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18 - CIVE 2700 Civil Engineering Materials Winter 2007 Wood...

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CIVE 2700 – Civil Engineering Materials, Winter 2007 1 Wood Professor George Hadjisophocleous, Ph.D., P.Eng. Carleton University Department of Civil and Environmental Engineering Ottawa, Ontario CIVE 2700 – Civil Engineering materials, Winter 2007, 17.2 Introduction Wood is one of the oldest material of construction • Applications: – Shipbuilding – Bridges – Railroad ties – Floors – Walls – Cabinets
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CIVE 2700 – Civil Engineering Materials, Winter 2007 2 CIVE 2700 – Civil Engineering materials, Winter 2007, 17.3 Introduction Wood is popular because of: – Simplicity in fabrication – Lightness – Reusability – Insulation from heat, sound and electricity – Esthetically pleasing appearance – Resistance to oxidation, acid attack, and salt water – Environmental compatibility Annual production of wood 10 9 tons, equal to world production of iron and steel and comparable to concrete 4x10 9 tons CIVE 2700 – Civil Engineering materials, Winter 2007, 17.4 There are two basic classes of trees - the broadleaved or deciduous trees, that produce hardwoods, and the coniferous or evergreen trees, that produce softwoods. The terms “hardwoods” and “softwoods” are not always descriptive because some softwoods are harder than some hardwoods. Types of Wood
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CIVE 2700 – Civil Engineering Materials, Winter 2007 3 CIVE 2700 – Civil Engineering materials, Winter 2007, 17.5 There are more than 100 species of broadleaved trees in Canada, but only a small percentage of these are used commercially. The leaves change colour and shed from the tree before winter Hardwoods CIVE 2700 – Civil Engineering materials, Winter 2007, 17.6 Softwoods There are fewer species of conifers - only about 30. These trees bear cones and most of them have needle-like leaves all year round. Douglas Fir is the largest conifer in Canada. Sometimes it grows over 90 metres high and four and one half metres in diameter. Softwoods comprise more than 80 percent of the total volume of standing timber in Canada, and account for most of Canada's commercial lumber and wood products.
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CIVE 2700 – Civil Engineering Materials, Winter 2007 4 CIVE 2700 – Civil Engineering materials, Winter 2007, 17.7 There are several easily visible layers in the tree. The first layer, the outer bark, provides protection for the tree. For some species, such as Poplar, it is very thin. For others, such as Douglas Fir, it can be very thick, sometimes more than 10 centimeters. Tree Layers CIVE 2700 – Civil Engineering materials, Winter 2007, 17.8 Moving into the tree, the next layer is the inner bark which stores the nutrients and transports them down through the tree. Just inside this layer is a very thin, invisible layer, the cambium. It produces new growth in girth of the tree. It produces inner bark on the outside and sapwood on the inside.
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