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# lecture10 - Lecture 10 – Design Lecture 10 – Design...

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Unformatted text preview: Lecture 10 – Design Lecture 10 – Design Reinforced Beams Reinforced Beams June 23, 2003 CVEN 444 Lecture Goals Lecture Goals Examples of Singly Reinforced Rectangular Beam Known section dimensions Unknown section dimensions Design of Doubly Reinforced Beams Known section dimensions Unknown section dimensions Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Design a singly reinforced beam, which has a moment capacity, M u = 250 k-ft, f c = 4.5 ksi, and f y = 50 ksi. Use a b = 0.55d and determine whether or not it is sufficient space for the tension steel. Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Select a c/d ratio for the tension component to dominate. Chose c/d=0.25 c 1 4000 psi 0.85 0.05 1000 psi 4500 psi 4000 psi 0.85 0.05 1000 psi 0.825 f β - =- - =- = ( 29 1 0.825 0.25 0.20675 c k d β ′ = = = Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Calculate R u for the beam ( 29 ( 29 ( 29 u c 0.85 1 2 0.20675 0.85 4.5 ksi 0.20675 1 2 0.7076 ksi k R f k ′ ′ =- =- = Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Calculate the b d 2 U 2 N u u 3 12 in 250 k-ft ft 0.9 4711 in 0.7076 ksi M M bd R R φ = = = = Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Calculate d, if b = 0.55d 3 3 3 3 4711 in 0.55 4711 in 20.46 in. 0.55 d d = ⇒ = = If b = 0.55(20.46 in.) = 11.25 in., so use b = 12 in. and d = 20.5 in. and h = 23 in. ( 29 0.25 0.25 20.5 in 5.125 in. c d = = = Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Calculate A s for the beam ( 29 ( 29 ( 29 ( 29 c 1 s y 2 0.85 0.85 4.5 ksi 12 in. 0.825 5.125 in. 50 ksi 3.88 in f b c A f β = = = Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Look at a series of bars and calculate A s for the beam for a single layer. ( 29 b stirrup 2 1 2 cover b n d d =- + + The cover is 1.5 in. and use d = 3/8 in. stirrup. Example - Singly RC Beam Example - Singly RC Beam (Unknown Dimensions I) (Unknown Dimensions I) Look at a series of bars and calculate A s for the beam for a single layer....
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lecture10 - Lecture 10 – Design Lecture 10 – Design...

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