Civil Engineering Reference
In-Depth Information
The steel has a modulus of elasticity equal to 200,000 MPa and a co-
efficient of thermal expansion equal to
a. What is the length of shrinkage?
b. What tension load is needed to return the length to the original
value of 4 meters?
c. What is the longitudinal strain under this load?
1.28 Estimate the tensile strength required to prevent cracking in a con-
crete-like material that is cast into a bar, 50 in. long, and is fully re-
strained at each end against axial movement. The concrete is
initially cast and cured at a temperature of 100°F and subsequently
cools to a temperature of 0°F. Assume the modulus of elasticity is 5
million psi and the thermal coefficient is
1.29 State two examples in which corrosion plays an important role in
selecting the material to be used in a structure.
1.30 Briefly discuss the variability of construction materials. Define the
terms accuracy and precision when tests on materials are per-
formed.
1.31 In order to evaluate the properties of a material, samples are taken
and tested. What are the two most important factors that must be
satisfied when the sample is collected? Show how these factors can
be satisfied.
1.32 A contractor claims that the mean compressive strength for a con-
crete mix is 32.4 MPa (4700 psi) and that it has a standard deviation
of 2.8 MPa (400 psi). If you break 16 cylinders and obtain a mean
compressive strength of 30.3 MPa (4400 psi), would you believe the
contractor's claim? Why? (
Hint:
Use statistical
t
-test.)
1.33 During construction of the surface layer of asphalt pavement, two
samples were taken every day to measure the asphalt content in the
mix to ensue that it is within the specification limits. The target
value was set at 5.5 percent with a tolerance of
10
-5
m/m/°C.
1.1
*
10
-6
in./in./°F.
5
*
; 0.4 percent.
The
following asphalt content data were collected:
Date
Asphalt Content, %
Date
Asphalt Content, %
May 5
5.7
May 12
5.3
May 5
5.8
May 12
5.6
May 6
5.3
May 13
5.8
May 6
5.4
May 13
5.1
May 7
5.7
May 14
5.8
May 7
5.7
May 14
5.9
May 8
5.6
May 15
5.1
May 8
5.8
May 15
6.2
May 9
5.4
May 16
5.2
May 9
5.5
May 16
4.8
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