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CIVIL ENGINEERING MATERIAL
CHAPTER 7.0 TIMBER
(IMP FOR 7 – 15 MARKS)
Prepared By:
Er. Pramesh Hada
MSC in Urban Planning
B...
TIMBER
Timber : Sources, Types, Classification,
Characteristics, Advantages & Uses.
Growth & Structure of Exogenous Plants...
TIMBER
•Is one of the important construction materials.
•Used as structural elements in buildings, widely for
doors, windo...
• When tree has been cut down and its stem and branches are
roughly converted into pieces of suitable length, then it is
k...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
PROPERTIES OF TIMBER/WOOD
Physical Properties :
1. Density
- light — very light: density less than 550 kg/m3, eg.
bamboo
-...
5. Swelling (Increase in size)
- It is increase in linear and volumetric dimension on
absorbing moisture.
6. Sound conduct...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
MECHANICAL AND THERMAL PROPERTIES OF
TIMBER/WOOD:
As wood is natural material there is different
mechanical properties for...
CHARACTERISTICS OF GOOD TIMBER (PU 2010)
Uniform color, strong, durable and workable
Straight and compacted fibers
Fresh c...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Fibers in timber
Er.PrameshHada,Asst.Professor,civil
Enginee...
ADVANTAGES OF TIMBER: (PU 2011)
availability: source and transportation
strength: light weight and higher strength
easy to...
USES OF TIMBER
It is mainly used for following categories of works
(i) It is used for construction purposes including buil...
HOUSEPOSTS
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDe...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
DISADVANTAGES OF TIMBER: (PU2011)
Defects in timber can reduce the life of wood.
Affected by relative humidity, fungi, ins...
Wood is a product obtained from the tree.
In simple classification of tree, it can be classified as:
1. Standing timber - ...
1. ENDOGENOUS TREE
Trees grow in inward direction with the addition of fibrous (like
of jute) layer at tip portion, i.e th...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
EXOGENOUS TREE
Deciduous tree
Are characterized by flat and broad
leaves which fall in autumn season and
new one appear in...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
DIFFERENCE BETWEEN HARD WOOD AND SOFT
WOOD (CHARACTERISTICS)
Aspects hard wood soft wood
Annual rings Indistinct Clearly d...
SISHAM TREES
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
Engineering...
SAL TREE
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepa...
TEAK WOOD
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDep...
PINE TREES
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDe...
DEODAR TREES
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
Engineering...
GROWTH OF A TREE
Roots of the tree suck a solution of salts from the soil in
spring season.
Salts are food for the tree an...
STRUCTURE OF A EXOGENEOUS TREE (PU 2009,2010)
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
• Pith/Medulla...
Pith/ medulla/core:
It is first formed portion of trees.
It consist entirely cellular tissues and nourishes the plant in y...
Sap wood:
Outer annual rings between heart wood and the cambium layer
Light in color and weight as well
Indicates recent g...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
MICROSTRUCTURE OF WOOD
Structure of wood apparent only at great magnifications is called
microstructure.
If study through ...
Conductive cells: serves to transmit nutrients from
roots to the branches and leaves
Mechanical Cells: these cells are elo...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Resinous wood
Er.PrameshHada,Asst.Professor,civil
Engineerin...
DEFECTS IN TIMBER (PU 08,09,10,12,13)
Defects are either due to growing phases of tree or defect
occurring after cutting t...
2. Star Shake
- It is confined in the outward portion
and diminishing towards center.
- It occurs due to frost action and ...
4. Cup or Ring Shake
- Is the separation of tissue along annual
rings
- If the shake is whole round the annual
ring then i...
6. Knots
- This defect occurs due to formation of annual rings at right
angles to surface and also due to twisting of fibe...
7. Twisted fibers
- This defect occurs due to wind velocity constantly turning trees in
one direction only.
DEFECTS IN TIM...
9. Druxiness and Foxiness
(Druxiness is a term that is defined as a disease that is
found in timber or wood. It is caused ...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
SEASONING OF TIMBER: (PU 09,10,11)
Wood is hygroscopic material, dry wood absorbs moisture from
surroundings
Freshly cut w...
