Steel Lecture No.1

Ferrous or Non-ferrous

Metals are classified as either ferrous or non-ferrous.

• Ferrous metals are those containing a substantial proportion of iron, such as stainless steel and galvanized iron

• Non-ferrous metals are all the others, such as aluminum, copper, and zinc.

Ferrous Metals

• The principle constituent of all ferrous metals is iron, which is the second most abundant metal and fourth most abundant element of earth.

Non-ferrous Metals

• Almost all non-ferrous metals share one desirable characteristic; they resist corrosion and generally have excellent workability.

• As with iron and steel, almost all non-ferrous metals used in construction are alloys.

It is common today to talk about 'the iron and steel industry' as if it were a single thing; it is today, but historically they were separate products.

Steel is a metal alloy whose major component is iron, with less than 2% carbon content. Carbon is the most cost effective alloying material for iron, but many other alloying elements are also used. Carbon and other elements act as a hardening agents.

Steel with increased carbon content can be made harder and stronger than iron, but is also more brittle. Alloys with higher carbon content higher than 2% are known as cast iron.

Varying the amount of alloying elements and their distribution in the steel controls qualities such as the hardness, elasticity, ductility, and tensile strength.

Increased tensile strength, hence very economical for tension members, or even columns restricted in dimensions due to architectural considerations.

Elastic modulus of these steels is not increased by the added elements, hence their use for beams is justified only when deflection (sag) is not a controlling factor.

Cast iron usually refers to grey any of a group of iron-based alloys containing more than 2% carbon.

It is made by remelting iron, often along with substantial quantities of scrap iron and scrap steel, and taking various steps to remove undesirable contaminants such as phosphorus and sulfur. Carbon and silicon content are reduced to the desired levels, which may be anywhere from 2% to 3.5% for carbon and 1% to 3% for silicon depending on the application. Other elements are then added to the melt before the final form is produced by casting. Iron is most commonly melted in blast furnace. After melting is complete, the molten iron is removed or ladled from the hearth of the blast furnace. This process is thought to have been devised by the late 18th century ironmaster John Wilkinson, whose innovative ideas revolutionized the field of metallurgy.

Crystal Palace Joseph Praxton

London 1851

cast iron and glass

Wrought iron is commercially pure iron, having a very small carbon content (carbon content does not exceed 0.15 percent), but usually contains some slag. It is tough, malleable, ductile and can be easily welded. However, it is too soft to make blades and swords, or at least for their cutting edges, which need to be made of steel with a higher carbon content.

Common reference to 'wrought iron' means iron of this composition. However, it should be confined to iron that has been wrought into a finished product.

wrought - purified by repeatedly beating with hammer.

Wrought iron has been used for thousands of years, and typically represents the "iron" that is referred to throughout history.

Eiffel Tower 1887-1889

ParisGustaf Eiffel

Wrought iron

Wrought iron

Galleria Umberto is a public gallery in Naples, southern Italy. It is located directly across from the San Carlo opera house. It was inaugurated in 1890 and was the cornerstone in the decades-long rebuilding of Naples--called the risanamento (lit. "making healthy again)--that lasted until WW1. It was named for Umberto I, king of Italy at the time. It was meant to combine businesses, shops, cafes and social life -- what today might be called a "mall". The design was by Emanuele Rocco and employed modern architectural elements reminiscent of a similar and earlier building in Milan.The "Galleria" is a high and spacious cross-shaped affair surmounted by a glass dome braced by 16 metal ribs. Of the four glass-vaulted wings, one fronts on via Toledo (via Roma), still the main downtown thoroughfare, and another opens onto the San Carlo Theater. It has returned to being an active center of Neapolitan civic life after some years of decay.Retrieved from "http://en.wikipedia.org/wiki/Galleria_Umberto"

The Home Insurance Company BuildingWilliam LeBaron Jenney, 1893Chicago

Steel

One of the early true skyscrapers. Steel framing was fireproofed with masonry

The Primary Metals of Construction

Aluminum weather resistance

Copper electrical, plumbing, roofing

Steel structural

AluminumKey Factors

Light weight lighter weight building enclosure system means a lighter structural frame which cost less

Key Factor

Weather resistance aluminum oxide forms a natural barrier to the affects of weather

Aluminum

AluminumForming process most aluminum components are formed by extrusion which yields very precise section

Finishes mill finishbright metal anodized color

CopperRoofing very long life

very expensive

Plumbing and electrical

SteelStructural framing

Roofing / Cladding

Interior products

Steel Forming methodsHot rolling method used to shape heavy steel beams

and columns by heating steel and passing back and forth through a set of rollers

Cold forming method used to form thin steel

components such as door frames and studs

SteelHot rolling:

Eliminates flaws and is used to make structural shapes such as wide-flange beams and channels.

