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STRCTENG 201 > Steel > Flashcards

Steel Flashcards

1
Q

Advantages of steel:
High (?)
(?) Stable
Can form (?)
No (?) and (?)
Relatively (?) to fabricate
Easy to (?)
(?) weight

A

High strength
Dimensionally stable
Can form complex shapes
No creep and shrinkage
Relatively cheap to fabricate
Easy to erect
Light weight

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2
Q

Advantages of Timber
(?) resource
(?) to handle on site
(?) stable in fire
good (?) appeal
can form (?)
(?) appearance
(?) weight
high (?) to (?) ratio

A

Renewable resource
Easy to handle on site
Dimensionally stable in fire
Good aesthetic appeal
Can form complex shapes
Warm appearance
Light weight
High strength to weight ratio

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3
Q

Advantages of combined systems
Can have a finished appearance of (?)
Can carry (?) and (?) load
High (?) resistance
easy to (?)
good (?) resistance
Care needed for good (?) and (?) design
(?) weight
Excellent (?)
can form (?) shapes

A

Can have a finished appearance of timber
Can carry concentrated and heavy long-term compression load
High seismic resistance
easy to erect
good fire resistance
Care needed for good acoustic and thermal design
light weight
Excellent appearance
can form complex shapes

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4
Q

what frame comprises of beams and columns and in a severe earthquake, beams or connections yield first and columns yield last?
_____________
|_____|_____|
|_____|_____|
|_____|_____|
|………|………|

A

Moment resisting frame

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5
Q

what frame comprises of collector beams, braces and columns and in a severe earthquake, braces are the first item to buckle or yield and columns yield last?
_________
|___/\__|
|___/\__|
|/……….|

What are each of the members called?

A

concentrically braced frame
____ collector beam
/\ brace

column

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6
Q

what frame comprises active links, beams braces and columns and in a severe earthquake, active links yield first and columns yield last?
_________
|/—–_|
|/—–_|
|_/—–_|
|/……….|
What are each of the members called?

A

Eccentrically braced frame
____ beam
—- active link (beam)
| column
/\ braces

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7
Q

What are the four different types of open cross sections?

A

I : i section
C : c section or channel section
⊥ : tee section
L : angle section

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8
Q

what are the three types of closed cross sections?

A

RHS: rectangular hollow section
SHS: Structural hollow section or square hollow section
CHS: circular hollow section

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9
Q

Flange width =

A

bf or B

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10
Q

beam depth =

A

d or D or h

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11
Q

flange thickness =

A

tf or T

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12
Q

Web thickness =

A

tw or t

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13
Q

d1 = web clear depth

A

d - tf, top - tf, bottom

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14
Q

b = flange clear width

A

(bf - tw) / 2

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15
Q

manufacturer stage 1
- (?) and (?) mixed at 1600C
- (?) reaction gives (?) iron
- (?) contains up to (?) carbon and other elements
- excess (?) bottles for (?) use
- (?) cogenerated from (?) and (?) making process: (?) of total used for NZ (?)

A
  • iron ore and carbon mixed at 1600C
  • reduction reaction gives pic iron
  • pig iron contains up to 5% carbon and other elements
  • excess CO2 bottles for industrial use
  • electricity cogenerated from iron and steel making process: 60% of total used for NZ steel
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16
Q

manufacture stage 2
- (?) is pushed through (?) iron to (?) most of the (?), then
- excess (?) is removed by adding (?) and (?)
- killed (?) = all (?) removed
- (?) steel then (?) into final shape
- (?) rolling

