1. Final Project - Materials - Metals Flashcards
Steel: how to protect steel against oxidation? (3)
- Paint 2. Galvanized 3. Chemically treated
Steel: characteristics?
Steel is characterized by:
- Strong resistance
- Stiffness
- Elasticity
What is the cheapest and strongest material?
Steel
Why should steel be protected to have fire resistance?
Although classified as an incombustible material, steel becomes ductile and loses strength when exposed to temperatures above 1000F (537C)
Steel: What do standards G40.20-F04 and G40.21-F04 define?
Provide requirements for various structural steels.
- General requirements for the manufacture of structural steels
- Steel Grades
- Chemical composition
- Mechanical characteristics
Steel: What is a grade?
Steel grades are designated by a number corresponding to the guaranteed minimum value of the elastic limit, followed by a letter identifying the type of steel.
The most frequently used structural steel grades are G40.21-300W for steel buildings and G40.21-350AT for bridges.
Steel: name the 7 types of steel & applications
- Type W: structural members
- Type WT: Bridges
- Type R: exterior coverings
- Type A: Welded constructions where low temperature toughness is not a selection criterion
- Type AT: Welded constructions where low temperature toughness is a criterion of choice
- Type Q: heavy plates and light structures of great resistance
- Type QT: high strength lightweight constructions (bridges, cranes) and for transport equipment
Advantages & disadvantages to steel construction
+ fast, precise construction
- fire coatings required
- corrosion resistance required
Which direction lateral forces are more critical in?
Short direction
(orient columns/ beams in this direction)
What is the span for beams (in a beam & girder system)?
20’ @ 32’
spacing 6’ @ 15’
beyond that, use web steel joists
Rule of thumb to estimate beam (W) depth & width?
Beams: Span / 20
Girders: Span /15
Width: 1/3 to 1/2 of the depth
What is the objective when selecting a W member?
Use the lightest steel section that will resist bending and shear forces within allowable limits of stress and without excessive deflection for intended use.
Define three types of steel framing connections:
- Moment Connections - Rigid Frame -
connections able to hold their original angle, by means of plates welded or bolted to the beam flanges & columns.
- Shear Connections - Simple Frame -
connections made to resist only shear and are free to rotate under gravity loads. Shear walls / diagonal bracing required.
- Semi-Rigid Connections - Semi-Rigid Frame -
connections have a limited but known moment-resisting capacity.
Types of steel frames:
Rigid frame: joints connecting column & beam are capable of resisting both forces & moments.
- Fixed frame:
rigid frame connected to supports with fixed joints. More resistant to deflection than hinged, but also more sensitive to support settlements and therman expansion and contraction
- Hinged frame:
rigid frame connected to its supports with pinned joints. Allows rotation as a unit (settlements or expansion/contraction)
- Three-hinged frame:
two rigid sections connected with pin joints. More sensitive to deflection, least affected by settlement or expansion mouvement.
Span ranges for light-gauge steel joists?
6” joists - 10’@14’
8” joists - 12’@18’
10” joists - 14’@22’
12” joists - 18’@26”
Rule of thumb to estimate joist depth: span/20
Spacing 16”, 24” or 48”
Strap bridging required 5’@8’
What members are required to prevent lateral movement of joist chords?
Horizontal or diagonal bridging
Spaced 10’@20’
Welded @ top & bottom chords
Resistance to lateral wind and seismic forces requires the use of:
shear planes, diagonal bracing, or rigid framing with moment-resisting connections
Estimating guides for steel columns:
4x4 tube
6x6 tube
W6x6
W8x8
W10x10
W12x12
W14x14
4x4 tube - 750 sq.ft. - grid 27’x27’
6x6 tube - 2400 sq.ft. - grid 49’x49’
W6x6 - 750 sq.ft. - grid 27’x27’
W8x8 - 3000 sq.ft. - grid 54’x54’
W10x10 - 4500 sq.ft. - grid 67’x67’
W12x12 - 6000 sq.ft. - grid 77’x77’
W14x14 - 12,000 sq.ft. - grid 109’x109’
Limiting height of steel studs:
3 5/8” - 12’
6” - 20’
8” - 28’
Rigid frames dimensions:
Spans : 30’@120’
Frames spaced at 20’@24’
Wall height @ bottom: 8’@30’
Pitch: 1:12 @ 4:12
Purlin spacing : 4’@5’
Max joist span
24x joist depth
Wide Flanges:
used for beams and columns (took the place of American Standard (aka I Beam) shapes)
3 standard series for open web steel joists
K- standard - 8”@30” deep - 12’ @ 60’ spans
LH - long span - 18”@48” deep - 28’@60’ spans
DLH - 52”@72” deep - up tp 144’ spans
Open Web Steel Joist
Lightweight, shop-fabricated steel members having a strussed web.
