Use of Wood as a Building Material

Use of timber as a Building MaterialWood is quite unique when comp bed to to the luxuriouslyest degree building solids apply today devoted that its actual makeup is a consequent of congenitally grown biologic tissue (ill.18). Thus, the material makeup and body social structure of timberwind instrument is signifi cig arttetly variant than that of most industrially produced, identical materials. Upon close examination, timber posterior be described as an anisotropic natural fictional character complicated. In line of work to isotropy, which constitutes identical properties in all directions of a material, anisotropy concerns the property of being directionally dependent. For instance, mavin outhouse see this in the way that forest can wriggle easily in the tangential axis vertebra (ill.19) which is the direction perpendicular to its metric iota direction. When examining timberwind instrumentwind instrumentwind from any given weight, unitary can identify mat erial characteristics and behaviours specific to that angle, relative to the materials chief(prenominal) grain orientation. That is to say, should matchless examine the material properties of forestwind instrument at an angle 45 degrees to the main grain orientation, one will discover properties extremely different than those obtained from an angle 90 degrees to the main grain orientation.The directionally dependent property of wood is a result of the horizontal or vertical orientation of the individual prison electric stalls and the arrangements of produce layers in a channelise.1 Throughout architectural history, this inherent heterogeneity of wood as well as its complex material characteristics check oft been characterized as deficiencies by architects, engineers and members of the timber industry.2 This can be traced to the fact that most send offs and body structure methodologies used today require the use of materials bearing minimum variations in their properties and behaviours in bon ton to satisfy the need for isotropic structures.In contrast, this thesis views woods complex material makeup and its capacities as significant advantages rather than deficiencies. Further more(prenominal), it aims to understand these interesting characteristics of wood and employ them through with(predicate) an informed design butt against.In addition to these complex material properties, wood overly presents many favorable characteristics including diversity, weight, strength, appearance, workability, cost and availability. Another factor that makes wood a very appealing material today concerns its overall bionomic advantages. In light of the environmental challenges that the built environment is facing today, it is go increasingly recognized that very few building materials can match forest environmental benefits. Wood is a natural, re sassyable material that h greys a very low level of embodied energy. It is known for its ability to deoxidize carbon dioxide emissions by storing CO2 and in addition by substituting for materials with a high carbon content3. In this manner, the use of wood actually produces a positive carbon footprint.4 Wood is also an extremely energy good building material in its production. For example, wood requires 50 times little energy in its manufacturing than steel to find out a given geomorphological asperity as a whole.5Unlike many natural resources, plants rest of a renewable resource. With c arful forest management, one can ensure that forests thrive and continue to provide the many benefits to which we start become accustomed. Foresters can calculate an allowable cut of trees per grade for any given forest argona that will secure a stable harvest. Tree soil is yet another way of sustainably satisfying todays demand for wood. Programs at oak Ridge National Laboratory have engineered a breed of ace trees that can grow at rapid speeds in order to manufacture a substantial amount of bio ma ss in a star given acre. These engineered trees are being farmed at tree farms such as the Boardman Tree Farm LLC, and are redefining modern forestry (ill.20). The Boardman Tree Farm plantations are laid in eastern Oregon, United States, where dry desert fine-tune has been transformed into a thirty thousand acre farm. This plantation currently has lxx million trees and is capable of producing half a million trees every yr to satisfy demands. The plantation harvests five acres of trees every day in order to maintain this continuous cycle.6As a result of woods naturally-grown origin, its unique material composition accounts for most of its properties and characteristics.7 The aim of the thesis is to search some of the potential ways of utilizing the material properties and specific material characteristics of wood in the design field. In order to do so, the heterogeneous structure of wood must first be understood in great detail.Wood can be defined as a low-density, cellular, c omposite material and as such, does not readily fall into a adept class of material, but rather overlaps a number of classes. In hurt of its high strength performance and affordability, timber remains the worlds most productive fibre composite. On the microscopic scale, one can describe wood as a natural fiber composite.8 (Ill.21)Wood cells are comprised of layers, upon which cellulose microfibrils pass away like fibers embedded in a matrix of lignin and hemicelluloses, reinforcing the assembly as a whole. Due to this makeup at the microscopic level, wood assigns a number of properties with materials like synthetic composites, beef up plastics, fiberglass, and carbon fiber. Similar to wood, these materials are characterized