1. Properties of Steel

2. What is steel?
An alloy of iron (Fe26) and other elements, primarily carbon (C6)
-atomic number – number of electrons
-raw iron ore pellets from our earth’s crust (6% of our earth’s crust is made of iron) then a steel mill
Comes from our Earth’s crust – 6% is iron

3. How is steel made? Relatively easy and cheap to fabricate
After iron ore is mined, its melted at 2,800 degrees F
Carbon and other elements are then added

4. Steel It’s the most recycled material on the plant
Cheaper to recycle than to mine and manipulate iron ore
-environmentally friendly option
-sculpture was made of 2,000 pounds of scrap steel

5. Steel in the U.S. & THE WORLD
the U.S. was the largest producer and the lowest cost producer
The predominate material for construction of bridges and buildings
ASTM issues standards on materials and design
-now its China and India

6. Steel in buildings Steel frame – “skeleton frame”
Vertical steel columns and horizontal I-beams in a
rectangular grid to support floors, roofs, and walls
Made skyscrapers possible – 1st one was in Chicago
-steel framework and black aluminum facing

7. Why steel? advantages
Ease of fabrication, lower production cost, its recyclable
It also possesses desirable physical properties -

8. high compressive strength and very low tensile strength
Why steel? advantages
High Strength (particularly tensile strength)
Tension –pulling force
Compression – pushing force -
Concrete has
high compressive strength and very low tensile strength

9. Why steel? advantages High strength (particularly tensile strength)
High density too
A 2x4 steel I-beam can be designed to be stronger and lighter than a 2x4 of wood -

10. Why steel? advantages Uniform
Properties don’t change unlike in concrete or wood -

11. Why steel? advantages Elasticity
Can be temporarily deformed by a force and return its original shape & size
Follows Hooke’s Law accurately
One of the foundations of seismology – assess stresses and reactions -

12. Why steel? advantages Ductility – steel is a ductile metal
Can withstand extensive deformation under tensile stress before fracture
Gives you warning before failure takes place
-elements and constituents will vary steel’s ductility

13. Steel disadvantages Maintenance & corrosion
Susceptible to corrosion if exposed to air, water, acids, humidity, etc.
Environment of location needs to be assessed
Iron is oxidized (by O2 and H2O) and produces rust
Can add elements like copper or chromium
Or coat the steel (or galvanize) -

14. Steel disadvantages Fireproofing costs Steel is incombustible
But it softens and it’s strength decreases at high temperatures
Can cause building to partially collapse in the case of the columns
Concrete meets stringent fire codes
Asbestos was used back in the ‘70s
-asbestos was a popular material for fireproofing steel structures up until the early 1970s before the health risks of asbestos fibres were fully understood

15. Steel disadvantages Buckling
As the length and slenderness of a compressive column is increased, its danger of buckling increases -

16. Steel sections Easy to roll steel into any shape
The I, T, and C shapes are most common -

17. Steel sections - aesthetics
Rolled pipe or tubular cross-section
Popular in the U.S. for architectural aesthetics in exposed structures -

18. connections The glue that hold a steel structure together
Historically, major structural failures often involve failed connections
Connections fail when there’s unexpected force -

19. connections Welding – fusion by melting base metal and adding
filler metal that forms a joint (stronger than the base)
Greater level of skill, expensive, & requires inspections -

20. connections Bolts – screw threads and fasteners
Easy to do on-site, cheap, can be tightened
High-strength bolts are available -

21. connections
Rivets – are smooth and pounded into a drilled hole with a gun
Quick , simple, won’t shake loose -

22. Decking - Floors Corrugated sheets below a layer of concrete
and steel reinforcing bars
Bars help strength and limit cracking -

23. Questions? -