A posttensioned concrete beam with section shown contains prestressing cables 800 mm² with initial prestress of 100 MPa. The beam is supported over a span of 16 m. The centroid of the section is located 240 mm from the extreme compression fiber and the cables are located 110 mm from the bottom of the beam. It is to carry a dead load of 3.5 kN/m and a live load of 4.75 kN/m. The losses of prestress is about 15%. Calculate the stress at service loads of prestress for the bottom fiber. 500 mm 600 mm A = 100,000 mm2 I = 3600 x 106 mm4

Structural Analysis
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Chapter2: Loads On Structures
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Hello is my answer key correct on the stress at  service load on bottom and  top fiber

Can you indicate which one is the service load and  transfer of pre stress

P Рес
68,000(250)(240)
3600,000,000
68,000 68,000(250)(360)
3600,000,000
68,000
ft
100,000
= 0.45 MPa
Рес
fo = --+
-2.38 MPa
A' I
100,000
1m
weight of beam = 24 (100,000 mm²)
(1000mm)
= 2.4 kN/m³
w = 3.5 + 4.75 + 2.4 = 10.65 kN/m
10.65(16)?
M =
= 340.80 kN – m
8
Mc
340.8x10 (240)
ft =
3600,000,000
= -22.72 MPa
Mc
340.8x10°(360)
fo =T
= 34.08 MPa
3600,000,000
P = 160,000(0.90)(0.9) = 129,600 lbs
bh 14(24)3
= 16,128
12
12
Transcribed Image Text:P Рес 68,000(250)(240) 3600,000,000 68,000 68,000(250)(360) 3600,000,000 68,000 ft 100,000 = 0.45 MPa Рес fo = --+ -2.38 MPa A' I 100,000 1m weight of beam = 24 (100,000 mm²) (1000mm) = 2.4 kN/m³ w = 3.5 + 4.75 + 2.4 = 10.65 kN/m 10.65(16)? M = = 340.80 kN – m 8 Mc 340.8x10 (240) ft = 3600,000,000 = -22.72 MPa Mc 340.8x10°(360) fo =T = 34.08 MPa 3600,000,000 P = 160,000(0.90)(0.9) = 129,600 lbs bh 14(24)3 = 16,128 12 12
A posttensioned concrete beam with section shown contains prestressing cables 800 mm? with initial prestress of 100 MPa. The
beam is supported over a span of 16 m. The centroid of the section is located 240 mm from the extreme compression fiber and the
cables are located 110 mm from the bottom of the beam. It is to carry a dead load of 3.5 kN/m and a live load of 4.75 kN/m. The
losses of prestress is about 15%. Calculate the stress at service loads of prestress for the bottom fiber.
500 mm
600 mm
100,000 mm2
I = 3600 x 106 mm4
A =
Transcribed Image Text:A posttensioned concrete beam with section shown contains prestressing cables 800 mm? with initial prestress of 100 MPa. The beam is supported over a span of 16 m. The centroid of the section is located 240 mm from the extreme compression fiber and the cables are located 110 mm from the bottom of the beam. It is to carry a dead load of 3.5 kN/m and a live load of 4.75 kN/m. The losses of prestress is about 15%. Calculate the stress at service loads of prestress for the bottom fiber. 500 mm 600 mm 100,000 mm2 I = 3600 x 106 mm4 A =
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