FOLLOWING ARE THE DIFFERENT OBJECTIVES OF
SEASONING:
Timber to burn readily, if used as fuel
Decreased the weight of timbe...
METHODS OF SEASONING OF TIMBER:
Natural seasoning
Air seasoning/ drying
Water seasoning
Artificial seasoning
Air seasoning...
AIR SEASONING:
This method is economical one
Takes 2 to 4 years
Covers more space
No need of skilled labor
Suitable for cu...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
AIR SEASONING:
Er.PrameshHada,Asst.Professor,civil
Engineeri...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
AIR SEASONING:
Er.PrameshHada,Asst.Professor,civil
Engineeri...
WATER SEASONING
Log of wood is kept completely immerged in stream of
water
Sap, sugar etc are leached out of wood and repl...
ARTIFICIAL SEASONING:
This is quick process of seasoning and moisture content
can be controlled.
o Popular method of artif...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
KILN SEASONING:
This process consists basically of introducing heat.
May be directly, using natural gas and/or electricity...
Advantages of conventional kiln drying include higher
throughput and better control of the final moisture content.
Convent...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Kilns are used because the process speeds up seasoning and i...
Compartmental kiln
A compartment kiln is a single enclosed container or
building, etc.
Timber is stacked as described abov...
Solar kiln
A solar kiln is a cross between kiln drying and air drying.
These kilns are generally a greenhouse with a high-...
PRESERVATION OF TIMBER:
To prevent the probable defects of timber due to fungi, insects,
alternate heating and cooling tim...
Tarring : (coating)
•Timber surface is coated with hot coal tar with brushes
•Coal tar has unpleasant smell and appearance...
Painting:
Paints are good preservatives
Form thin layer in the surface of timber
Thin surface acts as barrier for defectiv...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Abel’s process:
Timber surface is cleaned and coated with a dilute
solution of sodium silicate
Paste of slaked lime is the...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
BAMBOO – (PROPERTIES AND USES)
Bamboo, like true wood, is a natural composite material with
a high strength-to-weight rati...
Can be cut and laminated into sheets and planks(like
board,plyboard).
Bamboo intended for use in construction should be
tr...
Bamboo was treated with borax and boric acid as a fire retardant
and insecticide and bent in the required shape.
The bambo...
WOOD BASED PRODUCTS
1. Veneers
Veneering is the primary process of manufacturing
woods.
Prepared by slicing and sawing of ...
2. Plywood
Is a manufactured wood panel from the family of
manufactured boards (such as medium-density
fibreboard (MDF), p...
PLYWOOD
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepar...
3. BATTEN BOARD
Is a solid block with core of sawn thin wood
The Thickness of core is about 20mm to 25mm
Total thickness o...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
4. LAMIN BOARD
Consist of core of strips each not exceeding 7 mm in
thickness.
These strips are joined together with two f...
IMPREG TIMBER /IMPREGNATED TIMBER
Timber which has been made flame-resistant, fungi-
resistant, or insect-proof by forcing...
COMPREG TIMBER
Processed wood whose cells are impregnated with a resin and
compressed, to reduce shrinking and swelling an...
