AECT250-Lecture 26

# AECT250-Lecture 26 - Lecture 26 One-Way Slabs A one-way...

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Lecture 26 - Page 1 of 13 Lecture 26 – One-Way Slabs A one-way slab is supported by parallel walls or beams, and the main tension reinforcing bars run parallel to the span. It looks like the following: The slab is designed as a series of 1’-0” wide beam “strips”. The analysis is similar to rectangular beams, except the width b = 12” and the height is usually on the order of 4” 10”. The main tension bars are usually #4, #5 or #6 bars. There are no stirrups in slabs, however, additional bars are placed perpendicular to the main tension bars to prevent cracking during the curing process. These bars are referred to as “shrinkage” or “temperature” bars and are also usually #4 or #5 bars. Tension rebar (parallel to span) Slab span Wall (or beam) Maximum spacing between main tension bars = smaller of Spacing reqd. for moment or 3 x slab thickness or 12” Maximum spacing between shrinkage bars = smaller of Spacing reqd. by analysis or 5 x slab thickness or 18” Slab thickness Shrinkage rebar (perpendicular to span) Shrinkage bar spacing Tension bar spacing

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Lecture 26 - Page 2 of 13 Design of Main Tension Bars : As previously mentioned, slabs are designed as a series of 1’-0” wide rectangular beam “strips” as shown below: Assuming the slab strip is a rectangular beam, then: M u = 0.9A s f y d(1 - c y act f f ' 59 . 0 ρ ) where: M u = Usable moment capacity of slab strip A s = Area of tension bars per 1’-0” width of slab f y = yield stress of rebar f’ c = specified compressive strength of concrete ρ act = bd A s Alternatively, the “Design Aid” Tables 1 and 2 from Lecture 24 may be used for analysis OR design. Span Tension bars d h b = 12” Slab strip Support beam
Lecture 26 - Page 3 of 13 Example 1 GIVEN : A one-way slab has a simple span = 8’-0” and the following materials and loads: Concrete f’ c = 4000 PSI #4 Grade 60 main tension bars and shrinkage bars Concrete cover = ¾” Superimposed floor SERVICE dead load = 38 PSF (not incl. slab wt.) Superimposed floor SERVIVE live load = 125 PSF REQUIRED : Design the slab, including thickness, main tension bars & shrinkage bars. Step 1 – Determine slab thickness “h” based on Table below

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## This note was uploaded on 05/05/2009 for the course AE AE250 taught by Professor Hultenius during the Fall '08 term at SUNY Delhi.

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AECT250-Lecture 26 - Lecture 26 One-Way Slabs A one-way...

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