Total Effective Prestress Force
Easyprestresseffective force
A prestressed member has 20 identical strands. Each strand has steel area 140 mm² and effective stress fpe = 1,100 MPa after all losses. Assume every strand is fully developed. What is the total effective prestress force Pe?
- A154 kN
- B5,208 kN
- C3,080 kN
- D3,920 kN
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Answer: C. 3,080 kN
Pe = n·Aps·fpe. Inputs: n = 20, Aps = 140 mm², fpe = 1,100 MPa (already after losses). Total area = 20(140) = 2,800 mm²; Pe = 2,800(1,100) = 3,080,000 N = 3,080 kN. Check: one strand carries 154 kN, and 20(154) = 3,080 kN. 154 kN is one strand only (strand count forgotten). 5,208 kN uses an ultimate strength of 1,860 MPa instead of the given effective stress. 3,920 kN uses a pre-loss jacking-type stress of 1,400 MPa instead of the stress after losses.
N kN
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