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
Er.PrameshHada,Asst.Professor,civil
EngineeringDepartment,nec
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Timber civil engineering material - asst. proff. pramesh hada

Timber - Civil Engineering Material - for Civil Engineering Students

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Timber civil engineering material - asst. proff. pramesh hada

  1. 1. CIVIL ENGINEERING MATERIAL CHAPTER 7.0 TIMBER (IMP FOR 7 – 15 MARKS) Prepared By: Er. Pramesh Hada MSC in Urban Planning B.E In Civil (Asst. Professor), Civil Engineering Dept. Nepal Engineering College
  2. 2. TIMBER Timber : Sources, Types, Classification, Characteristics, Advantages & Uses. Growth & Structure of Exogenous Plants Defects in Timber (pu ) Characteristics of Common Timber trees Seasoning of Timber :Air, Water, Kiln, Chemical, Electrical & Boiling (pu) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Electrical & Boiling (pu) Preservation of Timber Properties and Uses of Bamboo Wood Based Products – Veneer, Plywood, Boards, Laminated Boards etc. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  3. 3. TIMBER •Is one of the important construction materials. •Used as structural elements in buildings, widely for doors, windows and partitions and find large use through secondary wood products like plywood, particle boards and laminated boards, etc. •Wood Which is useful for engineering or Other structural Purpose is called “Timber” •Mostly uses timber – plywood,Posts et. in Formwork in Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec •Mostly uses timber – plywood,Posts et. in Formwork in RCC,RBC etc. •Both hard as well as soft woods are in use. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  4. 4. • When tree has been cut down and its stem and branches are roughly converted into pieces of suitable length, then it is known as Rough Timber. • When roughly converted timber is further sawn and converted into commercialized the planks,battens, posts etc is called converted Timber. (Planks – board,plyboard,woodboards), (battens-Partition, Roofing, something to hold) Mostly Timber used in load bearing Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec TIMBER Mostly Timber used in load bearing structure is called structural timber Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  5. 5. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  6. 6. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  7. 7. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  8. 8. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  9. 9. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  10. 10. PROPERTIES OF TIMBER/WOOD Physical Properties : 1. Density - light — very light: density less than 550 kg/m3, eg. bamboo - moderately heavy: density 550 kg/m3 — 750 kg/m3, eg. deodar - heavy-very heavy: density greater than 750 kg/m3, eg. Sal 2. Bulk Density - Defined as the mass of many particles of the material divided by the total volume they occupy. - Depends on air voids present in wood. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec divided by the total volume they occupy. - Depends on air voids present in wood. 3. Moisture Movement - Wood is liable to shrink or swell with the movement of moisture. (increase or decrease) 4. Shrinkage : - Is a Reduction in linear and volumetric dimension due to drying of moisture. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  11. 11. 5. Swelling (Increase in size) - It is increase in linear and volumetric dimension on absorbing moisture. 6. Sound conductivity - Has high Sound Conductivity - Sound velocity in wood is greater than others. PROPERTIES OF TIMBER/WOOD Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec 7. Thermal Conductivity - Has very low thermal conductivity. - so uses for maintain heat temperature in rooms. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  12. 12. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  13. 13. MECHANICAL AND THERMAL PROPERTIES OF TIMBER/WOOD: As wood is natural material there is different mechanical properties for different wood Mechanical properties are governed by soil type, climate and other factors. Properties affected by specific gravity, moisture content, knots and other defects. Wood can’t resist fire and burnt easily. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Wood can’t resist fire and burnt easily. It will be better to take precautions to save timber structure from thermal action Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  14. 14. CHARACTERISTICS OF GOOD TIMBER (PU 2010) Uniform color, strong, durable and workable Straight and compacted fibers Fresh cut surface : sweet smelling Struck: clear ringing sound Relatively heavier Free from all types of defects and disease of timber like knots. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec knots. Planning surface: bright appearance with silky. Sawing: Cut with a saw - not clogging (clogging -Become or cause to become obstructed) Firm adhesion of fibers and compacted medullary rays Well seasoned Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  15. 15. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Fibers in timber Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Defects of Timber Sawing
