2.1

A 20-inch-diameter, spirally reinforced column with 1 -inch cover to the spiral is reinforced with 10 No. 9 bars. The concrete strength is 5000 pounds per square inch and the tensile strength of the reinforcement is 60,000 pounds per square inch. The unsupported length of the column is 9 feet and it is braced against side sway.

1. What is the effective length factor?

   1. 0.65

   2. 0.80

   3. 1.00

   4. 1.20

2. The column slenderness ratio is most nearly:

   1. 19.4

   2. 21.0

   3. 21.6

   4. 22.0

3. The column supports only axial load and the design axial load strength is given most nearly by:

   (Do not use tables or charts)

   1. 600 kips

   2. 800 kips

   3. 1000 kips

   4. 1200 kips

4. The minimum permitted diameter of the spiral reinforcement is:

   1. inch

   2. ? inch

   3. inch

   4. ? inch

5. The maximum allowable pitch of the spiral is most nearly:

   1. 1.25 inches

   2. 1.50 inches

   3. 1.75 inches

   4. 2.00 inches

   If factored moments of M _{1 b} = M _{2 b} = 250 kip-feet are applied at the ends of the column, which is bent in single curvature, then:

6. The design axial load strength is most nearly: (Tables or charts may be used)

   1. 785 kips

   2. 835 kips

   3. 885 kips

   4. 935 kips

   Assuming factored moments from gravity loads of M _{1 b} = M _{2 b} = 250 kip-feet are applied at the ends of the column, which is 12 feet long and is bent in single curvature and has a factored axial load of 700 kips...