27110 - steel - mahidolmucc.mahidol.ac.th/~egpcp/handout271/27110 - steel.pdf · – malleable...

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C O N S T R U C T I O N M A T E R I A L SI R O N & S T E E L

© 2010 | Praveen Chompreda | Mahidol University 2

O U T L I N E

• Introduction• Manufacturing of Steel• Properties of Steel• Steel Products for Construction• Joining of Steel• Durability of Steel

Guggenheim MuseumBiblao, Spain

Source: Wikipedia

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I R O N

• Iron is the 10th most abundant element in the universe• Iron accounts for about 35% of earth’s mass, most of it is in the inner core• Earth crust contains about 5% of iron, the 2nd most abundant metal (the

first being aluminum)

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I R O N

• The relatively low cost of iron and its high strength make it the most-used metal in the world. The majority of iron is in the form of steels, which are alloys of iron with different metals and carbon.

Akashi-Kaikyo Bridge, the world’s longest bridge, is made of steel

Source: Wikipedia Source: Wikipedia

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M A N U F A C T U R I N G O F S T E E LManufacturing of SteelIron Ore Pig Iron (Step 1)

Cast IronPig Iron Steel (Step II)

Steel AlloyForming of Steel (Step III)

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M A N U F A C T U R I N G O F S T E E L

• The manufacturing of steel consists of 3 main phases– Reducing Iron Ore to Pig Iron– Refining Pig Iron to Steel– Forming Steel into products

Iron Ore Pig Iron SteelSteel

ProductsBlast Furnace

Basic Oxygen Furnace, etc…

Blooming Mill

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M A N U F A C T U R I N G O F S T E E L

Source: Momlouk and Zaniewski (2006) 8

I R O N O R E P I G I R O N ( S T E P 1 )

• Iron does not occur in nature as pure metal, but as combinations with oxygen or sulfur, called Iron Ore. The most common are hematite (Fe2O3), magnetite (Fe3O4), or pyrite (FeS2)

• 3 main ingredients used in reducing Iron Ore to Pig Iron are Coke (product from Coal), Limestone, and Iron Ore

• Iron ore is converted to pig iron in the Blast Furnace

Hematite MagnetitePyrite (Fool’s Gold)Picture Source: Wikipedia

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I R O N O R E P I G I R O N

• Iron is extracted from ore by removing the oxygen, usually by combining with carbon to produce CO2

• It takes about 5-8 hours from the loading of material at the top till the iron is obtained at the bottom.

• The process is done continuously – the furnace never shuts down.

• To produce 1 ton of pig iron, it takes about 1300 kg of iron ore, 600 kg of coke, 400 kg of limestone, 7300 kg of air, 22000 kg of water, and 27x106 BTU of heat.

• Pig iron obtained from the blast furnace cannot be used by its own, due to its high carbon content (about 3.5-4%). It has to be processed further to reduce the amount of carbon and to remove other impurities.

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I R O N O R E P I G I R O N• Inside the blast furnace…

– The coke (from coal) reacts with oxygen to produce carbon monoxide (CO)

2 C + O2 2 CO

– Carbon monoxide reacts with iron ore to become carbon dioxide (CO2)

3 CO + Fe2O3 2 Fe + 3 CO2

– Limestone (CaCO3) is used as a flux (solvent) to help removing the impurities, such as silicon dioxide in the ore

CaCO3 CaO + CO2

CaO + SiO2 CaSiO3

– The molten slag is lighter than the molten iron, so it floats on the top and can be drawn off through an opening at the bottom of the furnace – this can later be used as cement replacement material in concrete (Recall GGBS = Ground Granulated Blast Furnace Slag)

Slag

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C A S T I R O N

• Cast iron is produced by reheating pig iron and remove some of the impurities. It contains about 2-4% of carbon

• It can be cast into molds

• It is brittle and best used in compression rather than tension

• Common applications are pipes and fittings.

• Cast iron is difficult to weld.

Source: Marotta (2005) 12

C A S T I R O N

• 4 main types– White cast iron: The carbon and iron

are in the form of iron carbide (Fe3C). It is hard and very brittle so it is not used as structural components. It may be used where high resistance to abrasion and wear is required. When broken, the fracture surface appears white.

