AECT480-Lecture%203 - Lecture 3 Flexural Members Flexural...

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Lecture 3 - Page 1 of 9 Lecture 3 – Flexural Members Flexural members are those that experience primarily bending stresses, such as beams. A typical rectangular reinforced concrete beam is shown below: Concrete cover = ¾” 2” as per ACI reqmts. Depth to steel “d” Height “h” Width “b” Section A-A Hanger bars (#4 or #5 bars) Stirrup bars (used to prevent diag. tension cracks) spaced at d/2 apart Tension bars “A s
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Lecture 3 - Page 2 of 9 Sometimes, 2 (or more) rows of main tension bars are necessary. It is important to provide minimum adequate cover around all reinforcing bars so that these bars can properly bond with the concrete. ACI 318 dictates that the minimum spacing between bars is 1.5 times the maximum concrete aggregate size . Typical concrete batches use a maximum aggregate size of ¾” diameter, so then the minimum bar spacing = 1.5(¾”) = 1 ”. Below is a sketch of a typical concrete beam with 2 rows of tension bars: Min. bar spacing Min. bar spacing Depth to centroid of steel “d” Height “h” Tension bars “A s
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Lecture 3 - Page 3 of 9 A s = Total cross-sectional area of all tension bars, in 2 d = depth to center of tension bars, inches = h – (concrete cover) – (stirrup bar dia.) – ½(tension bar dia.) f y = yield stress of reinforcing bars = 60 KSI for ASTM A615 Grade 60 bars = 40 KSI for ASTM A615 Grade 40 bars ρ actual = Rho actual = actual ratio of tension steel to effective concrete area = bd A s ρ min = Rho minimum = minimum allowable ratio of tension steel per ACI 318 = y f 200 where f y = PSI
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Lecture 3 - Page 4 of 9 Example 1 GIVEN : A rectangular concrete beam is similar to the one shown above.
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This note was uploaded on 05/01/2010 for the course CEE 615 taught by Professor Parra during the Winter '09 term at University of Michigan-Dearborn.

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AECT480-Lecture%203 - Lecture 3 Flexural Members Flexural...

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