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Author: haroonkhan

  • Structure of Exogenous Trees

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    by

    haroonkhan
    in

    A cross-section of an exogenous tree is shown in Fig. 10.1. It shows almost distinct concentric rings called annual rings. Pith is the innermost central portion consisting of cellular tissues. The inner annular area surrounding the pith is called heartwood. Heartwood is the one which is used for all engineering works. The portion between the cambium layer and the heartwood…

  • Exogenous Trees

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    by

    haroonkhan
    in

    These trees grow outwards by the addition of rings of young wood. A cross-section of these trees shows distinct approximate concentric rings called annular rings. Timber from such trees is mainly used in engineering works. They are further classified into two types, viz., softwood and hardwood. (i) Softwood Softwoods have needle-like leaves and are also…

  • Endogenous Trees

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    haroonkhan
    in

    These trees grow by the formation of layers. In such trees new wood crosses and penetrates the fibres of the wood previously formed, e.g., bamboo, palmyrah, coconut, etc. Such trees are not useful for engineering works.

  • Classification of Trees

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    haroonkhan
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    According to the manner of growth, trees may be broadly classified as Endogenous trees and Exogenous trees.

  • TREES

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    haroonkhan
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    Basic Structure of a Tree A tree consists of a trunk, a crown and roots. The functions of the roots are to implant the tree in the soil, absorb moisture and mineral substances it contains and in turn supply them to the trunk. The trunk supports the crown and serves to provide water and nutrients…

  • INTRODUCTION

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    haroonkhan
    in

    Timber is a product of wood from felled trees suitable for construction purposes. Timber is one of the oldest and natural civil engineering construction materials. Three terms pertinent to timber one of interest. They are: Wood, as a building material, has a number of valuable properties, viz., relatively high strength, low bulk density, low heat…

  • Sunshade Unit

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    haroonkhan
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    Sunshades are made 75 mm at the cantilever end and tapered upwards to the depth of the lintel. They come monolithic with lintel. On an average the projection will be 60–90 cm. The main rods of the cantilever of the sunshade can be 8 mm rods at 10 cm centres with 8 mm distributors at…

  • Precast Shell Units

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    haroonkhan
    in

    Plain or slightly reinforced concrete can be used in the form of precast shell roofing. A suitable frame is made to cast the shell unit. A hessian cloth is spread over it. The cloth is given a sort of sag to maintain the shape of the shell. To regulate the thickness a thin frame of…

  • Roofing and Flooring Elements

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    haroonkhan
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    Prefabricated reinforced concrete battens are used instead of wooden battens. For sloping roof, precast reinforced and prestressed concrete trusses may be used. Plain precast concrete tiles can be used for roofing and flooring flat roofs.

  • Door and Window Frames

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    haroonkhan
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    Door and window frames can also be prefabricated. Steel bars of about 4–40 mm in diameter run through the frames of the doors or windows. Suitable hard wood blocks are used for fixing hinges, etc., to them. Concrete is vibrated on a table vibrator and then poured into the mould which ensures a durable mix.