A
  • oxygen is pushed through pig iron to remove most of the carbon, then
  • excess oxygen is removed by adding aluminium and silicon
  • killed steel = all oxygen removed
  • molten steel then rolled into final shape
  • controlled rolling
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17
Q

what are killed steels

A

steels with all oxygen removed

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18
Q

what are the benefits of killed steel

A

it has the finest grain structure and good toughness

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19
Q

what does controlled rolling do to steel

A
  • reduces grain size
  • increases impact toughness, ductility, through thickness toughness
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20
Q

what are the mechanical properties dependent on

A

rolling direction

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21
Q

what does increased rolling increase and have no change in

A

yield stress and tensile strength
no change in elastic modulus

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22
Q

what are the three basic categories of hot rolled sections

A

beams, columns, and piles

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23
Q

what happens to beams after hot rolled

A

d (depth) ≈ 2 to 3 times b (width) and tf (flange) / tw (web) ≈ 1.5

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24
Q

what happens to columns after hot rolled

A

d ≈ b and tf/tw ≈ 1.5

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25
Q

what happens to piles after hot rolled

A

d ≈ b and tf/tw ≈ 1.0

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26
Q

are webs or flanges stronger after rolling?

A

webs due to the extra rolling of the webs

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27
Q

what does hot rolling do to sections

A

optimise second moment of area = keep material away from neutral axis to optimise the bend resistance of the specific section

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28
Q

how to weld sections together and how much energy required

A

manufactured by welding of hot-rolled plate
an energy intensive process

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29
Q

what is the trend to reduce overall cost of manufacturing

A

increase welded section range and reduce hot-rolled section range

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30
Q

what are the two principal elements of steel

A

iron and carbon

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31
Q

what is the carbon content for structural steels?

A

< 0.8%

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32
Q

what is the maximum carbon content for any steel

A

< 3%

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33
Q

what increases with increasing strain rate

A

yield force

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34
Q

for what is impact loading up to 100% increase

A

blast

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35
Q

300W, 350W =

A

structural low carbon steels

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36
Q

480W =

A

high strength, low alloy steel

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37
Q

700Q =

A

quenched and tempered steel

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38
Q

what is the same for all types of steel

A

the modulus of elasticity E

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39
Q

what happens when steel crystallises

A

it forms grains around the initial points of solidification

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40
Q

what exerts a major influence on the mechanical properties of steel

A

grain size

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41
Q

what size grain is good

A

small

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42
Q

what are the benefits of small grain sizes
- distributes (?) finely through (?)
- increases (?)
- decreases (?)
- improves (?)
- increases (?) properties (slightly)

A
  • distributes inclusions finely through steel matrix
  • increases fracture toughness
  • decreases hardenability (tendency to become hard and brittle during fabrication)
  • improves heat treatability
  • increases mechanical properties (slightly)
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43
Q

fully killed steel are fine grained because of

A

the influence of aluminium or silicon

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44
Q

what kind of thermal or mechanical treatment reduces grain size

A

controlled rolling

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45
Q

what causes residual stresses in steel members

A
  • uneven cooling or hot rolled sections
  • cutting of edges
  • welding of pieces together
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46
Q

why are residual stresses not very important in design?

A
  1. they are always in internal equilibrium
  2. their influence on fracture initiation is slight in static conditions and is allowed for in fatigue design
  3. their influence on design capacity is allowed for in the design of members for compression and bending
  4. they do not show up in the historical record as causing problems
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47
Q

what materials can achieve plastic flow at normal temperatures

A

Fe3+ and Al3+

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48
Q

what structure do metals exist as

A

a space lattice

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49
Q

what can a space lattice be visualised as

A

a series of continuous spaced metal atoms (ions). An electron cloud occupies the spaces in the lattice

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50
Q

what can space lattices be depicted as

A

linked ‘unit cells’

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51
Q

what is the smallest volume element of a space lattice

A

unit cell

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52
Q

when a metal is stressed below the elastic limit

A

it returns to the original dimension

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53
Q

what is the target region for design structures for in service condition

A

stressed below elastic limit

54
Q

when a metal is stressed above the elastic limit

A

permanent deformation remains

55
Q

what is the target region for design of structures for the ultimate limit state condition

A

stressed above elastic limit

56
Q

what body centered cubic materials below 900c are harder to deform than face centered cubic materials