  16. 16. ADVANTAGES OF TIMBER: (PU 2011) availability: source and transportation strength: light weight and higher strength easy to handle and planed easily joining: simple Repair and Modification: Easy superior, thermal insulation, sound and electrical resistive uses: furniture and decorative purpose Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec uses: furniture and decorative purpose strong and flexible corrosion resistance: excellent higher shock and impact strength . Quick and easy to build. Cheaper than other types of building materials. Easy to heat and cool depending on the weather. More eco-friendly than other materials Can last many years if proper maintenance is carried out. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  17. 17. USES OF TIMBER It is mainly used for following categories of works (i) It is used for construction purposes including building construction, houseposts, beams, rafters, bridges, piles, poles etc. (ii) It is used for furniture and cabinet making. (iii) Used for door and window frames. iv) Uses for Formwork, scaffolding etc, iv) It is also used for heavy packing cases such as Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec iv) It is also used for heavy packing cases such as machinery and similar stores. (v) It is used for manufacturing agricultural implements and tool handles. (vii) It is used for manufacturing veneers, plywoods, boards etc. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  18. 18. HOUSEPOSTS Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec SCAFFOLDING
  19. 19. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  20. 20. DISADVANTAGES OF TIMBER: (PU2011) Defects in timber can reduce the life of wood. Affected by relative humidity, fungi, insects. Modification of general arrangement drawings if based on masonry construction Transportation and carriage access Exposure to weather before enclosed Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Exposure to weather before enclosed vulnerability to decay of timber when exposed to excessive moisture. If left untreated, timber become water logged and crack or chip. Timber is more susceptible to fire than other building materials unless treated and maintained. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  21. 21. Wood is a product obtained from the tree. In simple classification of tree, it can be classified as: 1. Standing timber - if a tree is living then the timber is termed as Standing Timber. 2. Rough timber - if a tree is fallen then the timber is termed as Rough timber. 3. Converted timber - If a tree is modified into desired TYPES OF TIMBER/WOOD Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec 3. Converted timber - If a tree is modified into desired size and shape then the timber is termed as Converted timber. on the basis of mode of growth , the types of trees are : 1. Endogenous Tree 2. Exogenous Tree Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  22. 22. 1. ENDOGENOUS TREE Trees grow in inward direction with the addition of fibrous (like of jute) layer at tip portion, i.e the growth is longitudinal. Trees are hollow at the core and have flexible stem. e.g- Bambo, coconut, Sugarcane etc. For construction purpose only bamboo can be used. Are very flexible due to which they are not generally used for construction material. 2. EXOGENOUS TREE Trees increase in bulk by growing outwards and distinct consecutive rings are formed in the horizontal section of such Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec consecutive rings are formed in the horizontal section of such trees. These rings are called annual rings, because one such ring added every year, such trees grow bigger in diameter as well. Life of trees can be find by counting the annual rings. e.g – Sisham, Sal, Pine etc. Timber from these suitable for construction purpose These are further classified as 1. Deciduous tree 2. Coniferous tree Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  23. 23. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  24. 24. EXOGENOUS TREE Deciduous tree Are characterized by flat and broad leaves which fall in autumn season and new one appear in spring season Hard wood is obtained by such tree which can be used for superior structural and engineering work. e.g – Sal, Sisham, Teak etc. Coniferous tree Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Coniferous tree Trees are characterized by needle shaped thin leaves which are evergreen Trees bear conical shaped fruits and yield resins ( viscous substance ) Soft variety of woods are obtained Used is general constructional purpose - e. g Pine, deodar etc. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  25. 25. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  26. 26. DIFFERENCE BETWEEN HARD WOOD AND SOFT WOOD (CHARACTERISTICS) Aspects hard wood soft wood Annual rings Indistinct Clearly distinct Medullary rays Distinct indistinct Color Dark Light Strength Strong: tens, comp, shear Strong: direct pull Weak: shear Structure Non resinous Resinous and split easily Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Structure Non resinous Resinous and split easily Weight Heavy Light Uses Structural purpose Aesthetic and light structural purpose Sources Deciduous Conifers/evergreen trees Branches Less branches More branches Example Sal, teak, deodar, shisam Pine, chir, kail etc Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  27. 27. SISHAM TREES Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  28. 28. SAL TREE Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  29. 29. TEAK WOOD Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  30. 30. PINE TREES Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  31. 31. DEODAR TREES Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  32. 32. GROWTH OF A TREE Roots of the tree suck a solution of salts from the soil in spring season. Salts are food for the tree and roots transmit the same through the trunk of tree to its branches and leaves. Solution of salts looses some of the moisture because of evaporation and absorbs carbon dioxide from the air. This action in the presence of sun makes the solution a bit viscous. This transformed viscous solution is known as sap. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec viscous. This transformed viscous solution is known as sap. Viscous sap descends below the bark and leaves a thick layer in autumn. Layer of sap left below the bark gets transformed to wood and is known as cambium layer. A fresh layer is thus added on the outside of the tree every year forming a new annual ring. The new ring represents a year’s growth of tree. Medullary rays carry the sap from below the bark to the interior thereby nourishing the tree. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  33. 33. STRUCTURE OF A EXOGENEOUS TREE (PU 2009,2010) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec • Pith/Medulla/Core •Heart wood •Sap wood •Cambium Layer •Inner Bark •Outer Bark •Medullary rays Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  34. 34. Pith/ medulla/core: It is first formed portion of trees. It consist entirely cellular tissues and nourishes the plant in young age. It is found as dead part of the trees incase of matured trees and decayed. Annual rings: Grows extra layer around the circumference of the trees per year Circular concentric rings STRUCTURE OF A EXOGENEOUS TREE Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Circular concentric rings Each rings indicates the age of tree in year Heart wood: Annual rings around the pith at the innermost central portion of the tree section Strong, durable and compact part of trees Darker in color Best part of trees in engineering views Imparts rigidity to the trees Doesn’t take active part in growth of trees Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  35. 35. Sap wood: Outer annual rings between heart wood and the cambium layer Light in color and weight as well Indicates recent growth and contains sap (Sap = A watery solution of sugars, salts, and minerals that circulates through the vascular system of a plant ) Annual rings of sap wood are less sharply defined in comparison to heart wood Takes active part in growth of trees Cambium layer: Thin layer of sap between sap wood and inner bark It indicates sap which has yet not been converted into sap wood STRUCTURE OF A EXOGENEOUS TREE Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec It indicates sap which has yet not been converted into sap wood If barks are removed and get exposed, the cell cease and death Inner bark: Inner layer covering the cambium layer Protect cambium layer from any injury Outer bark: A protective layer, outer skin covering the trees Contains cracks and fissures sometimes Consists of cells of wood fibers and is known as cortex Medullary rays: (Pit rays ) Radial fibers extending from pith to cambium layer Hold the annual rings of heart wood and sap wood together Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  36. 36. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  37. 37. MICROSTRUCTURE OF WOOD Structure of wood apparent only at great magnifications is called microstructure. If study through microscope, it becomes evident that wood consists of living and dead cell of various shape and sizes Living cell consists Membrane (consists cellular tissue and cellulose) Protoplasm (granular and transparent, viscous vegetables, protein composed of carbon, hydrogen, oxygen, nitrogen and sulphur) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec sulphur) Sap (differ from protoplasm by presence of phosphorous and shape is oval) Types of cell on the basis of their function: conductive cells mechanical cells storage cells Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  38. 38. Conductive cells: serves to transmit nutrients from roots to the branches and leaves Mechanical Cells: these cells are elongated, thick walled and having tightly interconnected narrow interior cavities - imparts strength to the wood Storage Cell: serves to store and transmit nutrients to MICROSTRUCTURE OF WOOD Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Storage Cell: serves to store and transmit nutrients to the living cells in horizontal direction and they are usually located in the medullary rays Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  39. 39. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Resinous wood Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  40. 40. DEFECTS IN TIMBER (PU 08,09,10,12,13) Defects are either due to growing phases of tree or defect occurring after cutting trees Defects reduce the usefulness of wood as aesthetic appearance as well as strength 1. Heart Shake - This defect usually occurs in over matured trees due to shrinkage of heart wood - These cracks are mostly confined to heart wood portion and diminishing towards outward. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec and diminishing towards outward. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  41. 41. 2. Star Shake - It is confined in the outward portion and diminishing towards center. - It occurs due to frost action and strong heat of sun. - It is the most serious defect because it tends to separate single log into small pieces. DEFECTS IN TIMBER Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec 3. Radial Shake - These are radial cracks extending from centre towards bark . - These are similar to star shake but are irregular and numerous. - It occurs due to drying of sap or moisture . Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  42. 42. 