– Grey Cast Iron: The carbon is present in the form of graphite flakes. This graphite make it softer and machineable, but it is still very brittle. When broken, the fracture surface appears grey. This is the most common type of cast iron.

Cast Iron Pipe Fittings

Source: wikipedia

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C A S T I R O N

– Ductile Iron or Spheroidal Graphite Iron: By adding some alloying elements and the right casting procedure, the graphite in the grey cast iron may be induced to form into spherulites (small spheres). This reduce the brittleness.

– Malleable Iron: By applying heat treatment to the white cast iron, the nodules of graphite may be formed. This helps increase the strength and reduce brittleness.

Coalbrookdale Iron Bridge (1785), UK Cast iron bridge Decorative Cast Iron Gate

Source: wikipedia Source: wikipedia

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P I G I R O N S T E E L ( S T E P 2 )

• Steel is an alloy of iron with some other metals, called alloying elements. Alloying elements are added to improve properties of iron such as hardness, elasticity, ductility, tensile strength, corrosion resistant, etc…

• Steel contains up to about 1.5% carbon• Structural Steel contains up to about 0.25% carbon• Types

– Mild Steel or Low Carbon Steel (C < 0.25%) this is the structural steel– Medium Carbon Steel or just Carbon Steel (0.3% < C < 0.6%)– High Carbon Steel (0.6% < C < 1.5%)– Alloy Steel (Steel + Alloying elements) eg. Stainless steel

• 3 main types of furnaces used in refining pig iron to steel– Open Hearth Furnace (Traditional)– Basic Oxygen Furnace (Most Popular)– Electric Arc

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P I G I R O N S T E E L

• Molten pig iron and recycled steel are dumped from the top.

• Pure oxygen is blown with high pressure into the furnace to stir things up and cause rapid burning of materials.

• Limestone is added as a flux• Impurities are either removed as gases

(such as CO2) or as slag.• Alloying metals may be added to

produce special steel alloy• Basic oxygen furnace can refine about

300 tons of steel in under 30 minutes. • The molten steel may be cast into a

large prism called Ingot to be sent to another factory to form into desired shapes

• Basic Oxygen Furnace

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P I G I R O N S T E E L

Molten pig iron is added to the top of the Basic Oxygen Furnace

Steel Ingot

Source: wikipediaSource: wikipedia

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S T E E L A L L O Y


S T E E L A L L O Y

Source: Momlouk and Zaniewski (2006)

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S T E E L

• The largest producer in the world is China, followed by Japan and USA

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S T E E L

• Today, most of the steel is from recycled steel. This has some effects on the chemical compositions of the modern steel by having elements that were not previously considered to be a part of normal steel chemistry

• It is now become more difficult to find a low-strength grade of steel. We tend to get much higher actual strength for the lower-strength grade of steel.

Source: wikipedia

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F O R M I N G O F S T E E L ( S T E P 3 )

• The steel ingot goes to blooming mill where it is reheated to about 1200 C and get passed through huge rollers to reduce the ingot to a smaller size

• It may take 20+ rollers to reduce the ingot into the desired shape and size• Typical shapes produced are plates, rods/bars, and structural steel rolled

shapes.

Source: wikipedia

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F O R M I N G O F S T E E L ( S T E P 3 )

Source: Illston and Domone (2001)

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P R O P E R T I E S O F S T E E LProperties of SteelTensile Test & Modulus of ElasticityImpact TestHardness Test

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P R O P E R T I E S O F S T E E L

• Properties of metals, in general, may be divided into 2 categories

– Structure Insensitive Properties : these are properties that has to do with the atoms themselves, but not the microstructure. Examples are density, elastic modulus, coefficient of thermal expansion, specific heat.

– Structure Sensitive Properties : these are properties that depends on the microstructure of the materials, which is greatly affected by heating and cooling histories. Examples are yield strength, fracture strength, ductility (elongation at failure), and fatigue performance.

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P R O P E R T I E S O F S T E E L

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T E N S I L E S T R E N G T H & M O D U L U S O F E L A S T I C I T Y

• Tensile strength (ASTM A 370) and modulus of elasticity of steel are obtained by testing a steel specimen under direct tension.