A

tungsten and iron

57
Q

why are BCC materials harder to deform than FCC materials

A

because there are fewer active slip systems

58
Q

FCC materials are very easy to deform due to

A

12 possible slip systems

59
Q

what are FCC materials

A

silver, gold, copper, aluminium and steel above 900c

60
Q

as deformation occurs

A

individual grains elongate in the direction of flow

61
Q

where is work that is not dissipated as heat stored

A

as internal energy in the crystal

62
Q

with distortion greatest on the slip planes and grain boundaries, what is the result

A

the result is an increased resistance to further deformation called strain or work hardening

63
Q

strain ageing
- steel initially (?) into (?) range (eg by earthquake)
- then (?) of (?) elapses
- Then another (?) into the (?) range
the second time around, steel may show (?) and (?)
- this is due to effects of (?) permitting (?) atoms eg (?) and (?) to lock up (?) and is called (?)
- addition of (?) fixes free (?) into (?) and greatly reduces (?)
- fully (?) typically not (?) if (?) or (?) strain <5%, so in well designed and detailed structures, it only applies to (?) elements and even then not (?).
- can be an (?) with (?)

A
  • steel initially strained into inelastic range (eg by earthquake)
  • then period of time elapses
  • Then another loading event into the inelastic range
    the second time around, steel may show high yield strength and lower ductility
  • this is due to effects of heat permitting interstitial atoms eg C and N to lock up dislocations and is called strain ageing
  • addition of aluminium fixes free nitrogen into aluminium nitride and greatly reduces susceptibility
  • fully killed low carbon steels typically not susceptible if axial or shear strain <5%, so in well designed and detailed structures, it only applies to designated yielding elements and even then not significant.
  • can be an issue with older steels
64
Q

what is characterized by tearing of metal and significant plastic deformation

A

ductile fracture

65
Q

what appearance does ductile fracture have

A

gray, fiberous appearance

66
Q

what are ductile fractures associated with

A

overload of structure or large discontinuities

67
Q

what is characterized by rapid crack propagation without significant plastic deformation

A

brittle fracture

68
Q

what appearance does brittle fracture have

A

bright granular appearance

69
Q

what brittle fracture types are generally present

A

flat type and chevron patterns

70
Q

what are static loads

A

loads applied slowly

71
Q

what do static loads cause

A

minimal dynamic effects in the structure (eg fatigue failure)

72
Q

are static loads constant or non constant

A

constant, (its day to day variation is less than around 10% of the maximum design value)

73
Q

what loads are considered static loads

A

building loads

74
Q

what are dynamic loads (repeated loads)

A

a fluctuating load that changes in magnitude over time

75
Q

what are types of dynamic loads (repeated loads)

A

trucks, trains, people, conveyor systems, cranes, furniture, warehouse material, snow, water

76
Q

what is fatigue

A

deterioration of a material under repeated cycles of stress or/and strain, resulting in progressive cracking and fracture

77
Q

what are the most significant fatigues

A

large number of cycles at small strains or stresses

78
Q

what percentage of steel failures are fatigue failures

A

80-90%

79
Q

what part of a frame are particularely susceptible to fatigue

A

joints

80
Q

where are fatigue failure most likely to occur

A

wind induced loading of structures such as tall signs and other flexible structures

81
Q

what are transition temperatures

A

temperatures at which the fracture behaviour changes from ductile to brittle

82
Q

within the transition zone, you get

A

50% ductile and 50% brittle fracture

83
Q

what occurs in susceptible metals when these metals are below the transition temperature

A

brittle failure at low temperatures

84
Q

what are the two common strengths of structural bolts

A

4.6 = mild steel
8.8 = high strength structural

85
Q

what bolt is most common in steel to steel connections

A

8.8 high strength structural bolt

86
Q

what bold is used in steel to concrete hold down connections

A

both bolts

87
Q

for property class 4.6 bolt, what is its mode

A

snug tight mode, designated /s

88
Q

what does snug tight mode do

A

allows bolts to slip into bearing in service
rotation can occur in service

89
Q

for property class 8.8 bolt, what is its mode

A

snug tight mode, designated /s
fully tensioned mode, designated /t

90
Q

what does fully tensioned mode do

A

bolts plastically stretched when tightened
very high clamping forces
joints rigid under normal operating conditions

