The+evolution+in+the+use+of+metals+in+history

carola_lc13: Hi

Michelle Perticarari: hey girls!

carola_lc13: Girls what do you think about the advantages of iron and steel over stone and brick?

Rebeca Peña: hello my friends

Rebeca Peña: well, with iron and steel, there can be built stronger and taller structures than with stone, brick or wood. Also, with less expendidure of material, there can be produced greater unsupported spans over openings and interior or exterior spaces.

Michelle Perticarari: yeah I think so too, so why do you think those materials are important after the 20th century?

carola_lc13: Because the evolution of steel frame construction in the 20th century entirely changed the concept of the wall and the support. Steel and iron became an important part for construction, since they give a better support and resistance of the structures. Before the 20th century, metals played an auxiliary role, after that, they became the most important part of a building. Metals were used for bonding masonry (dowels and clamps), for tension members (chains strengthening domes, tie rods across arches to reinforce the vaults), and for roofing, doors, windows, and decoration.

Rebeca Peña: so, since steel became so important i would like to know what are its characteristics

Michelle Perticarari: I've done some researching and I found out that steel is uniformly strong, elastic, and workable. It has a high resistance in all stresses (tension, compression, and bending) wich can be closely calculated. That's why it's used for structural elements by itself or with concrete (as in reinforced concrete) carola_lc13: Now that we know the characteristics, maybe we can discuss about the disadvantages of steel and what solutions have been found?

Michelle Perticarari: I think the disadvantange of steel is that it needs a surface covering. Because it's affected by corrosion when left in outdoor spaces, however, stainlees steel has been created for those exposed surfaces. Also, other light metals, such as aluminum, are used for external purposes because of their weather resistance.

Michelle Perticarari: Have you guys heard the term welding? Why is it important?

Rebeca Peña: yes, i've found that welding is the join of metals by applying heat. It is important because it allows to produce joints with less labor and material. The result is a rigid, continuous structure in which the joint is as firm as the member and which distributes stresses between beams and columns.

Rebeca Peña: personally i have a special interest in buildings that are made out of steel, but do you guys know what shapes are formed with steel?

carola_lc13: I've heard that many shapes are formed with steel, such as: plates, angles, I beams, and U-shaped channels. And that is possible thanks to the elasticity of this material.

carola_lc13: Talking about steel and materials of construction, are aluminum and stainless steel heavy metal alloys?

Michelle Perticarari: No, I've read that aluminum and stainless steel are light metals.

carola_lc13: Well, i gotta go girls

carola_lc13: nice to talk to you

Michelle Perticarari: Yeah me too, bye girls!

Michelle Perticarari: see youu!

Rebeca Peña: ok, bye bye see you later alligator =)