4. Cup or Ring Shake - Is the separation of tissue along annual rings - If the shake is whole round the annual ring then it is called ring shake and if it is half way round the ring then it is called cup shake. - It is due to unequal seasoning and change in humidity. DEFECTS IN TIMBER Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec 5. Rind Gall - Is the curved irregular swelling on surface. - Due to development of new sap layer on wound left after branches have been irregularly cut. - New layer fails to unite with old one and decay starts from that point Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  43. 43. 6. Knots - This defect occurs due to formation of annual rings at right angles to surface and also due to twisting of fibers. - The roots of the branches yet embedded(Enclosed firmly) by the tissue and knots are formed - Knots reduce the aesthetic value and effects tensile strength - Knots may be round or oval shaped DEFECTS IN TIMBER Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  44. 44. 7. Twisted fibers - This defect occurs due to wind velocity constantly turning trees in one direction only. DEFECTS IN TIMBER Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec 8. End Splits - Occurs only at the ends of log due to exposed conditions during seasoning. - May be prevented by painting the ends of log or covering with metallic cap. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  45. 45. 9. Druxiness and Foxiness (Druxiness is a term that is defined as a disease that is found in timber or wood. It is caused or brought about by a wound located in the layer known as the cambium which is attacked by fungus.) (Foxiness is caused due to poor ventilation during storage or due to over maturity of the tree). DEFECTS IN TIMBER Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec - These are stains or patches on the surface of timber which destroy the appearance and may cause decay of timber - Stain may be in form of white patches or mottled reddish colour. (stains - A soiled or discolored appearance) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  46. 46. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  47. 47. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  48. 48. SEASONING OF TIMBER: (PU 09,10,11) Wood is hygroscopic material, dry wood absorbs moisture from surroundings Freshly cut wood may contains more than 50% water in the form of sap and moisture After removal of such water from wood then it can be used in diff. engineering works Thus drying process of timber is known as seasoning of timber Moisture must be extracted during seasoning under controlled conditions as nearly as possible at a uniform rate from all parts Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec conditions as nearly as possible at a uniform rate from all parts of the timber If the drying is irregular, the shrinkage of timber will also be irregular and it will set up internal stresses between the fibers Moisture content in wood may be: Free moisture: present in cell cavities (major part) Bound moisture: present in cell wall ( associated with the body of timber) o Free moisture/ water evaporated first and the point at which cell cavities no longer contain free water is known as fiber saturation point. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  49. 49. FOLLOWING ARE THE DIFFERENT OBJECTIVES OF SEASONING: Timber to burn readily, if used as fuel Decreased the weight of timber: easy handling and low cost Impart hardness, stiffness, strength, better electrical resistance. (stiffness - hard to bend) To increase resisting power of timber against the cause of defects Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec cause of defects To maintain the shape and size of the component of the timber To make it fit for painting and other treatment For effectively gluing and joining To reduce the shrinkage, warping, twisting (shrinkage - becoming less or smaller) (Warping - Bend out of shape, as under pressure or from heat) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  50. 50. METHODS OF SEASONING OF TIMBER: Natural seasoning Air seasoning/ drying Water seasoning Artificial seasoning Air seasoning: Method used with the timber stacked in the open air. It requires the following: Stacked stable and safely with horizontal spacing of at Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Stacked stable and safely with horizontal spacing of at least 25 mm. Ends of boards sealed by using a suitable sealer or cover to prevent too rapid drying out via the end grain. The stack raised well clear of the ground, vegetation, etc to provide good air circulation and free from rising damp, frost, etc. Over head cover from effects of direct sunlight and driving weather. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  51. 51. AIR SEASONING: This method is economical one Takes 2 to 4 years Covers more space No need of skilled labor Suitable for cut of sawn planks pieces of wood not for log of wood Timber can stack either horizontally or vertically Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Timber can stack either horizontally or vertically Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  52. 52. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec AIR SEASONING: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  53. 53. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec AIR SEASONING: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  54. 54. WATER SEASONING Log of wood is kept completely immerged in stream of water Sap, sugar etc are leached out of wood and replaced by water Then log is kept out of water after 2 to 4 weeks and placed in air Quick process and also remove organic matters/ Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Quick process and also remove organic matters/ materials Elasticity may reduced and make timber brittle Boiling of timber in water is another rather quick process Takes long time to be dried but less than air seasoning Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  55. 