• We can record the load and the displacement between two points to get a stress-strain plot

Typical tensile test setup for large bars (left), and small bars/ wires (right)

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S T R E S S - S T R A I N C U R V E S• Typical stress-strain curve of mild steel in tension (we also assume that the

behavior in compression is the same as in tension – this is true for most purposes)

Source: ASCE (2001) 28

S T R E S S - S T R A I N C U R V E S

• The followings can be observed:

– The stress-strain curve is linear from the point of zero load to a point called Yield Point, Yield Strength (Fy), Limit of Proportionality, or Elastic Limit. In some steel, we can observe the upper yield point and the lower yield point.

– The slope of the stress-strain curve during the linear portion is called Modulus of Elasticity (E), the typically value is 200 GPa

– After the yield point, steel undergoes yielding, in which the strain increases significantly without much increase in the load

– At some point, the stress begin to increase until it reaches the point of maximum stress, called Ultimate Strength (Fu) at a strain much larger than the strain at yielding. This portion of the curve is called Strain Hardening Range.

– We usually grade the steel by its yield strength (not the ultimate strength as in concrete!)

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S T R E S S - S T R A I N C U R V E S– At the ultimate strength, the tensile test member exhibit “necking”

behavior in which the area of the test piece decreases as the deformation increases with the corresponding decrease in load. Thus, if we calculate the stress by Engineering Stress = F/Aoriginal, we get a decrease in stress from ultimate to rupture. But if we calculate the stress by True Stress = F/Aactual, we get an increase in stress (dashed line) instead.

Original

Just before Failure

At Ultimate

Necking

Source: Momlouk and Zaniewski (2006)

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– Note that if we unload the steel after the yield point, it will not return to the original length; thus, a permanent deformation has occurred

– If we reload it again, it will follow the unloading path until it reaches the previous maximum load. After that, it follows the same stress-strain curve as if it is loaded continuously (without unloading) to failure.

Source: ASCE (2001)

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• In the design of steel structures, we usually rely on the strength up to the yielding. For simplicity, we generally model the stress-strain curve as bilinear. We know that there is some reserved strength in the Strain Hardening rangebut we just don’t use it in the design.

Idealized Stress-Strain Curve

Source: ASCE (2001)

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• As the yield strength of steel increases (higher strength steel), the yield point becomes more difficult to define.

• We can define the yield point in this case by using Offset Method, or Proof Stress.

Yield point of A36 steel

Where should be the yield point???

Source: ASCE (2001)

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• We find the point of small strain (0.1%, 0.2% depending on the standard or the value agreed upon) and draw a line parallel to the linear portion of the stress-strain curve.

• The point where the parallel line intersects the stress-strain curve is the proof stress or the yield stress.

• We may also use the stress at 0.5% strain as the yield point. This may give slightly different yield point than the offset method.


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Source: ASCE (2001)

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I M P A C T• The Charpy V-Notch Impact test (ASTM

E23) is used to measure the energy required to fracture a steel specimen.

• It uses a hammer pendulum to strike a “notched” specimen

• After striking, some of the kinetic energy is absorbed by the test specimen so the swinging arm will not go up as high as its starting position. We can measure the height to compute the energy.

• The lower the energy required to fracture, the more brittle the steel

Notch

Source: Wikipedia Source: Wikipedia36

H A R D N E S S

• Hardness is the measure of the material’s resistance to small dent or scratch to the surface.

• Most common method is the Rockwell hardness test (ASTM E18)

• This method measures the penetration depth of small metal ball or diamond cone under a standard load.

• The hardness value can be used to estimate the tensile strength of the material. This is very useful because hardness test is easy to do, inexpensive, and do not require special specimens.

Source: Wikipedia

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F A C T O R S A F F E C T I N G S T R E N G T H

• For the same type of steel, the measured strength and/or elongation at failure may be affected by the following factors:– Loading rate (static vs. dynamic)– Location in the section where the sample is collected – this is usually

critical for hot-rolled sections as it is affected by “residual stress” in some parts of the section

– Loading history – cold-forming of steel changes the strength and deformation capacity of steel.

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• Structural steel sections have “residual stresses” in them.

• Residual stress occurs due to nonuniform cooling of the section after hot rolling. The thinner part cools faster than the thicker part.

• The parts that cool first will have residual compression. The parts that cool last will have residual tension.

• Magnitude and distribution depends on the shape of the section, not the strength of the steel.

