as follows:

– Bottom of Post (0’-20’ height above base): 20 lbs/ft

– Top of Post (20’+ height above base): 30 lbs/ft

▪ Use the following geometry and loading parameters:

– Mast Arm Length: 30.0 ft (Horizontal Projection)

– Post Riser Height: 24.0 ft (Vertical)

– Attached Signs/Signals: The following sign/signals are supported by the mast arm

Type Horiz. Distance From Post Centerline (ft) Weight (lbs)

30”x36” Sign 29.5 100

5-Section Head 26.5 300

30”x36” Sign 21.5 100

3-Section Head 18.5 200

3-Section Head 10.5 200

Tasks to complete:

A) “Dead” Load: considering only the self-weight of the mast arm and the post

a. Provide a loading diagram showing the dead loading on the mast arm and post. Note that there

should be linearly varying loads for the weight of both members.

b. Determine the dead load support reactions at the fixed post base

B) “Live” Load: considering only the weight of the signs and signals (“heads”)

a. Provide a loading diagram showing the live loading on the mast arm and post.

b. Determine the live load support reactions at the fixed post base

C) “Wind” Load: considering only the wind load acting on the vertical post

a. Provide a loading diagram showing the wind loading on the post.

b. Determine the live load support reactions at the fixed post base

c. The assumed/prescribed wind loading for this 2d example is very simplified. Provide a 3d

sketch of the mast arm and post structure, then discuss/conclude which of the 6 possible

support reactions (3 forces, 3 moments) could be caused by wind loading. Use complete

sentences to explain your reasoning. Calculations are not required, but some basic equations in

conjunction with your diagram may be helpful to support your conclusion.

EAS211 Homework 3 201804

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