SteelCold formed

Increases strength, but decreases ductility

SteelStrength 50,000 psi

Steel is the strongest of the three main structural system materials:

steel

concrete

wood

Steel is equally strong in both tension and compression.

High strength results in visually light weight structure

SteelRust requires protective coating

paint galvanizing

Fire protection spray on cementuous

coating insulates steel from heat which causes steel to weaken

-Spray-Cladding-Encasement (composite steel & concrete)

SteelRecyclable steel is

one of the most recyclable building materials. Recycled steel requires much less energy to produce a ton of steel than starting from raw ingredients.

Insensitive -The value of recyclable materials offsets the cost of demolition.

*Fun Fact: The automobile is the most recycled product in the U.S.

Steel A Kit of Shapes.

Examples of Standard Shapes of Structural Steel

http://bushwickmetals.thomaswebs.net/products.html

A Kit Of Shapes

SteelFabricationOff-site fabrication

On-site assembly

First prefabricated steel (wrought iron) structure

SteelFabrication coordinated by shop drawings

SteelConnections

Welding

Bolting

Rivets

Testing

X-ray

Self tensioning bolts

SteelOrganizing the Structural System

Grid Systems orthogonal radial

Organizing the Structural System

SteelGrid Hierarchy

Advantages of a grid

The grid establishes repetitiveness Repetitiveness simplifies fabrication and assembly processes

Open Web Joists

• Sometimes called bar joists are shop fabricated, standardized lightweight trusses made from hot-rolled or cold-formed steel sections.

• Used in a similar fashion to wood joist construction, and they are available in a variety of spans, depths, and load-carrying capacities.

• The open web has the advantage of permitting pipes, ducts, and conduits to pass through the joists within the floor construction depth.

Open-Web Steel Joists

Produced in 3 series

K-series span up to 60’ – depth ranges from 8” to 30”

LH-series (longspan) span up to 96’ – depth ranges from 18” to 48”

DLH-series (deep longspan) span up to 144’ – depth ranges from 52” to 72”

Spacing between OWJ-s ranges from 2’ to 10’.

• Metal decking is manufactured from sheet steel in a corrugated, ribbed, or cellular form. The edges overlap or interlock to form a working platform during construction and permanent formwork for a concrete floor slab.

• Most floor decking is now composite metal decking , which has deformed or patterned ribs that bond to the concrete so the deck and concrete act together as a unit to support the loads.

Preliminary Design of a Steel Structure Dimensioning

Corrugated steel roof decking depth of = 1/40 of the span (standard depth = 1”, 1 ½”, 2” and 4”)

Open-web steel joists depth of = 1/20 of span for heavily loaded floors or widely spaced joists. Depth = 1/24 span for lightly loaded floors, closely spaced joists and roofs. Typical joist spacing range 2’ - 10’

Steel beam depth = 1/20 of span (width usually 1/3 to 1/2 of depth)

Steel girder depth = 1/15 of span (width usually 1/3 to 1/2 of depth)

Triangular steel roof trusses depth = 1/4 to 1/5 of span.

Rectangular trusses depth = 1/8 to 1/12 of span.

Steel column size. Add up the total roof and floor area supported by the column. A W8 supports up to 3000 sq ft. W14 25000 sq ft.

Light Gauge Steel Framing

• Lightweight, or light gauge, metal framing is analogous to wood framing. Instead of wood studs, joists, and rafters, light-gauge steel members, made of cold-formed sheet steel, are used.

• Instead of using nails, connections are made with screws, bolts, or welds.

Light Gauge Steel Framing

• Light weight metal framing involved

relatively short spans, up to 32 feet,

and relatively light loads. • System has many advantages it is:

lightweight, incombustable,

and impervious to decay,

warpage, shrinkage

and termites.• More expensive than

wood framing

END

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