• Selected based on the span between bearing points, joist spain, slope, live/dead
loads, collateral loads, wind up lift, deflection criterial, and max depth allowed
- Spacing is commonly ranges from 2’ - 10’ on center : 4’ common
- May be supported by bearing wall or steel beams or joist girders
- Permit passage of mechanical services
- Work best for uniformly distributed loads
Angles:
Versatile, used for short beams supporting small loads (e.g.: as lintels)
Channels:
used with truss members and bracing as well as for short beams/lintels
Joist Girders
are beefier versions of joists designed to carry heavier loads…usually bays of the open web steel joists.
These bear on columns and structure.
Remember:
columns hold up steel beams or joist girders, which hold up joists, which hold up decking
Rivets:
Steel fasteners consisting of a cylindrical body and formed head that is brought to a a high heat inserted through holes matched in members to be joined and then worked with a special hammer to make another head on the other side.
- As it cools is shrinks and clamps the jointed pieces together
- Was originally the most used technique, but is very labor intensive compared to bolting and welding
Common bolts:
available, and installed for less than high-strength bolts. Used in joints where lower strength is sufficient enough to carry the load
• Act primarily in bearing and shear
High Strength Bolts:
Heat treated during manufacture to develop necessary strength
• Can get connecting ability from sheer resistance or from being tightened to the
point hat the members they join are kept from slipping by the friction between them (know as slip critical connections)
Welding:
Joints the members of a steel frame as if they were a monolithic whole, and connections are stronger than members they join in shear and moment force resistance.
- Welding and bolting can be combined in the same connection to take advantage of the unique qualities of each
- Required thickness/length of weld is determined by designer
What is the designation for the most commonly used structural steel for beams?
A36
A36 refers to the ASTM Standard A36/A36M, Standard Specification for Carbon Structural Steel
-Steel meeting this standard has a minimum yeld point of 36,000 psi
A153 steel is the standard for
hot dip zinc coating on iron and steel hardware
A441 steel is
a high strength strucutral steel used for welded construction
A501 steel is the designation for
hot formed welded and seamless carbon steel structural tubing
Which of the following is NOT a standard designation for open web steel joists
DLH
K
LH
ML
ML is not a designation
DLH - deep long span
K-standard open web joists
LH-long span joists
the depths in K series for steel joists range from
8 in - 30 in
(increase in increments of 2 in)
the depths in LH and DLH series for steel joists range from
28 in - 72 in
(increase in increments of 4 in)
The stringers of prefabricated steel utility stairs are normally constructed of
a. angle iron
b. channel sections
c. steel plate
d. tube sections
b. channel sections
american standard beams are known as…
S shapes
Describe the 3 types of metal structural connections.
1 - MOMENT (this sh*t is locked down)
• rigid frame
• connections hold original angle under loading of welded plates
2 - SHEAR
• simple frame
• connections resist shear loads only .: can rotate
3 - SEMI-RIGID
• semi-rigid frame
• assume limited but known moment resistance capacity
What is a good rule of thumb when estimating depth for beams and girders.
Beam = span/20 Girder = span/15
What is more structurally efficient an S (often called I) beam or a W beam
A W beam is a profile engineered to carry the load more efficiently.
What are the 2 basic types of steel?
1 - Structural Steel
• hot rolled
• strong
• versatile (1 storey up to towers)
2 - Lightweight Steel
• details sim. to wood frame
• low rise
• on-site erection = good for irregular shapes
What are the 2 types of open web steel joists?
