lecture23 - andTwowaySlabs August1,2003 CVEN444...

Info icon This preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
    Lecture 23 -  Slender Columns  Lecture 23 -  Slender Columns  and Two-way Slabs and Two-way Slabs August 1, 2003 CVEN 444
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
    Lecture Goals Lecture Goals Slender Column Design One-way and two-way slab Slab thickness, h 
Image of page 2
    Design of Long Columns- Example Design of Long Columns- Example A rectangular braced column of a multistory frame building has floor height l u =25 ft. It is subjected to service dead-load moments M 2 = 3500 k-in. on top and M 1 =2500 k-in. at the bottom. The service live load moments are 80% of the dead-load moments. The column carries a service axial dead-load P D = 200 k and a service axial live-load P L = 350 k. Design the cross section size and reinforcement for this column. Given Ψ A = 1.3 and Ψ B = 0.9. Use a d’=2.5 in. cover with an sustain load = 50 % and f c = 7 ksi and f y = 60 ksi.
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
    Design of Long Columns- Example Design of Long Columns- Example Compute the factored loads and moments are 80% of the dead loads ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 u D L 1u D L 2u D L 1.2 1.6 1.2 200 k 1.6 350 k 800 k 1.2 1.6 1.2 2500 k-in 1.6 0.8 2500 k-in 6200 k-in. 1.2 1.6 1.2 3500 k-in 1.6 0.8 3500 k-in 8680 k-in. P P P M M M M M M = + = + = = + = + = = + = + =
Image of page 4
    Design of Long Columns- Example Design of Long Columns- Example Compute the k value for the braced compression members Therefore, use k = 0.81 ( 29 ( 29 ( 29 A B min 0.7 0.05 0.7 0.05 1.3 0.9 0.81 1.0 0.85 0.05 0.85 0.05 0.9 0.895 1.0 k k = + Ψ + Ψ = + + = = + Ψ = + =
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
    Design of Long Columns- Example  Design of Long Columns- Example  Check to see if slenderness is going to matter. An initial estimate of the size of the column will be an inch for every foot of height. So h = 25 in. ( 29 ( 29 ( 29 n 0.81 25 ft 12 in./ft 32.4 r 0.3 25 in. 6200 k-in. 32.4 34 12 25.43 8680 k-in. kl = = - = We need to be concerned with slender columns
Image of page 6
    Design of Long Columns- Example  Design of Long Columns- Example  So slenderness must be considered. Since frame has no side sway, M 2 = M 2ns , δ s = 0 Calculate the minimum M 2 for the ratio computations. ( 29 ( 29 ( 29 2,min u 2 0.6 0.03 800 k 0.6 0.03 25 in. 1080 k-in. 8680 k-in. M P h M = + = + = =
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
    Design of Long Columns- Example  Design of Long Columns- Example  Compute components of concrete The moment of inertia of the column is ( 29 1.5 1.5 c c 6 3 33 33 150 7000 5.07x10 psi 5.07x10 ksi E w f = = = ( 29 ( 29 3 3 g 4 25 in. 25 in. 12 12 32552 in bh I = = =
Image of page 8
    Design of Long Columns- Example Design of Long Columns- Example Compute the stiffness, EI ( 29 ( 29 3 4 c g d 7 2 0.4 5.07x10 ksi 32552 in 0.4 1 1 0.5 4.4x10 k-in E I EI β = = + + =
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
    Design of Long Columns- Example Design of Long Columns- Example The critical load (buckling), P cr , is ( 29 ( 29 ( 29 2 7 2 2 cr 2 2 u 4.4x10 k-in 12 in. 0.81 25 ft ft 7354.3 k EI P kl π π = = =
Image of page 10
    Design of Long Columns- Example Design of Long Columns- Example Compute the coefficient, C m , for the magnification δ coefficient 1 m 2 0.6 0.4 6200 k-in.
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern