Post-tensioned AASHTO Type II girders are to be used to support a deck with unsupported span equal to 10 meters. Two levels of Grade 250, 10 x 15.2 mm Ø 7-wire strand are used to tension the girders with 5 tendons per level, where the tendons on top stressed before the ones on the bottom. The girder is simply supported at both ends. The anchors are located 100 mm above the neutral axis at the supports while the eccentricity is measured at 400 mm at the midspan. The tendon profile follows a parabolic shape using a rigid metal sheathing. A concrete topping (slab) 130 mm thick is placed above the beam with a total tributary width of 4 meters. Use maximum values for ranges (table values). Assume that the critical section of the beam is at 0.45LDetermine the losses (friction loss, anchorage, elastic shortening, creep, shrinkage, relaxation). Determine the stresses at the top fibers @ critical section before placing a concrete topping, right after stress transfer. Determine the stress at the bottom fiber @ critical section of the beam, 2 months after stress transfer, before concrete topping.Determine the maximum tensile and compressive stress at the beam @ critical section after concrete topping. Given the following parameters:F’c = 5000 psiFu = 270 ksi ((Bonded, low-relaxation)Es = 29,000 ksiEc = 4,030 psiFj = 235 ksiA = 1x0.6” Ø 7-W.S. = 0.217 in2γc = 140 lbs/ft3ΔA = 3/8”RH = 33%
Post-tensioned AASHTO Type II girders are to be used to support a deck with unsupported span equal to 10 meters. Two levels of Grade 250, 10 x 15.2 mm Ø 7-wire strand are used to tension the girders with 5 tendons per level, where the tendons on top stressed before the ones on the bottom. The girder is simply supported at both ends. The anchors are located 100 mm above the neutral axis at the supports while the eccentricity is measured at 400 mm at the midspan. The tendon profile follows a parabolic shape using a rigid metal sheathing. A concrete topping (slab) 130 mm thick is placed above the beam with a total tributary width of 4 meters.
Use maximum values for ranges (table values). Assume that the critical section of the beam is at 0.45L
Determine the losses (friction loss, anchorage, elastic shortening, creep, shrinkage, relaxation).
Determine the stresses at the top fibers @ critical section before placing a concrete topping, right after stress transfer.
Determine the stress at the bottom fiber @ critical section of the beam, 2 months after stress transfer, before concrete topping.
Determine the maximum tensile and compressive stress at the beam @ critical section after concrete topping.
Given the following parameters:
F’c = 5000 psi
Fu = 270 ksi ((Bonded, low-relaxation)
Es = 29,000 ksi
Ec = 4,030 psi
Fj = 235 ksi
A = 1x0.6” Ø 7-W.S. = 0.217 in2
γc = 140 lbs/ft3
ΔA = 3/8”
RH = 33%
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