• This reduce the usable strength to yielding

CompressionTension

Compression

Tension

Source: ASCE (2001)

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• Cold forming of steel (i.e. shaping of steel without heat) leaves the steel with higher yield strength but lower strain to failure.

• If we test the steel with the history of cold forming, we would get different behavior from the one without any forming

• Ductility = u/y

– u = ultimate strain

– y = yield strainSource: ASCE (2001) 40

S T E E L P R O D U C T S F O R C O N S T R U C T I O N SReinforcing steel

Round barDeformed barPrestressing strands

Structural steelHot Rolled steelCold-formed steelBuilt-up Members (Steel plate)

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S T E E L P R O D U C T S F O R C O N S T R U C T I O N S

• Reinforcing steel– Round bar– Deformed bar– Prestressing strands

• Structural steel– Hot Rolled steel– Cold-formed steel– Built-up Members (Steel plate)

Source: Wikipedia 42

R E I N F O R C I N G S T E E L

• Reinforcing bars are obtained by hot rolling of steel

• Two main types:– Round bar – the surface of the bar is

smooth– Deformed bar – the surface of the bar

has ribs on it

• The ribs on the surface of deformed bar increase the bond to the concrete. Thus, the Deformed bars are generally used as main reinforcement of structural members. Round bars are generally used as reinforcement to prevent concrete cracking under temperature changes and shrinkage.

Source: Wikipedia

Source: Wikipedia

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R E I N F O R C I N G S T E E L - G R A D E S

Type Grade Fy (ksc)Minimum

Fu (ksc)Minimum

Ultimate Strain (%) Minimum

Round Bar SR 24 2400 3900 21

Deformed Bar

SD 30 3000 4900 17

SD 40 4000 5700 15

SD 50 5000 6300 13

มอก. 20-2543, 24-2548

• Reinforcing steel is graded by the minimum yield strength

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R E I N F O R C I N G S T E E L - R O U N D B A R

Type Diameter (mm)

Cross-Sectional Area (mm2)

RB 6 6 28.3

RB 8 8 50.3

RB 9 9 63.6

RB 10 10 78.5

RB 12 12 113.1

RB 15 15 176.7

RB 19 19 283.5

RB 22 22 380.1

RB 25 25 490.9

RB 28 28 615.8

RB 34 34 907.9

มอก. 20-2543: เหล็กเสน้กลม

Grade: SR 24

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R E I N F O R C I N G S T E E L - D E F O R M E D B A RType Diameter

(mm)Cross-Sectional

Area (mm2)

DB 6 6 28.3

DB 8 8 50.3

DB 10 10 78.5

DB 12 12 113.1

DB 16 16 201.1

DB 20 20 314.2

DB 22 22 380.1

DB 25 25 490.9

DB 28 28 615.8

DB 32 32 804.2

DB 36 36 1017.9

DB 40 40 1256.6

มอก. 24-2548: เหล็กขอ้ออ้ย

Grades: SD 30, SD 40, SD 50

Source: Wikipedia

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R E I N F O R C I N G S T E E L - P R E S T R E S S I N G S T R A N D S

• Prestressing strands are made by twisting 2, 3, 7, or 19 wires together. The most common type is the 7-wire strand.

• They are made of higher strength steel than those used in regular reinforcing steel bars

• มอก. 420-2540: ลวดเหล็กกลา้ตเีกลยีวสําหรับคอนกรตีอดัแรง

Source: Naaman (2004)

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Source: Naaman (2004) 48


Prestressed concrete segmental girders

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S T R U C T U R A L S T E E L

• For steel structures, there are 3 main types of steel members– Hot rolled members – Cold-formed members– Built-up members (from steel plates)

Strata CenterMIT, Boston, MA

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S T R U C T U R A L S T E E L - H O T R O L L E D

• Hot rolled shapes are obtained by passing very hot block of steel through various rollers several times to obtain the desired shape.

• Most of the shapes are standardized by the American Institute of Steel Construction (AISC). Typical shapes are W or H (wide-flange), I, C (Channel), L (Angle), T, Pipe, and Tube.

• มอก 1227-2539: เหล็กโครงสรา้งรปูพรรณรดีรอ้น

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Source: Salmon and Johnson (1996) 52


• They are used for main structural members, such as truss members, beams, and columns.


