Set 8-3

Mill Test Certificates

Chemical{ Samples are taken from the molten metal{ Chemical analysis is performed { reported on a mill test certificate for an individual

heat or batch of steel{ Heat is usually 50 to 300 tons of steel

Physical{ Samples from finished product (as required by a

specific steel standard){ tensile yield (Fy), tensile strength (Fult), and tensile

elongation tests are done{ Reported on mill test certificate

Classification and Standards for Steels

Classifications:{ classification system are generally based on

composition{ most common is SAE-AISI system; other is UNS

First two digits identify primary alloy type (e.g. 10 for carbon, 13 for manganese)

last two digits for carbon content

Standards are generally based on performance{ e.g. ASTM, AMS, ASME,

Steel Products in Civil Engineering

Plate Steel (for welded beams) Shapes (wide flange, I-beams, channels, tees) Fasteners Reinforcing for Concrete

{ Reinforcing steel (rebar){ Prestressing tendon{ Postensioning tendon and bar

Sheet steel (cladding, light steel framing, decks, roofs

700-950550-700Heat treated for high strength, generally weldable (if special procedures used) and good toughness

High strength quenched and tempered steel

480 (typ)350 (typ)Weathering steel low carbon steel with alloying elements giving some corrosion resistance

Atmospheric corrosion resistant steel

450-550300-480low carbon, strength comes from other alloys such as vanadium and columbium

High strength low alloy steel

480-550350-400

Higher carbon which increases strength but reduces ductility, toughness, and weldability; less common e.g. electrical transmission towers where connections are bolted and members are small

High Strength carbon steel

380-450245-300common grade, C and Mn are main strengthening elementsCarbon Steel

Fu(MPa)

Fy(MPa)

DescriptionType

Typical general categories of structural steel

Structural Steel Grades in Canada

Quench and tempered low alloy, notch tough, steel plateType QT

Quench and tempered low alloy steel plateType Q

atmospheric corrosion-resistant, weldable, notch toughType AT

atmospheric corrosion-resistant, weldableType A

atmospheric corrosion-resistantType R

weldable, notch toughType WT

weldableType W

DescriptionCode

CSA G40.21 specifies grades of steel with letter and number:{ e.g. Grade 300W is a designation for steel with fy =

300 MPa (see standard for exceptions) where the letter designation means one of the following:

Most common

(Canadian G.41)

Structural Shapes

Hot steel passed through series of rollers to make various shapes

From Mamlouk and Zaniewski

Beijing Olympic Stadium Birds Nest designed by Herzog and DeMeuron, and Arupuses high strength low alloy plate steel (110 mm thick; Chinese grade Q460)

Structural Steel for Bridges

CSA S6 Canadian Highway Bridge Design Code: { Structural Steel: CAN/CSA-G40.21

Normal: (Type W??) Weathering Steel: Type A atmospheric corrosion-resistant steel Fracture Critical: Type AT, WT or QT

{ Cast Steel: ASTM 27M or ASTM 148M or ASTM A486M{ Stainless Steel ASTM A167{ Bolts: ASTM A325M, A490M{ Cables

Bright wire: ASTM A510 Galvanized wire: ASTM A641 Bridge strand: ASTM A586 Wire Rope: ASTM 603

{ High Strength Bars: CSA G279

Other Approximate Properties of Structural Steel

appox 11.7 x 10-6 /C(varies greatly for different steel types)

Coefficient of Thermal Expansion

7850 kg/m3Density

0.30Poissons Ratio

200,000 MPaElastic Modulus

Weathering Steel

Develops a dense tightly adhered coat of rust that inhibits further corrosion (more or less)

Requires no paint for most environments Can still result in rust stains onto concrete piers etc e.g. WRB bridge in Kelowna (steel is painted near the

expansion joints only) e.g. in cladding is the Civil Rusty Hut Example types of Weathering Steel

{ Canada CSA G40.20 Grades 350A and 350R{ US ASTM A242, ASTM A588 (check){ UK BS 4360

Certification of Companies for Fusion Welding of Steel Structures

- 3 divisions of certification- Owner/designer should specify the appropriate division (e.g. buildings and bridges Div 1 or Div 2.1)

CSA W47.1

Cold Formed Steel Structural MembersCSA-S136

General Requirements for Rolled or Welded Structural Quality Steel/Structural Quality Steel

CSA-G40.20/G40.21

Welded Steel Construction (Metal Arc Welding)CSA-W59

Canadian Highway Bridge Design CodeCAN/CSA-S6

Limit States Design of Steel StructuresCSA-S16-01

TitleCode Designation

Examples of Canadian Codes

Examples of British Steels

BS 2763 fult appox 1700 MPaSteel Wire

Cold reduced, hot rolledBS 1449.1 (production standard)BS 2989/EN 10142 galvanized formed steel

