Problem 3.  A composite bridge is constructed out of simply supported precast, pretensioned ASSHTO Type II (see the pdf file containing section properties data) beams and a cast-in-place reinforced concrete slab, as shown below.   The tendons are harped at 0.4L.  Check stresses at transfer at critical sections and at slab placement.  Later we will come back to this problem and determine critical stresses at full service load and nominal moment capacity and the cracking moment for the composite section.

Given:  f’ci = 4 ksi  f’c = 5 ksi (beam)

f’c = 3 ksi (slab)

 beam = 150 pcf

 slab = 150 pcf

fti = 0.190 ksi

fci = -2.4 ksi

fts = 0.530 ksi

fcs = -2.25 ksi

Pi = 551 kips

R = 0.85

Eccentricity at harping points and midspan = 8.89 in

Eccentricity = 0 at supports

18 ½ in diameter  stress relieved strands, fpu = 270 ksi  fpy = 230 ksi

Span length = 60 ft.

wL = 1.125 k/ft