# concrete design

- True or false: ACI only permits tension-controlled failure modes in columns.

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- What is the φ factor for a spiral column?

- Name the 4 principles used to calculate the strength of a column.

- How do the equilibrium equations for a column have to be adjusted compared to the equilibrium equations for a beam?

- In addition to axial load and the primary bending moments from the applied loads, what other effect must long (slender) columns be designed for?

- How does ACI classify a column as long or short?

- In a short column, what factors control the maximum load supported?

- Describe what causes the secondary P-Δ moment in a long column.

- Name three types of columns.

- Describe a composite column.

- True or false: ties increase the strength of a column.

- Are tied or spiral columns better for earthquake-prone areas?

- Why is the failure mode of a spiral column more ductile than the failure mode of a tied column?

- What is the equation for axial load capacity of a reinforced column?

- Why is the capacity reduction factor φ smaller for a column than for a beam?

- Why does the ACI Code limit the design capacity of an axially loaded column to 80 or 85 percent of its actual strength?

- What are the maximum and minimum percentages of steel that ACI permits a column to be reinforced with?

- From a practical standpoint, what is the minimum possible column dimension?

- What is the smallest size tie permitted by the ACI Code for the column shown? What would be the required spacing of those ties?

- True or false: the confining effect of spiral reinforcement causes the concrete compressive strength to increase.

- Define plastic centroid.

- When is the column capacity reached (i.e. when does failure occur)?

- True or false: Columns with axial load plus bending moment can have one side of the column cross section in tension and one side in compression.

- True or false: Columns with axial load plus bending moment can have all of the column cross section in compression.

- What is an interaction diagram?