Mathcad - Homework #4 Part 1 Solution 2010

# Mathcad - Homework #4 Part 1 Solution 2010 - PRESTRESSED...

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PRESTRESSED CONCRETE DESIGN CE486/586 - Homework #4 Solution 1.) 10DT32 Concrete Strength at Transfer of Prestress 188-D1 Strand Pattern A ps 18 0.153 in 2 := A ps 2.754 in 2 = f pu 270ksi := f pj 75% f pu := f pj 202.50 ksi = ES 15ksi := f pi f pj ES := f pi 187.50 ksi = P i f pi A ps := P i 516.38 kip = L DT 74ft := L transfer 2ft := Transfer Length P i x () P i x L transfer xL transfer if P i otherwise := Valid for half the span. Prestressing Strand Pattern, Single Harp Pattern y e 14.39in := y c 4.00in := y s x y e y e y c L DT 2 x := y s L DT 2 4.00 in = Valid for half the span. 10DT32 Section Properties - PCI Design Handbook Page 2-18 A DT 615in 2 := I DT 59720 in 4 := y t 10.02in := y b 21.98in := w DT 641plf := S t 5960in 3 := S b 2717in 3 := M DT x w DT x 2 L DT x := Homework #4 Part 1 Solution 2010.xmcd Page 1

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Stresses at Transfer of Prestress ex () y b y s x := e 0.4 L DT 15.90 in = e 0.5 L DT 17.98 in = f t x P i x 1 A DT S t M DT x S t + := f b x P i x 1 A DT S b + M DT x S b := 0 10 20 30 0 11 0 3 × 21 0 3 × 31 0 3 × f t x psi f b x psi x f b L transfer 2185 psi = f b 0.5L DT 2319 psi = Plot shows no tension at transfer of prestress. Compressive stresses are controlled at midspan. Determine concrete strength required at transfer of prestress. Specify 3900 or 4000 psi at transfer of prestress. Typcially, 4000 psi is minimum at transfer for a precast prestressed member. f' ci_reqd f b 0.5L DT 0.6 := f' ci_reqd 3865 psi = f' ci_reqd f b L transfer 0.7 := f' ci_reqd 3121 psi = Homework #4 Part 1 Solution 2010.xmcd Page 2

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Mathcad - Homework #4 Part 1 Solution 2010 - PRESTRESSED...

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