MECHANICS OF MATERIALS
11th Edition
ISBN: 9780137605521
Author: HIBBELER
Publisher: RENT PEARS
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PROBLEM 2.50
1.8 m
The concrete post (E-25 GPa and a
=
9.9 x 10°/°C) is reinforced with six
steel bars, each of 22-mm diameter (E, = 200 GPa and a, = 11.7 x 10°/°C).
Determine the normal stresses induced in the steel and in the concrete by a
temperature rise of 35°C.
6c
"
0.391 MPa
240 mm
240 mm
6₁ =
-9.47 MPa
For some viscoelastic polymers that are subjected to stress relaxation tests, the stress decays with
time according to
a(t) = a(0) exp(-4)
(15.10)
where σ(t) and o(0) represent the time-dependent and initial (i.e., time = 0) stresses, respectively, and t and T denote
elapsed time and the relaxation time, respectively; T is a time-independent constant characteristic of the material. A
specimen of a viscoelastic polymer whose stress relaxation obeys Equation 15.10 was suddenly pulled in tension to
a measured strain of 0.5; the stress necessary to maintain this constant strain was measured as a function of time.
Determine E (10) for this material if the initial stress level was 3.5 MPa (500 psi), which dropped to 0.5 MPa (70
psi) after 30 s.
For the flows in Examples 11.1 and 11.2, calculate the magnitudes of the Δ V2 / 2 terms omitted in B.E., and compare these with the magnitude of the ℱ terms.
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