55. ARTIFICIAL SEASONING: This is quick process of seasoning and moisture content can be controlled. o Popular method of artificial seasoning is KILN SEASONING. Reason for carrying artificial seasoning are : Shrinkage, cracking and warping are minimized Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Drying is controlled and no chances for the attack of fungi and insects Drying surface is even and uniform Reduced duration of seasoning Desired moisture content can be attainable (shrinkage – becoming less or smaller) (warping - Bend out of shape, as under pressure or from heat) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  56. 56. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  57. 57. KILN SEASONING: This process consists basically of introducing heat. May be directly, using natural gas and/or electricity or indirectly, through steam-heated heat exchangers, although solar energy is also possible. In the process, deliberate control of temperature, relative humidity and air circulation is provided to give conditions at various stages (moisture contents or times) of drying the timber to achieve effective drying. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec times) of drying the timber to achieve effective drying. Timber is stacked in chambers, called wood drying kilns, which are fitted with equipment for manipulation and control of the temperature and the relative humidity of the drying air and its circulation rate through the timber stack. Provides a means of overcoming the limitations imposed by erratic(inconsistent) weather conditions. Almost all commercial timbers of the world are dried in industrial kilns. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  58. 58. Advantages of conventional kiln drying include higher throughput and better control of the final moisture content. Conventional kiln and solar drying both enable wood to be dried to any moisture content regardless of weather conditions. For most large-scale drying operations solar and conventional kiln drying are more efficient than air drying. Compartment-type kilns are most commonly used in timber companies. KILN SEASONING: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec companies. A compartment kiln is filled with a static batch of timber through which air is circulated. In these types of kiln, the timber remains stationary. Drying conditions are successively varied from time to time in such a way that the kilns provide control over the entire charge of timber being dried. Method is well suited to the needs of timber companies, which have to dry timbers of varied species and thickness. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  59. 59. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Kilns are used because the process speeds up seasoning and it can be used to accurately control the moisture content of the wood. Wood is carefully stacked inside the brick kiln. Water is heated and the resulting steam allowed to enter the kiln, circulating inside and around the wood boards. Over time, the amount of steam (humidity) is reduced until the wood has the desired moisture content. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  60. 60. Compartmental kiln A compartment kiln is a single enclosed container or building, etc. Timber is stacked as described above and the whole stack is seasoned using a program of settings until the whole stack is reduced to the moisture content required. Progressive: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Progressive: A progressive kiln has the stack on trolleys that ‘progressively’ travel through chambers that change the conditions as it travels through the varying atmospheres. (trolleys - An wheeled vehicle that runs on rails and is propelled by electricity) The advantage of this system, although much larger, has a continuous flow of seasoned timber coming off line. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  61. 61. Solar kiln A solar kiln is a cross between kiln drying and air drying. These kilns are generally a greenhouse with a high- temperature fan and either vents or a condensing system. Solar kilns are slower and variable due to the weather, but are low cost. Other seasoning of Timber are Boiling or Steam seasoning Submersion in boiling water or the application of steam speed the drying of wood. This method is said to cause less shrinkage "...but it is expensive to use, and reduces the Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec shrinkage "...but it is expensive to use, and reduces the strength and elasticity of the timber." Chemical or salt seasoning Salt seasoning is the submersion of wood in a solution of urea, sodium nitrate or sodium chloride, all of which act as dehydrating agents. Then the wood is air dried. Electrical seasoning Electrical seasoning involves running an electrical current through the timber causing heat to build up drying the wood. This method is expensive but is fast and uniform quality. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  62. 