Steel in Construction - Essay Example

STEEL IN CONSTRUCTION Introduction In the advent of iron industry, buildings, infrastructures, dams and railway terminals were made of irons. Engineers and architect design their project in such a way that the designed iron works can resist the total load. Iron is a kind of ferromagnetic metal that is ductile, hard, and has high tolerance in, compressive, shear stress and torsion. These properties of iron are suitable for building constructions. Iron is reactive to other substance like when it reacts to oxygen and producing rust as the end product. There are different of iron depending on the combined materials. These combine material together with the iron will produce an alloy. Alloy was introduced so that some of the necessary properties of the other material will merge on the properties of iron. Some of the type of iron alloy is cast iron. Cast iron is made up of iron manganese, carbon and silicon and other impurities. Cast iron is hard, brittle, and nonmalleable. Unlike wrought iron, cast iron cannot be shaped but must undergo casting. Cast iron possesses the properties of brittleness and less tolerance to tensile stress. The compressive strength of cast iron made it a good material for building construction. Cast iron was first utilized as ornamental in a building like the fence and windows. The basic applications of cast iron in the industry were in automobile construction industry, agriculture machinery, kitchen ware, and iron piping and fittings. Wrought iron is another type of iron that has high significance in building industry. Wrought iron is composed of iron and little percent of carbon. Wrought iron is hard, ductile, malleable thus can be easily shaped. This type of iron has high tolerance in compressive, shear stress and torsion. Wrought iron usage is in decorative purposes because of its properties that can be easily formed in the desired shape. In the 19th century, modern steel was introduced to the world as a component in building’s infrastructures. Steelmaking was first used in China and Japan in 600-800 AD. Steel is composed of iron and carbon. Steel has the properties of tough, rigid and can be easily fabricated. The basic uses of steel are plates, sheets and structural shapes like I-beam and channels.(CONSTRUCTION, 2002) Comparison of selected building The two buildings that will be structurally examine are the Crystal Palace that is cast and wrought iron made and the DeVos Place convention center which is made up of modern steel frames. With the birth of Iron Age, many buildings were erected with the use of cast and wrought iron. One of these was the Crystal Palace build in mid 18th century by Sir Joseph Paxton. The building was considered architecturally significant and mathematically simple. It was the chosen building because it pioneered the utilization of cast and wrought iron as a basic component in a structure of building. It was considered a great iron building.(Dyke, 2004) The other building that was chosen to analyze the structure was the DeVos Place convention center located at Grand Rapids, MI. DeVos Place exhibits the use of modern steel as structural frames. Not only was the aesthetic value considered in the selection of the two buildings, but mainly on the structures and the element of these structures that was designed. Cast, wrought iron and modern steel have the same and some distinct properties that are always considered when using these in construction of buildings. These metallic materials are combined with different impurities to produce the desired effect. Example of this is carbon. Carbon is mixed with these materials to strengthen the stiffness and toughness of iron and steel. The end product is called alloy and has many nomenclature depending on the amount of carbon added. The three materials are considered tough which means that it has high resistance to wear. These materials are also high tolerance on different stresses. Cast iron is designed to resist compressive stress and it’s weak on tensile, shearing stress and torsion. With this, wrought iron was introduce to oppose tensile, shearing and torsion. This is for the reason that trusses and frame members are always experiencing tensile, compressive, shearing and torsion at the same time. But wrought iron fabrication is a difficult process. It needs an expertise to produce wrought iron. Modern steel, which was commenced in the mid 19th century because of the breakdown of some building structures made of cast and wrought iron. Ashtabula Bridge was destroyed because of some natural disaster that led to the failure of the said structure. Modern steel then was introduced in engineering applications. Modern steel is a special; kind of steel that is thermo mechanically treated. It is one of the greatest findings in the field of engineering specialized in structural engineering. Modern steel manufacturing is develop so that a state of the art product will produce thus the original properties of a steel will be improved to meet the requirements in building a infrastructure. It has high weld ability thus making it easy to produce. Characteristics of the selected building Crystal Palace Crystal Palace was the first building to use iron as structural frames. Crystal Palace was designed to have a cantilevered iron frame. Almost all the frame of the palace is made up of combination of cast and wrought iron. Columns and beams were also constructed to support the building using an iron. Columns were made of cast iron which experiencing compressive stress. And