lecture25 - Lecture25DesignofTwo WayFloorSlabSystem...

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    Lecture 25 -  Design of Two- Lecture 25 -  Design of Two- Way Floor Slab System Way Floor Slab System August 6, 2003 CVEN 444
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    Lecture Goals Lecture Goals Example of DDM Panel Design
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    Example 1 Example 1   Design an interior panel of the two-way slab for the floor system.The floor consists of six panels at each direction, with a panel size 24 ft x 20 ft. All panels are supported by 20 in square columns. The slabs are supported by beams along the column line with cross sections. The service live load is to be taken as 80 psf and the service dead load consists of 24 psf of floor finishing in addition to the self-weight. Use f c = 4 ksi and f y = 60 ksi
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    Example 1 Example 1  – Previous Example Previous Example The cross-sections are: h = 7 in.
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    Example 1 Example 1  – Previous Example Previous Example The resulting cross section:
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    Example 1  Example 1  Previous Example Previous Example The thickness was calculated in an earlier example. Generally, thickness of the slab is calculated at the for the external corner slab. So use h = 7 in.
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    Example 1- Loading  Example 1- Loading  The weight of the slab is given as. 2 3 2 u 2 2 2 2 lb 1 ft lb lb 24 7.0 in. 150 111.5 ft 12 in. ft ft lb lb 1.2 1.6 1.2 111.5 1.6 80 ft ft lb kips 262 0.262 ft ft DL w DL LL  = + =   = + = + =
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    Example 1 – calculation d Example 1 – calculation d Compute the average depth, d for the slab. Use an average depth for the shear calculation with a #4 bar (d = 0.5 in) ( 29 b cover / 2 7.0 in. 0.75 in. 0.5 in./ 2 6.0 in. d h d d = - - = - - =
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    Example 1 – One-way shear Example 1 – One-way shear The shear stresses in the slab are not critical. The critical section is at a distance d from the face of the beam. Use 1 ft section. ( 29 ( 29 ( 29 u u 2 beam width 12 ft. 1 ft. 2 1 ft 16 in. 1 ft 12 in. 0.262 k/ft 12 ft. 6 in. 1 ft. 2 12 in. 2.84 k V w d = - - = - - =
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    Example 1 – One-way shear Example 1 – One-way shear The one way shear on the face of the beam. ( 29 ( 29 ( 29 ( 29 c c 2 1 kip 0.75 2 3000 12 in. 6 in. 1000 lb 5.92 k 2.84 k OK. V f bd φ = = =
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    Example 1 – Strip size Example 1 – Strip size Determine the strip sizes for the column and middle strip. Use the smaller of l 1 or l 2 so l 2 = 20 ft ( 29 ( 29 ( 29 ( 29 in 168 ft 14 ft 5 2 ft 24 in 120 ft 10 ft 5 2 ft 20 s l = - = = - = b b ft 5 4 ft 20 4 2 = = = l l Therefore the column strip b = 2( 5 ft) = 10 ft (120 in) The middle strips are
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    Example 1 – Strip Size Example 1 – Strip Size Calculate the strip sizes
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    Example 1 – Static Moment  Example 1 – Static Moment  Computation Computation Moment M o for the two directions.
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lecture25 - Lecture25DesignofTwo WayFloorSlabSystem...

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