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Concrete Beams Design Problem 2 - Determine the stirrup steel area for a concrete beam:
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Size the vertical stirrup size of a rectangular beam with dimensions b = 9 in, d = 16.5 in and h = 19in if it must carry a maximum shear load of Vu = 25000 lb. Use 3500 psi concrete and 40,000 psi steel.
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1. From the concrete beams submenu open the concrete shear strength calculation, ConcShearStrength.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The concrete shear strength of the beam, Vc = 17,570.757 lb.
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2. Next from the concrete beams submenu open the required steel shear strength calculation, ReqSteelShear.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The required steel shear strength of the shear reinforcement, (stirrups), Vs = 11,841.765 lb.
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3. Next determine the stirrup spacing of the proposed stirrups. From the concrete beams submenu open the maximum stirrup spacing calculation, MaxStirrupSpacing.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The maximum stirrup spacing, s = 8.25 in. Use 8 in.
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4. Next determine the required area of steel for vertical stirrups spaced at 8 in. From the concrete beams submenu open the required vertical shear reinforcement calculation, AreaShearReinf.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The required steel area, Av = 0.144 in^2. #3 stirrups have an area of 0.110 in^2 per leg for a total area of 2 X 0.110 in^2 = 0.220 in^2. Use #3 stirrups.
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5. Finally, check the minimum required area of steel shear reinforcement. From the concrete beams submenu open the required minimum area of shear reinforcement calculation, MinAreaShearReinf.aspx. Input the "Title" of the calculation, the "Designer/Checker" information and the variables.
Click on the "Calculate" button and read the results. The minimum required shear steel area, Av = 0.090 in^2. The required shear steel Av = 0.144 in^2 is greater than the minimum shear steel required so the design is Ok.
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6. Summary
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To meet the shear reinforcement area requirement of Av = 0.144 in^2, use #3 vertical stirrups with an area of 0.220 in^2, spaced at s = 8 in.
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