Mechanics Homework Engineering Department

ENES220 In-Class Exercise #6

November 2, 2016

Due on November 30, 2016

A 6 ft by 3 ft sign weighs

500 lb and is supported by

a 40-ft high pole. The

maximum wind pressure

against the sign is

calculated as 50 lb/ft2

when a storm hits. Your

task is to design the pole.

Be creative, but try to use

all the knowledge and

computer tools you have

learned in this and other

classes to do this project.

Design the pole by completing the following tasks:

1. Choose an appropriate material for the pole. [1.5] 2. Find typical values of the following mechanical properties for the pole and list your

references (books, web sites, apps, etc.): density, modulus of elasticity, Poisson’s ratio,

yield strength, ultimate strength. [1.5]

3. Select a pole cross section shape that will fit within a square area of 10 in by 10 in. For this cross section, calculate the area, moment of inertia, polar moment of inertia, and first

moment of the area. [3]

4. Determine the following mechanical parameters: a. Axial force (due to weight) [1.5] b. Torque (due to maximum wind pressure) acting on the pole [1.5] c. Contraction in the pole [1.5] d. Angle of twist in the pole [1.5] e. Maximum shear force and its location on the pole [1.5] f. Maximum bending moment and its location on the pole [1.5] g. Principal stresses at point A [3] h. Safety factor to design against yielding failure [3] i. Maximum deflection at top of pole [1.5] j. Maximum slope at top of pole [1.5]

5. After turning the pole 90°, draw the following graphs for the pole: [3] a. Shear force b. Bending moment

6. Check for buckling. Is there a possibility of buckling? [1.5] 7. Comment on overall design you chose in #2 and #3 above. List assumptions and

comment on them. [1.5]

Julie’s Office 8 in

10 in

40 ft

6 ft

3 ft

A

Section X-X

A

X X