simply supported on a span of 7.5 m. and pre tensioned with one tendon in each stem with an initial force of 745 kN each, located at 75 mm above the bottom fiber, loss of stress at service load is 18%. Load imposed on the joists are: Dead load = 2.3 kPa Live load = 6 kPa Properties of DT: A = 200,000 mm² yt = 88 mm a = 2.4 m I= 1880 x 106 mm4 yb = 267 mm a=2.4 m N.A. 75 mm 192 mm 88 mm 267 mm a. Compute the stress at the bottom fibers of the DT at mid-span due to the initial pre stressing force alone. b. Compute the stress at the bottom fibers of the DT at mid-span due to the service loads and pre stress force. c. What additional super imposed load can the DT carry such that the resulting stress at the bottom fibers at mid-span is zero.

Structural Analysis
6th Edition
ISBN:9781337630931
Author:KASSIMALI, Aslam.
Publisher:KASSIMALI, Aslam.
Chapter2: Loads On Structures
Section: Chapter Questions
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1. The flooring of a warehouse is made up of double-tee joists (DT) as shown. The joists are
simply supported on a span of 7.5 m. and pre tensioned with one tendon in each stem with
an initial force of 745 kN each, located at 75 mm above the bottom fiber, loss of stress at
service load is 18%. Load imposed on the joists are:
Dead load = 2.3 kPa
Live load = 6 kPa
Properties of DT:
A = 200,000 mm²
yt = 88 mm
a = 2.4 m
I = 1880 x 106 mm4
yb = 267 mm
a=2.4 m
N.A.
75 mm
192 mm
88 mm
267 mm
a. Compute the stress at the bottom fibers of the DT at mid-span due to the initial pre
stressing force alone.
b. Compute the stress at the bottom fibers of the DT at mid-span due to the service loads and
pre stress force.
c. What additional super imposed load can the DT carry such that the resulting stress at the
bottom fibers at mid-span is zero.
Transcribed Image Text:1. The flooring of a warehouse is made up of double-tee joists (DT) as shown. The joists are simply supported on a span of 7.5 m. and pre tensioned with one tendon in each stem with an initial force of 745 kN each, located at 75 mm above the bottom fiber, loss of stress at service load is 18%. Load imposed on the joists are: Dead load = 2.3 kPa Live load = 6 kPa Properties of DT: A = 200,000 mm² yt = 88 mm a = 2.4 m I = 1880 x 106 mm4 yb = 267 mm a=2.4 m N.A. 75 mm 192 mm 88 mm 267 mm a. Compute the stress at the bottom fibers of the DT at mid-span due to the initial pre stressing force alone. b. Compute the stress at the bottom fibers of the DT at mid-span due to the service loads and pre stress force. c. What additional super imposed load can the DT carry such that the resulting stress at the bottom fibers at mid-span is zero.
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