beams were made of combination of cast and wrought iron because beams experience both compressive and tensile stress. Above the building is a suspended roof which is also made of iron. The roof has circular repetitions of iron bars. The architect of Crystal Palace introduces also the concept of truss. The trusses were triangular in shape because this is the most strategic formed of the truss members to resist loading. The triangular formation of the truss lessens the moment arm. The lower part is made up of cast iron. (Peters, 1987) The building was also made up of glass. Tons of glass was used in the construction of the building and these were supported by cast iron columns. The iron materials used in the construction were 372 roof trusses, 3000 cast iron columns. Each column has a height that varies between 16 to 18 feet. The columns used have bigger area on the lower part that will eventually lessen the compressive stress. The outer diameter of the columns is 8 inches. The columns are made of cast iron to counter act the compressive stress brought about by the load. At the bottom of each column is a concrete box that has the dimension of 2’-3’. This concrete will act as the base of the column and addition of the stability of the erected column.(Peters, 1987) There were nine different kinds of girders and trusses used in the construction of Crystal Palace, each having a length of three feet. In this structure, different kinds of members with different stress capacity were used. DeVos Place convention center The expansion of DeVos Place convention center was fueled with the use of the modern steel technology. Modern steel was used in the construction of the super-structure mainly because of the possessed properties of modern steels. The main design of the building was the used of two long box trusses that support the roofing structure of the building and the force created by the moving air. (Fig 4) The beams used in the box trusses were from group 4 and 5 W-shape steel and these beams were pre tested to meet the standards in structure construction. The grand gallery and exhibit hall were also constructed using modern steel. The construction of the grand gallery was been difficult for the structural engineers and architects but with the use of computer-aid design programs, they find a way to minimize the problem. The challenge for the structural engineers and architects is to build the grand gallery which is free from columns. To support the roof structure, they fabricate 17 steel-bent beam columns. Each of this was fabricated so that the lower part of the beams are narrower compared to the upper part. (Fig 5) The construction of the exhibit hall was also a challenge. Because of the desire that the space is free from columns and the application of concrete will lead to higher cost, the engineers designed the exhibit hall to be free from columns using long span box trusses. Each box trusses were supported by a huge box concrete. The box trusses members were made of combination 50 ksi and 65 ksi steel members. The box trusses were constructed so that the members are diagonally lined and some are squared. This is because that the box trusses experience many loading like the vertical, horizontal ant the wind pressure. (Fig 6). (Gustafson, 2004) Buildability of iron/wrought iron and modern steel From the three kinds of materials, cast iron is considered to have an ease in producing it. Iron is melted with some substance like carbon, manganese and silicon. It is then melted again. The use of cast iron in building industry is advantage because of the high resistance to compressive stress. Cast iron making is crucial because an excess or less amount of impurities addition will lead to some undesirable characteristic of the product. Brittleness will be expected if excess amount of carbon is added. While wrought iron making is laborious work because the melted iron and carbon is molded and rolled to the desired shape. Expertise in iron making is needed in the production of wrought iron. Wrought iron is used mainly in beams that experience tensile stress. In the advent of Iron Age, these two materials were the prominent materials in construction of buildings. The cost for the production and usage of these materials are less expensive compared to the traditional method that utilizes wood and stones. The introduction of modern steel to the industry was a great discovery because super structures were built after the world war. Modern steel compared to cast and wrought iron has higher toughness and resistance to many types of tresses. Steel making is done with special technique like the steel wire is passed from cold water. After this, the steel wires are removed from the cold water thus the heat transfer occurs from the surface to the core and this will produce a hole on the center. This will make the steel ductile and ease in welding operations. (CONSTRUCTION, 2002) Both of the discussed buildings met the standards. The Crystal Palace met the standards of British Standards and Euro codes in building the structures. DeVos Place convention center also followed a set of standards. They used these standards as guide in what materials to be used. They followed the standards in United States-1996 BOCA code. Appendices Figure 1. Front view of Crystal Palace Figure 2. Combination of cast/wrought iron braces in Crystal Palace Figure 3. Upper portion of Crystal Palace Figure 4. Two large box trusses Figure 5. Steel-bent beam columns Figure 6. Longitudinal view of the box trusses References: Read More