with relatively low stiffness in combination with relatively high structural capacity. In other words, wood contains innate elastic properties specially well-suited for construction methods that seek to employ elasticity in achieving complex light struct ures from initially planar elements.What follows is intended as a brief overview of the material composition of wood. Under rest the anatomical aspects of wood is imperative to the research and investigations that have been conducted.In contrast to building materials that are specifically designed and manufacture to suit the needs of an architect or an engineer, wood is a result of the biological tissue functions that take place in a tree. Although at that place exists a wide variety of species of trees in the world, all trees, despite their diversity, share certain characteristics. Trees are all vascular and perennial which means they are capable of adding yearly growth to previously grown wood. The growth move of a tree occurs in the cambium, a thin layer of supporting cells between the bark of the tree and the inner stem structure. (Ill.22) Cambial cells have thin walls and divide themselves lengthwise to grow into devil new cells. next the cell division, one of the 2 cells en big(p)s to become another cambial bring forth cell while the other either matures into a bark cell or forms towards the inside of the cambium to become a new wood cell.When the capital wood cells reach maturity and develop into their mature size, a indirect wall is constructed from long chain hemicellulose and cellulose molecules. The long chains of cellulose molecules are lie in a direction parallel to the long axis of the cells and reinforced by lignin (ill.23). Lignin is an integral sectionalization of the woods cellulous structure because it provides support for the cells. It is also the material that gives rigidity to plants.9 The diffusion and orientation of the cells along with the material structure of the cell walls determine most of the resulting characteristics and properties of wood.10Trees are characterized into two types wads and hardwoods (ill.24). The terms softwood and hardwood do not signify softness or hardness of wood. The two terminologies are related to the botany of the species and to the way in which a tree grows. The differences between the two types of wood can be seen in the cellular structure of the materials. In the relatively simple cellular structure of softwood, nine-spot tenths of the wood volume consists of one cell type called tracheid, while the conflict consist of ray tissues. Tracheids are fiber-like cells and have a length-to-width ratio of vitamin C1, meaning that they are approximately one hundred times lifelong than they are wide. The tracheid cells are ordered parallel to the stem axis located in the radial layers of the tree and are responsible for the transport of water and minerals throughout the tree.In contrast, a much greater variety of cell types and arrangement configurations are present in hardwoods. In addition to tracheids, hardwoods also contain vessels, rays and fiber cells. Vessel elements in hardwood have a large diameter and thin walls, containing no end-to-end walls. As a result, they are arranged in an end-to-end formation that is parallel to the stem axis of the tree, forming continuous channels that carry sap through the tree. Unlike vessels, fiber cells are much smaller in diameter and have slower cell walls and possess closed tapered ends (ill.25). In both softwood and hardwood, the structure, distribution and orientation of cells are the determining factors of the anisotropic, structural, and hygroscopic characteristics of wood.11The anisotropic and hygroscopic characteristics of wood resulting from its internal cellular structure have traditionally been regarded as tough in the practices of architecture and structural engineer, especially when compared to more homogeneous, stable, industrially produced isotropic materials like steel, plastic or glass. In design approaches within architecture, engineering and timber industries, knowledge of woods material composition and characteristics has in general been employed to counterbalance its complex material behaviours.12 For instance, the development of engineered industrial wood products (ex MDF, or cross-laminated-timber) came as a response to the heterogeneous composition of wood. These wood products are capable of producing a material that is much more solid and which provides isotropic material characteristics.Unfortunately, the design opportunities that could be made possible using the innate heterogeneous characteristics of wood are too often unmarked in todays construction projects. In fact, particularly in North America, the construction material of wood is often no longer referred to as such. Instead, wood is referred to as a dimensional building element, such as a 24. The aim of this research is to propose an alternative approach to design which views woods complex material composition and related behaviours as advantageous rather than problematic. Such an integrated design approach can perhaps contribute towards a renewed appreciation for the behavioral capacities of wo od and the rich design opportunities that can be realized thanks to the natural anatomy of this material.three-ply plyboard and veneer are unmistakably industrially-produced materials. However, remote other industrially-produced materials such as steel, glass, plastic, MDF or particle board, three-ply plyboard and veneer are anisotropic materials. This signifies that the properties and behaviours of these materials vary significantly in singing to the fiber