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Concrete Columns Design Problem 1 - Design a short concrete column:
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Design a short spiral column to carry a factored load of 375 kips. Use 3000 psi concrete and 40,000 psi steel.
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1. From the concrete columns submenu open the column area calculation, ColumnArea.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The gross area, Ag = 178.307. The outside column diameter, Dg = 15.067 in. The column core diameter, Dc = 12.067 in. The steel reinforcement area, Ast = 3.566 sq in. Use Dg = 15.25 in and Dc = 12.25 in.
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2. Next, from the concrete columns submenu open the column spiral reinforcement ratio calculation, SpiralReinfRatio.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Use Ag = 3.14159((15.25)^2)/4 = 182.654 sq in and Ac = 3.14159((12.25)^2)/4 = 117.859 sq in. Click on the "Calculate" button and read the results. The reinforcement ratio, ps = 0.0186.
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3. Next determine the spiral pitch. From the concrete columns submenu open the concrete columns spiral pitch calculation, Spiralpitch.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Use 3/8 in rebar with an area of 0.11 sq in. Click on the "Calculate" button and read the results. The spiral pitch, s = 1.931 in. Use s = 1.75 in.
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4. Finally determine the clear space between spirals. From the concrete columns submenu open the concrete columns spiral clear distance calculation, SpiralClearDist.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The spiral clear distance = 1.375 in.
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5. Summary
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The outside column diameter is 15.25 in. The column core diameter is 12.25 in. The area of steel reinforcement, Ast = 3.57 sq in. ACI 318 requires at least six bars
to be used. Use six no. 7 bars with an area of 3.607 sq in. Use 3/8 inch spiral reinforcement with a spiral pitch equal to 1.75 inches and a clear space between spirals of 1.375 inches.
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