Zimmerman Carley Professor Ziff November 12, 2007 Materials Extra Credit TEST 1 Problem 12 When using wood during construction, design, and detailing processes, it is important to understand the two types of wood that provide the options in the project. Hardwoods and softwoods have many different uses, but when used wrongly, can ruin a project. Hardwood is of higher density and hardness than softwood and have broad leaves and enclosed nuts or seeds. Hardwood species are more varied than softwood. There are about a hundred times as many hardwood species as softwoods. Hardwoods are far more resistant to decay than softwoods when used for exterior work, but are much more expensive when used that way. Softwood is wood from conifers, or needle-bearing trees and generally is softer than hardwoods in the building process. There is an exception though; Douglas fir is harder and stronger than many hardwoods. Also balsa, technically a hardwood, is much softer than even most softwoods. The difference between softwood and hardwood is found in the microscopic structure of the wood. Softwood contains only two types of cells, longitudinal wood fibers and transverse ray cells. Softwood has a huge range of uses and it is a prime material for structural building components. It is also found in furniture and other products such as moldings, doors, and windows. Softwood is also harvested for use in the production of paper, and for various types of board.
Problem 24 Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral (PVB), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a "spider web" cracking pattern when the impact is not enough to completely puncture the glass. Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered. Some examples of uses of laminated glass are shop fronts, windshields, skylights, patio doors, and many more. The PVB interlayer also gives the glass a much higher sound insulation rating because of the damping effect and also because it blocks most of the transmitted UV light. Laminated glass was invented in 1903 by the French chemist Edouard Benedictus, inspired by a laboratory accident. A test was done with a glass flask that had become coated with the plastic cellulose nitrate and when dropped shattered but did not break into pieces. Benedictus fabricated a glass-plastic composite to reduce injuries in car accidents. The first widespread use of laminated glass was in the eyepieces of gas masks during World War I before automobiles starting using it. Problem 25 Gypsum board is a very important factor in the structure and protection of most buildings currently. It is a common manufactured building material used globally for the finish construction of interior walls and ceilings. A gyp-board panel is made of a paper
liner wrapped around an inner core made primarily from gypsum plaster, the semihydrous form of calcium sulphate. Drywall is typically available in 4 ft wide sheets of various lengths. Larger sheets make for faster installation, since they reduce the number of joints that must be finished. The most commonly used drywall is one-half-inch thick. For soundproofing or fire resistance, two layers of drywall are sometimes laid at right angles to each other. Gyp-board provides a thermal resistance R-value of 0.32 for threeeighths-inch board, 0.45 for half inch, 0.56 for five-eighths inch and 0.83 for one-inch board. In addition to increased R-value, thicker drywall has a higher sound transmission class. North America is one of the largest gypsum board users in the world with a total wallboard plant capacity of 40 billion square feet per year. The gypsum board market is one of the biggest beneficiaries of the housing boom and an average new American home contains more than 7.31 metric tons of gypsum. Problem 41 Float glass is a sheet of made glass by floating the molten glass on a bed of molten tin. This method gives the glass uniform thickness and very flat surfaces. One common example of float glass is modern window glass. In 1959 the Pilkington Brothers Company developed the first successful commercial application for forming a continuous ribbon of glass using a molten tin bath on which the molten glass flows across the bed unhindered to the limit of its free flow because of the influence of gravity and surface tension. The success of this process was because of the careful balance of the volume of glass fed onto the bath, where it was not flattened by rollers, but by its own weight. Before the development of float glass, larger sheets of plate glass were made by casting a large puddle of glass on an iron surface, and then grinding and polishing both sides to
smooth clarity, a very expensive process. From the early 1920s, a continuous ribbon of plate glass was passed through a lengthy and expensive series of inline grinders and polishers, helping to reduce glass losses and production costs. Glass of lower quality, sheet glass, was made by drawing upwards from a pool of molten glass a thin sheet, held at the edges by rollers. As it cooled the rising sheet stiffened and could then be cut. The two surfaces were less parallel and of lower quality than those of float glass. TEST 2 Problem 30 Marble is a metamorphic rock resulting from regional metamorphism of sedimentary carbonate rocks, either limestone or dolostone, or metamorphism of older marble. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock. Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, or iron oxides, which were originally present as grains or layers in the limestone. White marbles, like Carrara in Italy, Royal White and Beijing White in China, have been prized for sculpture since classical times. This preference has to do with the softness, homogeneity, and a relative resistance to shattering. Also, the low index of refraction of calcite allows light to enter several millimeters into the stone before being scattered out, resulting in the waxy look which gives life to marble sculptures of the human body. Colorless or light-colored marbles are a very pure source of calcium ...