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S T R U C T U R A L S T E E L - C O L D – F O R M E D

• Cold-formed shapes are obtained by stamping and/or bending steel plate to a desired shape at normal temperature

• Cold-formed sections usually have small thickness (we cannot bend a very thick plate). Common shapes are C (Channels), Z (Zees), and L (Angles)

Source: Salmon and Johnson (1996)

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• They are used mostly for nonstructural elements or for structures that carry small loads

Source: Wikipedia

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• มอก 1228-2537: เหล็กโครงสรา้งรปูพรรณขึน้รปูเย็น• Has only one grade: SSC 400

Yield StrengthMinimum (MPa)

Tensile StrengthMinimum (MPa)

Elongation, Minimum (%)

Thickness < 5 mm

Thickness > 5 mm

245 400-510 21 17

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S T R U C T U R A L S T E E L - B U I L T – U P M E M B E R S

• We can create structural members by welding steel plates into any desirable shapes

• Typical examples are bridge girders and columns of tall buildings

Source: Nowak (2004)

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S T R U C T U R A L S T E E L - B U I L T – U P M E M B E R S• มอก 1499-2541: เหล็กกลา้คารบ์อนรดีรอ้นแผน่มว้น แผน่แถบ แผน่หนา และแผน่บาง สําหรับงานโครงสรา้งเชือ่มประกอบ

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S T R U C T U R A L S T E E L - B U I L T – U P M E M B E R S

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J O I N I N G O F S T E E LRivetHigh-Strength BoltWelding

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J O I N I N G O F S T E E L

• Structural steel pieces may be join by one of these 3 methods:– Riveting– Bolting– Welding

Connection Details of the Coalbrookdale Iron Bridge(the first cast iron bridge)

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R I V E T

• Rivet is the oldest method of joining. It involves heating a small metal pin until it is sufficiently soft. The metal pin is inserted to the hole and a special tool is used to form the heads of the rivet

• Riveting is rather slow, requires a lot of skilled workers, cannot carry a lot of loads, and difficult to replace

• The method is now becomes obsolete due to the invention of high-strength bolts in the 1950s Source: Wikipedia

Source: Marotta (2005) 66

R I V E T

Rivets on columns and bridge truss members

Source: Wikipedia

Source: Wikipedia

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H I G H – S T R E N G T H B O L T

• High-strength bolt replaces rivet as a steel fastener

It takes about 4-5 highly skilled workers to install a rivet (not included in the picture are workers heating the rivet)

One worker can install a bolt

Construction of Empire State Tower, 1930

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• High-strength bolts are usually tightened such that high tensile stress is developed in the bolt. The tensile stress in the bolt causes compressive stress on the steel pieces being joined. The compressive stress causes friction to develop between the joined piece, holding the pieces together. There are two types of connections:– Slip Critical: The friction is high enough that the pieces must not slip past each

other under service load, i.e. the loads are transferred through friction only.– Bearing Type: The slippage is allowed under service load. The load is transferred

by bearing and shearing of bolts.Source: Salmon and Johnson (1996)

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W E L D I N G

• Welding is the joining of metal by applying heat to fuse the two pieces together

• The history of metal welding dates back to the Egyptian period (3000 B.C.). The modern welding method was invented around 1885. A lot of improvements to the process occurred during 1930-1950.

• There are several welding methods but the most popular are Arc Welding and Gas Welding– Arc welding uses an arc between the electrode and the grounded base

metal to heat both metals to their melting points. The electrode is coated with flux, which provide the oxygen-free atmosphere around the weld to prevent oxidation. The flux cools down to become slagcovering the weld area.

– Gas welding also uses an arc to heat the metal. However, it uses gas from external sources, such as inert gases or CO2, to shield the weld from oxidation. This is often used in small welds because there is no slag formation.

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W E L D I N G

Source: Momlouk and Zaniewski (2006)72

W E L D I N G

• Some types of structural steel are better than the others for welding, depending on its chemical composition

• Electrode must be selected to match the strength of the material being joined

• Diameter of the electrode must be selected to match the size of the weld and the electrical output of welding machine Source: Salmon and Johnson (1996)

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W E L D I N G

• Weld metal in arc welding is deposited by electromagnetic field, not gravity. Therefore, welding can be done in any positions.