STANDARD (K series )
• zigzag = single bent bar
• span = 4 - 18m : 13’-59’
• Bearing length = 100-150mm: 4”-6”
LONGSPAN (LH & DLH series)
• heavier web/chord members
• great for heavier loads + longer spans
• span = 8 - 18m : 26’-59’ (DLH can span up to 144’)
• Bearing length = 150-305mm: 6”12”
**compare:
24K9 = acceptable span 7-14m
24LH7 = acceptable span 11-14m
note: chord is larger on K series
How would you read the sizing for an open-web joist? example: 24K9
24K9
24” Depth of joist
K Joist series
9 Chord designation
Good rule of thumb for estimating open web steel joists.
SPAN should not exceed 24xs the JOIST DEPTH.
What size of overhang is acceptable for the K open web joist series?
5’-6” with an allowable load of 300 psf
Describe 3 most commonly used metal decking types.
FORM DECKING
• perm. formwork for reinforced conc. slab
COMPOSITE DECKING
• serves as tensile reinforcement for con. slab to which it is bonded with it’s ribs
CELLULAR DECKING
• weld flat sheet to underside of corrugated
=raceways for elec. + comms
* may also serve as acoustic ceiling if perf. flat sheet filled w glass fiber.
What must be done is metal decking is acting as a diaphragm, transferring lateral loads to shear walls.
MUST be welded to steel supports along entire perimeter.
What are the advantages (3) and disadvantage (1) of using lightgauge steel joists?
+ lighter/longer spans + more dim. stable than wood
+ easily cut/tooled onsite
+ prepunched holes for bridging/piping/wiring
- they conduct more heat than wood and have more embedded energy
Alloy:
a combination of pure metals to give greater strength or resistance to corrosion
Ferrous Alloy:
alloys that contain a lot of iron (e.g.: stainless steel, galvanized iron)
rolling
process of passing metal through rollers to produce the needed shape
- can be done while metal is hot or cold
- hot rolling eliminates flaws in the metal
- cold rolling inceases metal’s strength and elastic limit, but decreases ductility
Non Ferrous Alloys:
doesn’t contain much iron (e.g.: aluminum, copper, zinc)
Cast Iron:
hard brittle alloy of iron and 2.1 - 4% carbon that can be readily cast in a
mold, use for pipes, plumbing fixtures, hardware, castings, etc. (Crystal Place made of it)
Wrought Iron:
iron that has been purified by beating it repeatedly with a hammer, used
for ornamental work, grilles, pipes, and outdoor furniture (Eiffel Tower made of it)
Steel:
any range of alloys of iron and carbon that contain less than 2% carbon, the most
widely used structural metal in construction, used for framing, concrete, rebar, lathing,
conduit, pipes, fixtures, connectors like nails, bolts, and pins.
Aluminum:
Light weight metal with good thermal/electrical conductivity and resistance
to corrosion, used for lightweight framing, railings, grills, siding, curtain walls, doors/
windows, flashings, roofing, hardware, etc
Galvanic Corrosion:
an electrochemical process where one metal corrodes preferentially to another when they both are in electrical contact and immersed in an electrolyte (which is a liquid or gel that contains ions and can be decomposed by electrolysis)
Purpose of Galvanizing:
When metal is going to be used in an environment where corrosion is likely, it is often galvanized so that it will be able to withstand the conditions.
Galvanizing:
coating iron or steel with a protective layer of zinc by immersing it in a molten bath.
Anodizing:
process of coating aluminum with a protective oxide layer by an electrolytic process
galvanic series
The galvanic series determines the nobility of metals. When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience galvanic corrosion.
1- zinc
2- glavanized steel
3- aluminum
4- steel and iron
5- stainless steel
6- lead
7- tine
8- copper alloys (brass, bronze)
9- copper
As carbon is added to steel…
strength increases but ductility deacreases
Copper:
Metal that resists corrosion, electrical and thermal activity, used for electrical
work, water pipes, roofing/flashing, and mesh
Brass:
metal that resists corrosion, used for finish hardware, plumbing, HVAC
components and fittings
Lead:
Metal that resists corrosion and is workable, but also toxic, heavy, soft, and weak,
used for foundations, rough hardware, roofing and flashing
Zinc:
Metal used for roof coverings, flashings, and protective coatings for steel
Monel:
Metal used for roofing, flashing, countertops, sinks
Bessemer Process:
steelmaking procedure where carbon, silicon, and other impurities
are removed from iron to make steel.