direction. For example, veneer and plyboard encounter considerable differences in stiffness depending on the grain direction. The compressive strength of wood differs significantly depending on grain direction, as do most of its other mechanical and material properties. The side by side(p) section details the manufacturing process of veneer and plywood in order to better understand the material exploration that will be presented in Chapter 3.Plywood may appear to be a relatively new industrially-produced wood product, howev er its concept is in fact very old and can be traced back to more than 5,000 years. Before the word plywood was invented in the 1920s, the process was referred to as veneering. One of the earliest traces of plywood was imbed in the tomb of King Tutankhamun, an Egyptian Pharaoh who ruled around the year 1334 BC. The discovered pieces of plywood were remains of coffins made of six layers of wood, each 4mm thick and held in concert by glue and wooden pegs.13 The plywood remains were fabricate using the same fundamental techniques as today. Like modern plywood, the grains of the layers where arranged perpendicularly with each layer for strength14 (ill.26). From this period onwards, veneering techniques became increasingly far-flung throughout the world. Thanks to the development of tools and technology over the years, veneer thicknesses were reduce and new adhesives (ex glue made from bone, sinew and cartilage) were used to bond the layers together with heat.15Although plywood is mad e much in the same way today, modernised adhesion techniques and tools used in its production have improved significantly, make it one of the most affordable and easily-produced building materials. Both hardwoods and softwoods are used in the production of plywood. The typical sequence of operation involved in the production of plywood is as followsThere exists a long standing discourse on the subject of sheet materials in architecture, in part because these are so ubiquitous in conventional construction. Expanding the understanding of these materials is blue-chip to the architectural profession, as it allows one to discover new potentials concerning materials which are already familiar. Being a sheet material, plywood thus affirms many advantages as a subject of research and experimentation. Like other sheet materials, it can facilitate the creation of complex geometry using initially planar elements. Three-ply plywood is the material of choice for this thesis due to its abilit y to offer high amounts of flexibility in one direction, without compromising its strength. Three-ply plywood, as previously described, is made up of odd layers, two of which are oriented in one direction, while the center(a) layer lies perpendicularly to the outer(prenominal) layers. Thus, due to the predominant fiber direction present in the two outer layers, three-ply plywood possesses a natural tendency to deviate perpendicularly to this grain direction. The core of the assembly, otherwise known as the center layer, provides strength to the assembly by offering resistance to the predominant fiber direction. As a result, the plywood assembly is less likely to watch or snap when being bent because it is reinforced by one interior sheet containing fibers running perpendicular to the outer layers.Knowledge of the manufacturing process for plywood is important for this research because it provides an introduction to lamination techniques that can be set ahead utilized in the mat erial investigations and implementations that will follow. The process described preceding(prenominal) elaborates on the procedure involved in the mass-produced manufacturing of flat plywood sheets used in the building industry. However, the process of lamination need not purely apply to planar surfaces, but also to the development of three-dimensional forms.1 J. M. Dinwoodie, tone Its Nature and Behaviour (London EFN Spon, 2000).2 T. Herzog, Holzbau Atlas (Basel Birkhuser, 2003).3 A. Alcorn, Embodied Energy Coefficients of Building Materials (Wellington centralise for Building Performance Research, 1996), 92.4 Joseph Kolb, Systems in Timber Engineering Loadbearing social organisations and Component Layers (Basel Birkhuser, 2008), 19.5 J.E Gordon, Structure (Cambridge Da Capo Press, 2003).6 A Resource That Lasts Forever, last modified July 23, 2014, http//www.greenwoodresources.com/7 Barnett and Jeronimidis, Wood feel and its Biological Basis (Oxford Blackwell CRC Press, 2003) .8 heterogeneous Materials Natural Woods. Last modified July 23, 2014, http//www.technologystudent.com/joints/composit1.html.Composite materials, sometimes referred to as composites, are materials composed of two or more component parts. These component parts may have different sensual or chemical properties and when carefully inspected, they appear as separate parts, bonded together, forming a composite material.9 R. Bruce Hoadley, Understanding Wood A Craftsmans Guide to Wood engine room (Newtown, Conn. Taunton Press, 2000).10 R. Wagenfhr, Anatomie des Holzes Strukturanalytik, Identifizierung, Nomenklatur, Mikrotechnologie (Leinfelden-Echterdingen DRW-Verlag, 1999).11 R. Wagenfhr, Anatomie des Holzes Strukturanalytik, Identifizierung, Nomenklatur, Mikrotechnologie (Leinfelden-Echterdingen DRW-Verlag, 1999).12 T. Herzog, Holzbau Atlas. (Basel Birkhuser, 2003).13 Lucas A. and Harris, Ancient Egyptian Materials and Industries (Dover Publications 4th edition, 2011), 451.14 H. Ta ylor John, Death and the afterlife in Ancient Egypt (Chicago U of Chicago, 2001), 218.15 L. Patrick Robert and Minford J. Dean, Treatise on Adhesion and Adhesives (CRC Press, 1991), 3.