• Welded connection are usually smaller and more aesthetically pleasing than bolted or riveted connections.


W E L D I N G

Source: Salmon and Johnston (1996)

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W E L D I N G

• The current practice is to weld parts of built-up structural members in the shop but using bolts to assemble the member in the field.– Field welding is inconvenient,

difficult to inspect, and can be expensive

– Shop welding is faster and looks better than bolting

Welds done in fabrication shop

Field Bolting

Field Bolting

Welded Plate Girder

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W E L D I N G

• Residual stress occurs in the welded section in a similar manner to the hot rolled sections: i.e. the parts that cool first will have residual compression. The parts that cool last will have residual tension.

Source: ASCE (2001)

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W E L D I N G• In addition, the location near the weld was subjected to very high heat and

fast cooling rate. A Martensite structure was developed, which was very hard and brittle. This is the area where failure often occurs. This area is called Heat Affected Zone (HAZ)

• To reduce the residual stresses and HAZ, cooling rate of welding must be carefully controlled, especially in large welds.


D U R A B I L I T Y O F S T E E LCorrosionPrevention of CorrosionWeathering SteelStainless Steel

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C O R R O S I O N

• Corrosion is a destruction of a material by electrochemical reaction. When the steel corrodes, rust is formed.

• Some rust on the steel reinforcement before placing of concrete is OK

• Rust on the steel structures must be avoided as it can lead to reduction in strength

• Steel rust at the rate of about 0.5mm/year• In order for rust to occur, we need 4 elements

– Anode: The electrode where corrosion occurs– Cathode: The other electrode needed to form a

corrosion cell– Conductor: A metallic pathway for electrons to flow– Electrolyte: A liquid that can support the flow of

electrons• Steel by itself already has 3 elements, it only needs

water (electrolyte) to complete the corrosion cell

Source: Nowak (2004)

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C O R R O S I O N

• Reactions:Anode Side Fe Fe2+ + 2e-

Fe2+ + 2(OH)- Fe(OH)2

Ferrous Hydroxide (Black Rust)4Fe(OH)2 + 2H2O + O2 4Fe(OH)3

Ferric Hydroxide (Red Rust)Cathode Side 4e- + 2H2O + O2 4(OH)-


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C O R R O S I O N

• The amount of time the steel stays wet affects the rate of corrosion.• Environmental contaminants may accelerate corrosion. Examples are SO2

in acid rain, and salts (from sea or deicing salts).

Corrosion of steel column near the sea Corrosion from deicing salts

Source: Nowak (2004) Source: Nowak (2004)Source: Nowak (2004)

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P R E V E N T I O N O F C O R R O S I O N

• Design the structure such that water cannot collect on the surface or joints


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• Design the structure such that inspection and maintenance can be done easily

Inspection Catwalk underneath a Cable-Stayed Bridge

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• Applying protective coating to seal off the surface from moisture.– The surface to be painted must be dry and clean– Periodic repainting is necessary

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P R E V E N T I O N O F C O R R O S I O N• Cathodic protection: we prevent the corrosion of steel by making it the

cathode side of the corrosion cell!– Sacrificial Anode: this is done by connecting more anodic metal with steel. The

anode metal will corrode instead of the steel. This anode metal must be replaced occasionally.

Source: Illston and Domone (2001) 86


– Anodic coating : this is similar to the sacrificial anode but, instead of using a piece of metal, the anode metals is coated on the surface of the steel.

• Galvanizing: uses Zinc to coat the surface of the steel

• Zinc-Pigmented Paint: Same concept as galvanizing but in the form of paint

Galvanized Surface

Aluminum anodes are mounted on steel structure

Source: Wikipedia

Source: Wikipedia

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– Impressed Current Cathodic Protection (ICCP): Using external power source to make the metal cathodic and consume the anode metal instead. Inert Anodes such as carbon, titanium, lead, or platinum are used. This is typically used for large structures, such as buried pipelines, as placing sacrificial anodes at regular intervals is impossible.

