concrete design

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CE 334 – Week 14 Columns Homework Quiz Name:________________ 1. True or false: ACI only permits tension-controlled failure modes in columns. 2. What is the φ factor for a spiral column? 3. Name the 4 principles used to calculate the strength of a column. 4. How do the equilibrium equations for a column have to be adjusted compared to the equilibrium equations for a beam? 5. In addition to axial load and the primary bending moments from the applied loads, what other effect must long (slender) columns be designed for? 6. How does ACI classify a column as long or short? 7. In a short column, what factors control the maximum load supported? 8. Describe what causes the secondary P-Δ moment in a long column. CE 334 – Week 14 Columns Homework Quiz Name:________________ 9. Name three types of columns. 10. Describe a composite column. 11. True or false: ties increase the strength of a column. 12. Are tied or spiral columns better for earthquake-prone areas? 13. Why is the failure mode of a spiral column more ductile than the failure mode of a tied column? 14. What is the equation for axial load capacity of a reinforced column? 15. Why is the capacity reduction factor φ smaller for a column than for a beam? 16. Why does the ACI Code limit the design capacity of an axially loaded column to 80 or 85 percent of its actual strength? 17. What are the maximum and minimum percentages of steel that ACI permits a column to be reinforced with? CE 334 – Week 14 Columns Homework Quiz Name:________________ 18. From a practical standpoint, what is the minimum possible column dimension? 19. What is the smallest size tie permitted by the ACI Code for the column shown? What would be the required spacing of those ties? 20. True or false: the confining effect of spiral reinforcement causes the concrete compressive strength to increase. 21. Define plastic centroid. 22. When is the column capacity reached (i.e. when does failure occur)? 23. 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. CE 334 – Week 14 Columns Homework Quiz Name:________________ 24. True or false: Columns with axial load plus bending moment can have all of the column cross section in compression. 25. What is an interaction diagram?
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CE 334 –
Week 14 Columns Homework Quiz

Name:________________

1. True or false: ACI only permits tension-controlled failure modes in columns.
False
2. What is the φ factor for a spiral column?
The strength of short columns is controlled by the strength of the material and the
geometry of the cross section. Reinforcing rebar is placed axially in the column to
provide additional axial stiffness. Accounting for the additional stiffness of the steel, the
nominal loading capacity Pn for the column in terms of the maximum compressive stress
of the concrete fc', the yield stress of the steel fy, the gross cross section area of the
column Ag, and the total cross section area of the steel rebar Ast
3. Name the 4 principles used to calculate the strength of a column.
Strut with pinned ends
One end fixed and the other free
Strut with fixed ends
One end fixed, the other pinned
4. How do the equilibrium equations for a column have to be adjusted compared to the
equilibrium equations for a beam?
In the equilibrium equations for a column, N is the axial force resulting acting in a tensile
manner (opposite in direction to the compressive resultant f). While equilibrium
equations for a beam, In order to maintain a segment of a beam in equilibrium, there
exists an internal vertical force V at the cut to satisfy the equation in the y-direction. This
internal force, which is vertical to the axis of the beam, is called the shearing force.

CE 334 –
Week 14 Columns Homework Quiz

Name:________________

5. In addition to axial load and the primary bending moments from the applied loads,
what other effect must long (slender) columns be designed for?
Slender and short are the two types of columns classified on the basis of slenderness
ratios as mentioned in sec.10.21.5 of Lesson 21. Columns having both lex/D and ley/b
less than twelve are designated as short and otherwise, they are sle...


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