facts Flashcards

1
Q

reactions for pin

A

2

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2
Q

reactions for roller

A

1

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3
Q

reactions for fixed end

A

3

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4
Q

Point moments will show up in ________ but not in _______ diagrams.

A

bending moment, shear force

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5
Q

What is the sign convention of sagging?

A

positive

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6
Q

What is the sign convention of hogging?

A

Negative

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7
Q

A beam is subjected to sagging. Where is the compression and tension?

A

tension on bottom of curve, compression on top of curve

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8
Q

What is the bending moment at an internal support e.g. pin?

A

0

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9
Q

Where will the point of zero shear be?

A

at the maximum bending moment

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10
Q

How do point loads and moments represent themselves in shear force and bending diagrams?

A

PL: vertical shift in SF, cause change in BM
PM: vertical shift in BM, not present in SF

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11
Q

What 3 things should be checked for after completing a SF and BM diagram?

A

reference co-ordinate system, value labels, dimensions

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12
Q

What should always be the first step in approaching a problem?

A

Verifying determinancy

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13
Q

Describe the changes in fibre length to the sections below when a beam is subjected to a bending moment
a. neutral axis
b. tension fibres
c. compressive fibres

A

a. no change
b. elongate
c. shorten

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14
Q

What are 4 major assumptions of truss analysis?

A

The members only connect at the nodes
Members have negligible weight
The pins (at the nodes) are frictionless
The loads are only present at the nodes

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15
Q

What is the sign convention for tensile stress/ strains vs compressive stresses/ strains?

A

tensile = +ve, compressive = -ve

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16
Q

What two methods would be used to locate POCs?

A

similar triangles or polynomials/ polynomial solving

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17
Q

The area under the SF diagram is equal to ______. Hence it can also be said that the BM is the result of __________ the SF diagram.

A

the change in bending moment, integrating

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18
Q

If the SF diagram is first order, what order will the BM be?

A

second

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19
Q

The SF diagram is linear, what will the BM diagram look like?

A

third order curve

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20
Q

How should internal support calculations be approached?

A

deduce as much information as possible about reactions and then split the element into two parts along the pin

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21
Q

List the 3 most common types of external supports

A

roller, pin, fixed end

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22
Q

list the 2 most common types of internal support

A

roller, pin

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23
Q

what order line does a UDL produce?

A

2nd order (linear)

24
Q

what order line does a point load produce?

A

1st order, parallel lines with vertical shifts

25
How do you locate a POC?
Take moments about the point using an unknown variable x from the distance and let this moment = 0
26
How do you find the location of a point of zero shear?
equate forces either side of point to zero and solve for the unknown distance (usually occurs in UDLs)
27
What units are moment of inertia in?
mm^4 or m^4
28
If in doubt about units for length, force or large prefixes: _____________________.
Revert to SI units e.g. metres, newtons and other non-prefixed terms BE CAREFUL with squared units (e.g. square the power of 10 you are changing by too)
29
How many values of z are there for a section?
2 (assuming the top and bottom parts are different - divided at the neutral axis)
30
Should you choose the minimum and or maximum z value in subsequent calculations stress/ moment capacity calculations?
minimum
31
To include a point moment in calculations, does it need to be multiplied by the distance from the point being analysed?
No
32
When drawing Bending moment diagrams of 3rd order (and upwards), how should the concavity be determined?
Positively if sagging and negatively for hogging as a starting point also consider if gradient of shear force/ bending moment should be 0 or not
33
Tensile stresses and strains are _____ since they cause elongation. Likewise _______________ are ___________.
positive, compressive stresses and strains, negatige since they shorten
34
How many members (maximum) can be cut in the method of sections?
3
35
What are the 4 different types of failure under tension?
Brittle (direct split), Shear (diagonal split), ductile cup and cone (extruded section of smaller diameter stretched) and complete ductile (pulled into two "triangle" shaped 3D sections
36
A greater moment if inertia or second moment of area along one axis than the other indicates _________.
The section will be more resistant to bending along that axis
37
Safe deflection is ____ than ______ .
less, 1/250 span
38
What are the two loading states?
Ultimate limit and serviceability limit
39
what is the difference between the two limit states
ultimate limit state - safeguards structural failure serviceability limit state - verifying actual loading
40
list factors affecting deflection
span to depth ratio support types member material support/ connection material areas of tensions and compression/ reinforcement
41
what are the 3 deflection calculation methods
successive integration McCauley's method Moment-Area method
42
List the values that can be calculated relating to bending in the respective order
deflection slope bending moment shear force load
43
what are boundary conditions in the successive integration method
distance x along beam and deflection at the supports
44
what is the sign conventions for slope angles
1st/3rd quadrant = positive 2nd/4th quadrant = negative
45
dy/dx = ________ in deflection analysis
slope
46
y = ______ in deflection analysis
deflection
47
d^2 y / d x^2 = _________ in deflection analysis
bending moment
48
the units used to measure slope are _________.
degrees, an angle
49
how can deflection be reduced
increasing E and I reinforcements (increasing flexural rigidity)
50
when the slope function is equated 0, the deflection is at a __________.
Maximum
51
list the 4 stages of failure
localised failure damage spreading' loss of structural integrity complete collapse
52
permanent actions for floorboard design
self-weight of joists self-weight of floorboards
53
A C16 beam indicated ________.
allowable stress/ strength = 16N/mm^2
54
in a stress distribution diagram, compression is drawn to the ____ and tension to the ______.
right, left
55
in stress distribution diagrams, compression is negative. true of false?
true
56
unit of slope using integration of moment function
radians - remember to check units and convert where necessary