Steel Flashcards by Reian Dunning

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

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

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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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

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

Moment resisting frame

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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?

concentrically braced frame
____ collector beam
/\ brace

column

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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?

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

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What are the four different types of open cross sections?

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

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what are the three types of closed cross sections?

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

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Flange width =

bf or B

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beam depth =

d or D or h

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flange thickness =

tf or T

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Web thickness =

tw or t

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d1 = web clear depth

d - tf, top - tf, bottom

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b = flange clear width

(bf - tw) / 2

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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 (?)

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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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

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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what are killed steels

steels with all oxygen removed

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what are the benefits of killed steel

it has the finest grain structure and good toughness

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what does controlled rolling do to steel

reduces grain size
increases impact toughness, ductility, through thickness toughness

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what are the mechanical properties dependent on

rolling direction

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what does increased rolling increase and have no change in

yield stress and tensile strength
no change in elastic modulus

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what are the three basic categories of hot rolled sections

beams, columns, and piles

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what happens to beams after hot rolled

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

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what happens to columns after hot rolled

d ≈ b and tf/tw ≈ 1.5

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what happens to piles after hot rolled

d ≈ b and tf/tw ≈ 1.0

are webs or flanges stronger after rolling?

webs due to the extra rolling of the webs

what does hot rolling do to sections

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

how to weld sections together and how much energy required

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

what is the trend to reduce overall cost of manufacturing

increase welded section range and reduce hot-rolled section range

what are the two principal elements of steel

iron and carbon

what is the carbon content for structural steels?

< 0.8%

what is the maximum carbon content for any steel

< 3%

what increases with increasing strain rate

yield force

for what is impact loading up to 100% increase

blast

300W, 350W =

structural low carbon steels

480W =

high strength, low alloy steel

700Q =

quenched and tempered steel

what is the same for all types of steel

the modulus of elasticity E

what happens when steel crystallises

it forms grains around the initial points of solidification

what exerts a major influence on the mechanical properties of steel

grain size

what size grain is good

small

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

- 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)

fully killed steel are fine grained because of

the influence of aluminium or silicon

what kind of thermal or mechanical treatment reduces grain size

controlled rolling

what causes residual stresses in steel members

- uneven cooling or hot rolled sections - cutting of edges - welding of pieces together

why are residual stresses not very important in design?

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

what materials can achieve plastic flow at normal temperatures

Fe3+ and Al3+

what structure do metals exist as

a space lattice

what can a space lattice be visualised as

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

what can space lattices be depicted as

linked 'unit cells'

what is the smallest volume element of a space lattice

unit cell

when a metal is stressed below the elastic limit

it returns to the original dimension

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

stressed below elastic limit

when a metal is stressed above the elastic limit

permanent deformation remains

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

stressed above elastic limit

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

tungsten and iron

why are BCC materials harder to deform than FCC materials

because there are fewer active slip systems

FCC materials are very easy to deform due to

12 possible slip systems

what are FCC materials

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

as deformation occurs

individual grains elongate in the direction of flow

where is work that is not dissipated as heat stored

as internal energy in the crystal

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

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

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 (?)

- 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

what is characterized by tearing of metal and significant plastic deformation

ductile fracture

what appearance does ductile fracture have

gray, fiberous appearance

what are ductile fractures associated with

overload of structure or large discontinuities

what is characterized by rapid crack propagation without significant plastic deformation

brittle fracture

what appearance does brittle fracture have

bright granular appearance

what brittle fracture types are generally present

flat type and chevron patterns

what are static loads

loads applied slowly

what do static loads cause

minimal dynamic effects in the structure (eg fatigue failure)

are static loads constant or non constant

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

what loads are considered static loads

building loads

what are dynamic loads (repeated loads)

a fluctuating load that changes in magnitude over time

what are types of dynamic loads (repeated loads)

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

what is fatigue

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

what are the most significant fatigues

large number of cycles at small strains or stresses

what percentage of steel failures are fatigue failures

80-90%

what part of a frame are particularely susceptible to fatigue

joints

where are fatigue failure most likely to occur

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

what are transition temperatures

temperatures at which the fracture behaviour changes from ductile to brittle

within the transition zone, you get

50% ductile and 50% brittle fracture

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

brittle failure at low temperatures

what are the two common strengths of structural bolts

4.6 = mild steel 8.8 = high strength structural

what bolt is most common in steel to steel connections

8.8 high strength structural bolt

what bold is used in steel to concrete hold down connections

both bolts

for property class 4.6 bolt, what is its mode

snug tight mode, designated /s

what does snug tight mode do

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

for property class 8.8 bolt, what is its mode

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

what does fully tensioned mode do

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

what are the types of welds

fillet welds incomplete penetration butt weld complete penetration but tweld

what are fillet welds based on

ultimate shear failure through DTT

what are weaker than members connected

welds

what is the cheapest weld to produce

fillet welds

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

double sided fillet weld and complete penetration butt weld

what welding is not so good in fatigue loading

fillet weld

what is good about incomplete penetration butt weld

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

what is always weaker than plates being connected

incomplete penetration butt weld

what weld has poor performance in fatigue

incomplete penetration butt weld

what welding has no ductility capability

incomplete penetration butt weld

what is the most expensive weld to make

complete penetration butt weld

what does complete penetration butt weld do

develops full strength of the weakest member being connected

what type of welding is best for fatigue loading

complete penetration butt weld

what types of bolts used to hold down concrete

property class 4.6 or 8.8 (8.8 more common)

what are the three types of connections

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

what does web plate connection carry

vertical loading

what are the failure modes of web plate connection

in-plane yielding and bolt hole elongation

what are suppressed in the web plate connections

bolt and weld failure is supressed

what connection has very limited axial load capacity

web plate connection

what connection has high rotation and tension pull-in capacity

web plate connection

what connection has no design moment capacity

web plate connection

what connection carries vertical loading

flexible end plate connectionwh

what type of failure mode occurs with flexible end plate connection

plane bending

what are suppressed in the flexible end plate connections

bolt and weld failure

what connection has reasonable compression capacity

flexible end plate connection

what connection has high rotation and tension pull-in capacity

flexible end plate connection

what connection has no design moment capacity

flexible end plate connection

what is an example of semi rigid connection

flange bolted joint

what defines moment in flange bolted joint

rigid elastic behavior

what connection can rotate inelastically

flange bolted joint

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

flange bolted joint

what connection can accommodate high rotation with flange plate fracture

flange bolted joint

what are examples of rigid connection

bolted moment end plate + beam moment-resisting splice

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

bolted moment end plate

what is the failure mode of bolted moment end plate

by endplate and or column flange out of plane bending

what are suppressed in bolted moment end plate connection

bolt or weld failure

what connection can have complex load paths and design procedure

bolted moment end plate

what connection performs very well in earthquakes

bolted moment end plate

what does flanges resist in beam moment-resisting splice

moment-induced and direct axial forces

what does web resist in beam moment-resisting splice

shear and moment due to eccentric shear transfer

what are suppressed in beam moment-resisting splice

bolt and weld failure