Source: www.daviddarling.info Source: www.byauto.com.cn

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W E A T H E R I N G S T E E L

• Weathering steel or high strength low-alloy (HSLA) steel (also known commercially as COR-TEN steel) is a steel alloy with very low percentage of carbon (<0.15%) and small amounts of chromium, copper, phosphorus, nickel, niobium, nitrogen, vanadium, molybdenum, silicon, or zirconium

• Weathering steel has the unique characteristic that, under proper conditions (not too wet and not too dry), it corrodes by forming a dense and tightly adherent oxide barrier that seals out the atmosphere and retards further corrosion. This is in contrast to other steels that form a coarse, porous and flaky oxide that allows the atmosphere to continue penetrating the steel.

• Although more expensive than the regular carbon steel, we save the cost of painting for the entire service life.

• ASTM A 242, ASTM A 572, and ASTM A 588

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W E A T H E R I N G S T E E L

U.S. Steel Building, Pittsburgh Core-Ten Sculpture

• It is widely used in bridges and marine structures.• It is not rust-proof. If water collects on the surface, it will corrode.


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S T A I N L E S S S T E E L

• Stainless steel, also known as high-alloy steels, contains 16-28% chromium, up to 22% nickel, and some manganese. It has very high resistance to corrosion due to the forming of a thin, transparent coating of chromium oxide over the surface.

• It is often used as kitchen tools, laboratory equipments, etc… For construction, stainless steel are used as cladding, water pipes/fittings, and corrosion-resistant reinforcement for concrete (ASTM A 955M).

• Over 150 grades are available, some has higher corrosion resistance than the others, some are harder, some has magnetic property, some are easier to weld, etc…

• Variety of finishes are available from unpolished, brushed, to mirror finishes.

Petronas TowersStainless steel cladding

Source: Wikipedia

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S T A I N L E S S S T E E L

St. Louis Gateway ArchSt. Louis, Missouri, USAStainless steel cladding

Chrysler Building, New York Stainless steel spireCompleted 1929Stainless steel rebar

Source: Wikipedia

Source: Wikipedia

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R E C A P

• Introduction• Manufacturing of Steel

– Iron Ore Pig Iron Steel• Microstructure & Heat Treatment• Properties of Steel

– Tensile Stress-Strain Curve– Impact & Hardness Test– Factors Affecting Strength

• Steel Products for Construction– Reinforcing steel

• Round Bar• Deformed Bar• Prestressing Strands

– Structural steel• Hot Rolled steel• Cold-formed steel• Built-up Members (Steel

plate)• Joining of Steel

– Riveting, Bolting, Welding• Durability of Steel

– Corrosion– Preventions of Corrosion– Weathering Steel– Stainless Steel

Source: Wikipedia

93

R E F E R E N C E S

• American Society of Civil Engineers (2001), Structural Steel Selection Considerations: A Guide for Students, Educators, Designers, and Builders, Ed. R. Bjorhovde et. al., ASCE, Reston, VA, 110 pages.

• American Society of Testing and Materials, ASTM A370, West Conshohocken, PA.• Illston, J. M. and Domone, P. L. J. (2001), Construction Materials: Their Nature and Behaviour, 3rd

Edition, Spon Press, London.• Mamlouk, M. S., and Zaniewski, J. P. (2006), Materials for Civil and Construction Engineers, 2nd

Edition, Prentice-Hall, NJ, 576 pages• Marotta, T. W. (2005), Basic Construction Materials, 7th Edition, Prentice-Hall, NJ, 598 pages• Naaman, A. E. (2004), Prestressed Concrete Analysis and Design: Fundamentals, Technopress 3000,

Ann Arbor, MI.• Nowak, A. S. (2004), Bridge Design Course Materials, University of Michigan, Ann Arbor.• Salmon, C. G. and Johnson, J. E. (1996), Steel Structures: Design and Behavior, 4th Edition,

HarperCollins College Publishers, NY, 1024 pages. • Smith, R.C, and Andres, C.K. (1989), Materials of Construction, 4th Edition, McGraw-Hill, 401 pages.• Thai Industrial Standard Institute, TISI 20-2543, Bangkok, Thailand• Thai Industrial Standard Institute, TISI 24-2548, Bangkok, Thailand• Thai Industrial Standard Institute, TISI 420-2540, Bangkok, Thailand• Thai Industrial Standard Institute, TISI 1227-2539, Bangkok, Thailand• Thai Industrial Standard Institute, TISI 1228-2537, Bangkok, Thailand• Thai Industrial Standard Institute, TISI 1499-2541, Bangkok, Thailand• http://www.wikipedia.org

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