Romans 3:24
“But by the free gift of God’s grace all are put right with him through Christ Jesus, who sets them free.”
Prestressed Concrete Design
Final Exam
Name: _________________________________________________________ Instructor: Engr. Gamana
Section: Date:
Academic Integrity: Students who violate University rules on scholastic dishonesty are subject to disciplinary penalties,
including the possibility of failure in the course and/or dismissal from the University. Since such dishonesty harms the
individual, all students, and the integrity of the University, policies on scholastic dishonesty will be strictly enforced.
Solutions: Use 3 decimal places in your calculations, place your final answer with proper units on the first sheet of your
scratch paper, and credits will only be given for correct answers with correct solutions.
1. Member AB has a rectangular cross-section of 16 X 24 mm. For the loading shown with d = 55 mm and P = 30 kN.
a. Determine the normal stress at the midpoint of points H and K (a point 6 mm below K or 6 mm above H, not the
average of H and K).
b. Determine the major principal stress at the midpoint of points H and K (a point 6 mm below K or 6 mm above H,
not the average of H and K).
2. The section of a prestressed double-tee concrete floor joist is shown in the figure. Assume that there is a prestress loss
of 15% at service loads. Unit weight of concrete is 24.50 kN/m3 and f'c = 42 MPa
The properties of the double-tee sections are
A = 220,000 mm2 L = 11.5 m
I = 1890(106) mm4
Service loads on floor;
Dead load = 3.5 kPa
Live load = 7.5 kPa
Determine the prestressing force at the final stage, considering the bottom fiber of the midspan not to exceed
the modulus of rupture.
P
