Structural Analysis ( update )

Structural Analysis

Exam #2

Take-Home

Due in class Wednesday 9.25.2019 by 2: 40pm (BE ON TIME)

1. Your team is designing the lateral load-resisting system for a two-story office building. To do so,

you need to determine the wind loads on the lateral load-resisting elements. At this preliminary

stage, consider the floor and roof diaphragms to be flexible, and consider the wind pressure to

be uniform. Note that the south and east walls have been cut away so that we can see the

system supporting them.

I. When the wind blows from the south, it creates a uniform pressure of 30 psf on the

south elevation.

a. Convert the applied wind pressure into line loads that act at each diaphragm

level on the windward side.

b. Then convert the line loads into point loads that act at the locations where the

diaphragms meet the lateral load-resisting elements.

II. When the wind blows from the east, it creates a uniform pressure of 20 psf on the east

elevation.

a. Convert the applied wind pressure into line loads that act at each diaphragm

level on the windward side.

b. Then convert the line loads into point loads that act at the locations where the

diaphragms meet the lateral load-resisting elements.

2. The contractor for a new high-rise building must temporarily brace the large excavation for the

basement. Your firm has been selected to design the bracing. The geotechnical report

recommends that you design for an effective lateral soil pressure of 3.25 kN/m2 per meter of

depth. The senior engineer on your team recommends that you use braces spaced every 5 m

along the length of the excavation. Your job is to find the unfactored force generated on one

brace at each level.

3. Provide the following for the beam loaded as such below.

a. Derive the equations for the shear and moment for the beam. (Hint: should be 3/each)

b. Construct the shear and moment diagrams for the beam and label values and locations.

c. Identify at least three features of the shear diagram and three features of the moment

diagram that suggest you have a reasonable answer.

d. Determine the peak moment due to the live load and its location.

e. Make a comprehensive argument that the peak moment found in part (h) is reasonable.

4. In order to design the cross- member and the post for the traffic signal structure below, you will

need to know the internal forces due to the self-weight. Use the diagram below to answer the

following questions:

a. Construct the axial force, shear, and moment diagrams for the frame with full self-weight.

Label values and locations.

b. Identify at least two features of the axial force, shear force, and moment diagrams that

suggest you have a reasonable answer. (so 6 total)

c. Determine the peak moment due to the full self-weight and its location.

d. Make a comprehensive argument that the peak moment found is reasonable.

5. For the truss below a) identify all the zero-force members (if any) and b) Solve for all the

members in the truss below using method of joints.

6. For the truss below a) identify all the zero-force members (if any) and b) solve for members GI,

FG, CE, CF, EF and DF.