Grades: Z28 (fy = 280 MPa)Z35 (fy = 350 MPa)

Cladding

BS 4360 or EN 10025{Grade 43 (fy = 275 MPa){Grade 50 (fy = 335 MPa)

Buildings mostly Grade 43 although columns and composite beams in multi-story are often Grade 50

Grade 50 common in bridges

Notch toughness: -5 C buildings internal-15 C buildings external-15/-25 C bridges

(depending on location)Weather resistant BS 4360

Plate and Rolled Steel

Fastener Products

Conventional bolts, twist-off type tension control bolt assemblies, nuts, washers, compressible-washer-type direct tension

indicators, anchor rods, threaded rods, forged steel structural hardware

Reinforcing Steel (rebar)

Geometry:{ Bars (wire rolls for small sizes and straight

bar) Plain (smooth round) now not common Deformed (bumps on surface)

{ Most commonly used reinforcing for structural concrete

{ Wire Mesh (sheets or rolls) Plain and deformed (deformed not common)

{ Used in some structural concrete but more common as crack control in non-structural concrete

Rebar Specifications

CSA A23.1:{ CSA-G30.18

{ ASTM A82/A82M-07 Standard Specification for Steel Wire, Plain, for Concrete Reinforcement{ ASTM A496/A496M-07 Standard Specification for Steel Wire, Deformed, for Concrete Reinforcement

{ ASTM A184/A184M-06 Standard Specification for Fabricated Deformed Steel Bar Mats for Concrete Reinforcement

{ ASTM A185/A185M-07 Standard Specification for Steel Welded Wire Reinforcement, Plain, for Concrete

{ ASTM A497/A497M-07 Standard Specification for Steel Welded Wire Reinforcement, Deformed, for Concrete

{ ASTM A704/A704M-06 Standard Specification for Welded Steel Plain Bar or Rod Mats for Concrete Reinforcement

{ ASTM A775/A775M-07 Standard Specification for Epoxy-Coated Steel Reinforcing Bars

Types of Rebar in CSA S6 and MOTH BC

Billet steel bars 300R, 400R, 500R, 400W, 500WG30.18Welded steel wire fabric; Welded deformed steel wire fabricG30.5 and G30.14Cold-drawn steel wire; Deformed steel wireG30.3 and G30.14

Rebar Sizes

19.625

11.775

7.850

5.495

3.925

2.355

1.570

0.785

Nominal Linear Mass(kg/m)

(confirm these)

YY55M

YY45M

YY35M

YY30M

YY25M

YY20M

YYY15M

YYY10M

400R, 400W, 500W

300R

Epoxy Coated Bars

Uncoated Bars(CSA Grades)

Bar Designati

on

ASTM A615/A615M-07 Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete

1.1 This specification covers deformed and plain carbon-steel bars for concrete reinforcement in cut lengths and coils. Steel bars containing alloy additions, such as with the AISI and SAE series of alloy steels, are permitted if the resulting product meets all the other requirements of this specification. The standard sizes and dimensions of deformed bars and their number designations are given in Table 1 . The text of this specification references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables) shall not be considered as requirements of the specification. 1.2 Bars are of three minimum yield strength levels: namely, 40000 [280 MPa], 60000 [420 MPa], and 75000 psi [520 MPa], designated as Grade 40 [280], Grade 60 [420], and Grade 75 [520], respectively.

Reinforcing Steel for Chloride Environments

Epoxy coated reinforcing steel{ ASTM A-775M and D-3963M from certified plants{ care not to damage coating{ gives about extra 20 years protection { was common in 80s and 90s

Galvanized Rebar{ ASTM A-767M Class 1 or CSA G164{ Not too common in Canada but do have good track record in

some locations Fiber Reinforced Polymer (FRP)

{ Typically glass or carbon composites{ excellent new products{ See Chapter 16 of Canadian Highway Bridge Design Code

and CSA S806

Reinforcing Steel for Chloride Environments

Regular steel with other protection measures such as combinations of:{ Increased concrete cover,{ Corrosion inhibitors,{ Better crack control, (curing practice, pre-stressing

or post tension, fibers, rebar detailing){ Low permeability to chlorides (silica fume, fly ash,

slag, low w/cm){ Coatings, { cathodic, protection

e.g. good cover, corrosion inhibitors, silica fume, fly ash, low w/cm used on Golden Ears

Wire, Strand, Cable

Higher carbon contents Individual wire is cold drawn from hot rolled to 90% reduction

which produces a heavily worked structure Dislocation network provides high strength Wires wound together to make a strand (typically 7 wire strand but

also 19, and 37) Strands wound together to make cables

Prestressed Concrete Tendons

ASTM A416/A416M-06 Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete{ Two types: low-relaxation (most common) and stress relieved{ Two grades: 1725MPa and 1860 MPa ultimate tensile strength{ 0.5 and 0.6 mm average diameter

