Stress and Strain TUTORIAL 6 to answer just click on the button or image related to the answer.
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Stress and Strain
TUTORIAL 6
to answer just click on the button or image related to the answer
what is stress?
Question 1a
internal force intensitya
force per unit area c
internal force b
a or c d
what are the units of stress?
Question 1b
kN, MNa
kPa, MPa c
kN / m, MN /m b
kNm2, MNm2d
what is strain?
Question 2a
a bad back achea
change in size or shapec
response to stress b
b and d e
change in size or shape relative to original stated
b and c f
what are the units of strain?
Question 2b
mm, cm, ma
no units c
kN / m b
kNmd
what is the strain in the cable?
Question 3a
4 mma
8 x 10-4 b
50 kN
5 m
20 mm
a 20mm ø high-strength steel cable 5 m long has a weight of 50 kN at its end. Neglecting the self-weight of the cable andGiven that the cable lengthens by 4mm
8 x 10-4 mmc
what is the stress in the cable?
Question 3b
159.2 kPaa
159.2 MPab
50 kN
5 m
20 mm
a 20mm ø high-strength steel cable 5 m long has a weight of 50 kN at its end. Neglecting the self-weight of the cable andGiven that the cable lengthens by 4mm
0.15 kPac
is the cable strong enough?
Question 3c
noa
yesb
50 kN
5 m
20 mm
a 20mm ø high-strength steel cable 5 m long has a weight of 50 kN at its end. Neglecting the self-weight of the cable andGiven that the cable lengthens by 4mm
Given that the maximum allowable tensile stressfor high-strength steel is 1000 MPa
what factors do we have to take Into consideration?
Question 4a
strength of the columna
slenderness of the columnb
when a column is under load
a and bc
what is the first means of failurewe should check for?
Question 4b
column breaking under compressiona
bucklingb
when a column is under load
what is the stress in the column?
Question 5a
1 MPaa
4 kPa b
a reinforced concrete column , 400 x 400 mm and 3.5 m high is subject to a load of 160 kN
Given that the column shortens by 0.07 mm
1 kPac
160 kN
3.5
m
400 mm
what is the strain in the column?
Question 5b
50a
2 x 10-5 b
a reinforced concrete column , 400 x 400 mm and 3.5 m high is subject to a load of 160 kN
Given that the column shortens by 0.07 mm
0.00002 mmc
160 kN
3.5
m
400 mm
is the column strong enough?
Question 5c
yesa
no b
a reinforced concrete column , 400 x 400 mm and 3.5 m high is subject to a load of 160 kN
Given that the column shortens by 0.07 mm
Given that the maximum allowable stressfor the concrete is 20 MPa
160 kN
3.5
m
400 mm
could you reduce the area of the column?
Question 5d
yesa
no b
a reinforced concrete column , 400 x 400 mm and 3.5 m high is subject to a load of 160 kN
Given that the column shortens by 0.07 mm
Given that the column is understressed
160 kN
3.5
m
400 mm
maybe c
to what size could you theoreticallyreduce the area of the column?
Question 5e
90 mm x 90 mma
400 mm x 200 mm b
a reinforced concrete column , 400 x 400 mm and 3.5 m high is subject to a load of 160 kN
Given that the column shortens by 0.07 mm
160 kN
3.5
m
400 mm
200 mm x 40 mm c
what would be the problem with that?
Question 5f
nonea
it would buckle b
Given that you want to reduce the column to 90 mm x 90mm
160 kN
3.5
m
400 mm
it would be difficult to build c
b and c d
next question
enough !
f = F /A – so it’s force distributed over an areathat means it’s the intensity of the force, not the force itself
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partly correct
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a thousand times NO! a force is a force – not stress
next question
enough !
f = F /A – so it’s force distributed over an area
1 kN/m2 = 1 kPa
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that’s force units
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go back to the formulaf = F / A
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enough !
strain is a response to stress andis a relative concept
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No?Then you are the pain
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I don’t like that
the change is just the deformation – not the strain
next question
enough !
length over length means strain is dimensionless
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e = ΔL / L
this is length over length
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where’s the force in e = ΔL / L ?
next question
enough !
0.0008 is also correct but 8 x 10-4 gives a better feel
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e = ΔL / L
what’s ΔL, what’s L, what are the units for strain?
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what are the units for strain ?
next question
enough !
Well done !
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f = F / A
check your calculations and units(it’s good practice to keep everything to Newtons and
mm
1 N/mm2 = 1 MPa = 1MN/m2)
next question
enough !
actual stress of 159 MPa is much less than max allowable stress of 1000 MPa
and then think again
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What’s the actual stress? What’s the maximum allowable stress?
Is the actual stress less or more than the max allowable stress?
next question
enough !
both are important
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next question
enough !
we always check to see if a column is slenderand would buckle first
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next question
enough !
Right on ! f = F / A
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How did you get that?f = F / A
What’s the force? What’s the area?
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check your calculations and your units?It’s good practice to keep everything to Newtons and
mms
1 N/mm2 = 1 MPa = 1 MN/m2
next question
enough !
0.00002 is also correct but 2 x 10-5 is easier to follow
Check your calculations? What’s ΔL? What’s L?
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e = ΔL / L
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What are the units of strain ??
e = ΔL / L
next question
enough !
actual stress of 1 MPa is much less than max allowable stress of 20 MPa
What’s the actual stress? What’s the maximum allowable stress?Is the actual stress less than or greater than the max allowable stress?
SO ?
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next question
enough !
it depends on how much we reduce it by
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If it’s understressed that means the area is greater than needs be
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next question
enough !
according to calculationsA = F / f
Minimum required area = 8000 mm2
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not according to the theoretical calculations
f = F / A A = F / f
the end !
Yes it’s much too slender. It would buckle immediately
Also, how could you pour concrete into such a small area?
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think again !
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