Basic Oxygen Process:
steelmaking procedure where a hollow, water-cooled lance is
lowered into a container of molten iron/recycled steel scrap and a stream of pure oxygen
is blown in at high pressure from the lance to burn off the excess carbon/impurities.
Light Gauge Steel:
steel that is cold rolled and lighter than .018”
terneplate
an alloy of 75% lead and 25% tin used to plate steel for roofing
Galvanic Action or electrolysis occurs …
…when different metals are in contact and moisture is present.
- One metal corrodes as its ions are deposited onto the other metal
- When two metals are close to each other on the galvanic scale (right) they have a lessor tendency to corrode.
- Cathodes are stable metals not prone to corrosion
- Anodes are less stable and more likely to corrode
• So keep Cathodes and Anodes away from each other!! They don’t place nice.
Cathode and Anode diagram
Which type of brass finish would best prevent tarnish and require the least maintenance?
An organic finish woul best prevent tarnish and require the least maintenance
Anodized finished are used on what type of metal
aluminum
Which of the following is not a copper alloy?
a. austenitic stainless steel
b. monel metal
c. muntz metal
d. nickel silver
a. austenitic stainless steel
stainless steel is an alloy of iron, carbon, and chromium
austentic stainless steel is the most common type;also contains some nickel and/or manganese; nonmagnetic and not heat treatable
monel is a trade name for a metal alloy of…
copper and nickel
muntz metal is a common alloy of …
…60% copper and 40% tin
nickel silver is name given to an alloy of
65% copper, 25% zinc, and 10% nickel
Which of the following additives is NOT added to steel to improve corrosion resistance?
a. chromium
b. copper
c. tungsten
d. molybdenum
c. tungsten
tungsten is added to steel to improve the material’s ability to retain its strength when exposed to high temperatures
What are additives added to steel to improve its corrosion resistance?
chromium, copper, molybdenum, nickel
Wwo advantages of using a copper roof are its
workability
resistance to corrosion
disadvantages of copper roofing include
easily dented
expesnsive material for roofing
what percentage of carbon does structural steel typical contain
0.2%-0.5% ; considered medium carbon steel; most common
steel with over 2.0% carbon is classified as
cast iron
galvanic action can be avoided by…
…using neoprene spacers between dissimilar metals
Dissimilar metals should be physically separated by
nonconducting materials such as neoprene in order to prevent galvanic action
increasing the thickness of dissimilar metals will not prevent galvanic action; it will only prostpone complete deterioration
true or false.
Direct contact with water will speed up galvanic action
true
moisture in that air is enough to cause galvanic action
joining metals with heat and a filler metal with a melting point above 800 deg F is called
brazing
welding is joining two metals by heating them above…
their metling points
soldering is joining two metals with
lead based or tin based alloys as a filler metal that melt below 500 deg F
Oil canning is …
…a perceived waviness across the flat areas of sheet metal panels. It is a naturally-occurring phenomenon that is inherent in all light-gage sheet metal.
Oil canning is an aesthetic issue, not a structural problem or a defect.
in steel manufacturing what do manganese, molybdenum, vanadium, nickel and chromium do?
manganese - resistance to abrasion and impact
molybdenum - gives strength
vanadium - imparts strength and toughness
nickel and chromium - strength toughness and corrosion resistance
which of the following are characteristics of stainless steel?
a. it cannot be welded
b. it should not be in contact with copper
c. it is an alloy of steel and chromium
d. it is only available with mecahnical and coated finishes
e. it corrodes easily if exposed to oxygen
e. it is approximately as strong as bronze
B, C, D
which of the following types of metal should NOT be specified for connection hardware and flashing for use with wood treated with ACQ preservative?
a. aluminum
b. copper
c. stainless stell
d. hot dip galvanized
a. aluminum
ACQ (alkaline copper quat) is a wood preservative that contains up to 96% copper.