ASTM A421/A421M-05 Standard Specification for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete{ Two types: BA button anchorage and WA wedge anchorage

ASTM A722/A722M-07 Standard Specification for Uncoated High-Strength Steel Bars for Prestressing Concrete{ Min 1035 MPa{ Plain (Type I) and Deformed (Type II)

CSA S6 references CSA G279

Post-Tensioning

Fully bonded (grouted) or unbonded(greased and inside plastic sheath)

Usually 7 wire strand to:{ ASTM A416, A421, A722

Note: corrosion of unbonded tendons has been a problem in the past and special care is need during manufacture and installation

Wire for Cables in Suspension Bridges

Example of Properties:{ High quality (close control on composition)

e.g.

{ Galvanized{ High strength (e.g. tensile strength =1550 MPa{ Elongation (e.g. 4% in 250 mm){ Coating elongation (e.g. no peel on 1.5x wire diameter mandrel){ Wire size: 4.88 (more common) and 4.11 mm dia{ Supplied in large diameter rolls (e.g. 1.5m) to prevent coating failure

and to facilitate spinning on site{ Wires can be pre-assembled into strands at factory then made into

cables (or run parallel) on site

0.15-0.30Silicon

Fire and Steel

Fire and Steel do no mix steel softens quickly and looses strength, leaving little life safety for egress

Fire protection is stipulated in buidling codes (not structural standards) such as:{ Vancouver Building By-law{ BC Building Code

Amount of protection depends on:{ Type of Occupancy e.g. school, home, warehouse{ Size of structure

Protection over fire resistant insulation may be required

Corrosion of Steels

Destructive action or deterioration of metal by sometimes chemical but mostly electrochemical reaction with the environment

Corrosion Environments: { atmosphere{ aqueous solutions{ soils{ acids and bases{ inorganic solvents{ sea water (deicing salts) etc{ high temperature

Electrochemical Corrosion Process

corrosion cells are formed with a continuous flow of electrons

Cathode and Anode reactions corrosion requires:{ source of water{ source of oxygen{ electrical continuity{ potential difference

Types of Corrosion

general corrosion (rusting) Pitting corrosion galvanic corrosion stress-corrosion crevice corrosion hydrogen intergranular biological filliform

case of dissimilar metals

Fe has a higher electromotive potential than Cu

if Fe replaced with Zn electrons would flow opposite direction

Case of Reinforced Concrete

high pH (caused by OH-) results in passive layer on surface of steel, therefore does not rust

HOWEVER: chloride can disrupt passive layer and cause corrosion or carbonation can lower pH and cause corrosion

Corrosion Control

1. Protective paint coatings paint becomes a barrier between steel and atmosphere

2. Hot Dip Galvanizing steel immersed in bath of molten zinc resulting in: Zn corrodes preferentially over the iron

(sacrificial anode) acts as a barrier as well

Corrosion Control

3. Cathodic Protection:{ impressed current will reverse potential and

reaction does not occur4. Use corrosion resistant metal:

stainless steel weathering steels

5. In the case of reinforced concrete replace steel with FRP materials glass, aramid, carbon in a polymeric matrix very brittle polymer can be vinyl ester or epoxy

Galvanic Series

materials higher in the chart will corrode before those lower

Uniform Corrosion

General loss of material exposed to corrosion environment

General thinning takes place until failure

Galvanic Corrosion

corrosion due to electrical contact of two dissimilar conductive materials

Pitting Corrosion

Pitting corrosion is a localized form of corrosion by which cavities or "holes" are produced in the material.

Pitting is considered to be more dangerous than uniform corrosion damage because it is more difficult to detect, predict and design against.

A small, narrow pit with minimal overall metal loss can lead to the failure of an entire engineering system.

Example of Corrosion Pits

Intergranular Corrosion

loss of material at grain boundary

Hydrogen Embrittlement

cracking, blistering and premature failure of a material due to the entry of hydrogen into the material causing brittleness

Crevice Corrosion

Crevice corrosion is a localized form of corrosion usually associated with a stagnant between metals in close contact

Such stagnant microenvironments tend to occur in crevices (shielded areas) such:{ under gaskets, washers, disbonded coatings, threads, lap

joints and clamps etc.

Crevice corrosion

Crevice corrosion is initiated by changes in local chemistry within the crevice: { Depletion of inhibitor in the crevice { Depletion of oxygen in the crevice { A shift to acid conditions in the crevice { Build-up of aggressive ion species (e.g.

chloride) in the crevice

Stress corrosion cracking

Stress corrosion cracking (SCC) is the cracking induced from the combined influence of tensile stress and a corrosive environment.

BCE Place, Toronto, Ontario