91
Q

what are the types of welds

A

fillet welds
incomplete penetration butt weld
complete penetration but tweld

92
Q

what are fillet welds based on

A

ultimate shear failure through DTT

93
Q

what are weaker than members connected

A

welds

94
Q

what is the cheapest weld to produce

A

fillet welds

95
Q

what types of fillet weld performs well in static and earthquake loading

A

double sided fillet weld and complete penetration butt weld

96
Q

what welding is not so good in fatigue loading

A

fillet weld

97
Q

what is good about incomplete penetration butt weld

A

good for plate to plate connection where full strength connection is not required

98
Q

what is always weaker than plates being connected

A

incomplete penetration butt weld

99
Q

what weld has poor performance in fatigue

A

incomplete penetration butt weld

100
Q

what welding has no ductility capability

A

incomplete penetration butt weld

101
Q

what is the most expensive weld to make

A

complete penetration butt weld

102
Q

what does complete penetration butt weld do

A

develops full strength of the weakest member being connected

103
Q

what type of welding is best for fatigue loading

A

complete penetration butt weld

104
Q

what types of bolts used to hold down concrete

A

property class 4.6 or 8.8 (8.8 more common)

105
Q

what are the three types of connections

A
  • simple (rotate under design actions without moment)
  • semi-rigit (carry moment but weaker than beams)
  • rigid (no rotation under design actions)
106
Q

what does web plate connection carry

A

vertical loading

107
Q

what are the failure modes of web plate connection

A

in-plane yielding and bolt hole elongation

108
Q

what are suppressed in the web plate connections

A

bolt and weld failure is supressed

109
Q

what connection has very limited axial load capacity

A

web plate connection

110
Q

what connection has high rotation and tension pull-in capacity

A

web plate connection

111
Q

what connection has no design moment capacity

A

web plate connection

112
Q

what connection carries vertical loading

A

flexible end plate connectionwh

113
Q

what type of failure mode occurs with flexible end plate connection

A

plane bending

114
Q

what are suppressed in the flexible end plate connections

A

bolt and weld failure

115
Q

what connection has reasonable compression capacity

A

flexible end plate connection

116
Q

what connection has high rotation and tension pull-in capacity

A

flexible end plate connection

117
Q

what connection has no design moment capacity

A

flexible end plate connection

118
Q

what is an example of semi rigid connection

A

flange bolted joint

119
Q

what defines moment in flange bolted joint

A

rigid elastic behavior

120
Q

what connection can rotate inelastically

A

flange bolted joint

121
Q

what connection can accommodate low rotation with no visible damage or need to reinstatement

A

flange bolted joint

122
Q

what connection can accommodate high rotation with flange plate fracture

A

flange bolted joint

123
Q

what are examples of rigid connection

A

bolted moment end plate + beam moment-resisting splice

124
Q

what connection can be designed to be weaker or stronger than the beam

A

bolted moment end plate

125
Q

what is the failure mode of bolted moment end plate

A

by endplate and or column flange out of plane bending

126
Q

what are suppressed in bolted moment end plate connection

A

bolt or weld failure

127
Q

what connection can have complex load paths and design procedure

A

bolted moment end plate

128
Q

what connection performs very well in earthquakes

A

bolted moment end plate

129
Q

what does flanges resist in beam moment-resisting splice

A

moment-induced and direct axial forces

130
Q

what does web resist in beam moment-resisting splice

A

shear and moment due to eccentric shear transfer

131
Q

what are suppressed in beam moment-resisting splice

A

bolt and weld failure

STRCTENG 201 (3 decks)

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