- it has taken the place of CCA (chromated copper arsenic)
- any metals used in proximity to ACQ treated wood must be compatible with copper according to the galvanic series
- aluminum flashing or connectors should never be used with treated lumber
- copper is the best choice, but while copper flashing is readily available, not all fasteners are made of copper
in the selection of exposed flashing, stainless steel doesn’t require additional protective coating, true or false
true
copper and stainless steel expand and contract at about the same rate.
true or false
true
Which is of the following door frame materials would provide the greatest durability at the lowest possible cost?
aluminum
hallow metal
stainless steel
wood
hallow metal
-wood frame would be least expensive but is not as durable as standard hallow metal (steel)
aluminium wondow are specified for installation in a masonry wall.
which material is the least desirable choice for flashing at the head of the window?
a aluminum
b. copper
c. stainless steel
d. lead
c. stainless steel
because of the metals listed, it is furthest from aluminum on the galvanic action table, even further than copper
Steel is defined as various iron based alloys w carbon content ____ than cast iron & ____ than wrought iron.
- *less than cast iron**
- *more than wrought iron**
Steel is incombustible but ductile and loses strength at temperatures over:
520 deg C
List 3 ways steel can be protected from oxidization
- painted
- galvanized
- treated
What are the 2 main types of steel?
Describe their properties.
1 - CARBON
- unalloyed
- residual elements controlled
**more carbon = less ductility/weldability
2 - ALLOY
- carbon steel w other elements added to obtain particular physical/chemical properties
What are these 4 types of steel composed of and what is their function?
1 - STAINLESS
2 - HIGH STRENGTH LOW ALLOY
3 - WEATHERING STEEL
4 - TUNGSTEN STEEL
1 - STAINLESS (min. 12% chromium)
= highly resist. to corrosion
2 - HIGH STRENGTH LOW ALLOY
• low carbon w <2% alloy
= high strength/ductility + low corrosion
3 - WEATHERING STEEL
• forms an oxide coating when exposed to rain/moisture
= protects from further corrosion
4 - TUNGSTEN STEEL
• contains 10-20% tungsten
= increased hardness + heat retention
There are Ferrous metals other than steel, describe just 2 of them:
1 - Cast Iron
2 - Wrought Iron
1 - CAST IRON
• hard • brittle • cast in sand • ornamental
2 - WROUGHT IRON
• soft = readily forged & welded
List 3 main NONferrous metals.
*nonferrous = metals containing no iron
1 - Aluminum
2 - Copper
3 - Brass
What are the advantages (4) of Aluminum and largely how is it used?
1 - Ductile
2 - Malleable
3 - Light
4 - Natural Corrosion resistance (can be improved by anodizing)
Wide use as 2nd building elements:
• windows
• door frames
• flashing
• trim
What MUST always be separate from aluminum and why?
Other metals and alkaline matter:
• wet concrete
• mortar
• plaster
To prevent GALVANIC ACTION!
What are the advantages(4) of Copper and largely how is it used?
1 - Ductile
2 - Malleable
3 - Resistance to corrosion (roofing/flashing)
Wide Use:
• roofing/flashing
• wiring
• piping
• manufacture of alloys (bronze/brass)
What is GALVANIC ACTION?
Occurs between 2 dissimilar metals if enough moisture for electric current to flow.
• tends to corrode the more noble metal and plate the least noble:
Corrode Noble
(gold, titanium, stainless, bronze)
Plate Least Noble
(Zinc, Aluminum, Cast Iron, Nickel)
Why does galvanizing occur?
- Galvanization occurs when two metals are in the presence of a sufficiently pronounced humidity for an electric current to circulate.
- This electric current corrodes one metal and causes a deposit to appear on the other.
Explain the Galvanic Series
- Presents the metals classified from the most noble to the least noble.
- Noble metals (eg gold or silver) resist corrosion.
- Of 2 metals, the one that is lowest in the list corrodes when the humidity is high enough for an electric current to flow.
- The greater the distance between two metals in the galvanic series, the more the less noble of the two will be subject to corrosion
Galvanic series: examples of noble and less noble metals?
From most noble to least noble:
- Gold, platinum
- Titanium
- Silver
- Stainless steel
- Bronze
- Copper
- Brass
- Nickel
- Pewter
- Lead
- Melting
- Soft steel
- Aluminum, 2024 T4
- Cadmium
- Aluminum, 1100
- Zinc
- Magnesium
