8

ft = _ P (i £c£^ _ MD + MSD MCSD + Ml f — Ac V r2 ) St Sc

Mcsd — superimposed dead load — 0 in this case

10,337

2,177,288

— +816 . 7, say 817 psi (T) (5 .4 MPa) < ft — 849 psi, OK

D. Composite slab stresses. Precast double-T concrete modulus is

Ec — 57,000yf — 57,000p5,000 — 4.03 x 106 psi (3 . 8 x 104 MPa) Situ-cast slab concrete modulus is

Ec — 57,000p3ffiXX) — 3 .12 x 106 psi (2 . 2 x 104 MPa)

Modular ratio

Sc for 2-in. slab top fibers — 8,152 in.3 from data . Scb for 2-in. slab bottom fibers — 10,337 in .3 from before for top of precast section.

Stress fl at top slab fibers = nML

cs Sct

8,152

Stress fCsb at bottom slab fibers

2,177,288 10,377

0 0

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