62. PRESERVATION OF TIMBER: To prevent the probable defects of timber due to fungi, insects, alternate heating and cooling timber must be preserved in order to increase the life span of timber, make durable. Following are the various methods of preservation : Charring: Very old method, no preservatives are used Surface to be charred is kept wet for about half an hour and burnt up to 15mm depth over a wood fire The charred portion is then cooled by water Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec The charred portion is then cooled by water This burnt layer doesn’t affected by moisture, fungi etc Adopted for lower ends of posts for fencing, telephone etc (Charring: Burn to charcoal ) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  63. 63. Tarring : (coating) •Timber surface is coated with hot coal tar with brushes •Coal tar has unpleasant smell and appearance •Coal tar makes timber unsuitable for painting •Adopted for frames of doors and windows, rough timber work etc •Coal tar is fire-resistant. ( Tar - It can be produced from coal, wood, petroleum. It is black, and a mixture of hydrocarbons and free carbon. ) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  64. 64. Painting: Paints are good preservatives Form thin layer in the surface of timber Thin surface acts as barrier for defective environmental factors Creosoting: Timber surface coated with creosote oil Creosote oil is obtained by distillation of tar (distillation - process of purifying a liquid by boiling it and condensing its vapors) Steps are: Timber are thoroughly seasoned and dried PRESERVATION OF TIMBER: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Timber are thoroughly seasoned and dried Placed well seasoned wood in air tight chamber Air is pumped out from chamber Creosote oil is then pumped under high pressure of 0.7-1.0N/mm2 and temperature of about 500C After 1 to 2 hrs, when timber has sufficiently absorbed creosote oil, it is taken out of chamber Creosote oil is antiseptic or it is poisonous to the wood-attacking fungi Creosote oil: black or brown liquid and weakly affected by water Unpleasant odour and having low wood-penetrating ability to the extent of 1mm to 2mm only It produces undesirable color in timber Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  65. 65. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  66. 66. Abel’s process: Timber surface is cleaned and coated with a dilute solution of sodium silicate Paste of slaked lime is then applied and finally, a concentrated solution of silica soda is applied on the timber surface This process is quite satisfactory in making the PRESERVATION OF TIMBER: Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec This process is quite satisfactory in making the timber fire- resistant Fire proofing of timber: Timber can’t be made fire proof but some chemical treatment may reduce the fire attack towards the timber Soaking of timber in ammonium sulphate, ammonium chloride, zinc chloride etc improves the fire resisting capacity of timber. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  67. 67. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  68. 68. BAMBOO – (PROPERTIES AND USES) Bamboo, like true wood, is a natural composite material with a high strength-to-weight ratio useful for structures. In China and India, bamboo was used to hold up simple suspension bridges, either by making cables of split bamboo or twisting of sufficiently pliable(workable) bamboo together. Bamboo has also long been used as scaffolding; the practice has been banned in China for buildings over six storeys, but is still in continuous use for skyscrapers in Hong Kong. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec still in continuous use for skyscrapers in Hong Kong. In Japanese architecture, bamboo is used primarily as a supplemental and/or decorative element in buildings such as fencing, fountains, grates and gutters, largely due to the ready abundance of quality timber. Notes (Grates - A barrier that has parallel or crossed bars blocking a passage but admitting air.) (Gutters - A channel along the eaves or on the roof; collects and carries away rainwater ) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  69. 69. Can be cut and laminated into sheets and planks(like board,plyboard). Bamboo intended for use in construction should be treated to resist insects and rot. The most common solution for this purpose is a mixture of borax and boric acid. Bamboo has been used as reinforcement for concrete in BAMBOO – (PROPERTIES AND USES) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Bamboo has been used as reinforcement for concrete in those areas where it is plentiful, though dispute exists over its effectiveness in the various studies done on the subject. Bamboo does have the necessary strength to fulfil this function, but untreated bamboo will swell with water absorbed from the concrete, causing it to crack. Several procedures must be followed to overcome this shortcoming. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  70. 70. Bamboo was treated with borax and boric acid as a fire retardant and insecticide and bent in the required shape. The bamboo sections were joined with reinforcement bars and concrete mortar to achieve the necessary lengths BAMBOO – (PROPERTIES AND USES) Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  71. 71. WOOD BASED PRODUCTS 1. Veneers Veneering is the primary process of manufacturing woods. Prepared by slicing and sawing of wood in thin sheets of 0.4mm to 6mm. Are of superior Quality. Used in manufacturing ply woods, battens, lamin Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Used in manufacturing ply woods, battens, lamin boards. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  72. 72. 2. Plywood Is a manufactured wood panel from the family of manufactured boards (such as medium-density fibreboard (MDF), particle board (chipboard), etc.) made from thin sheets of wood veneer. Prepared by gluing together odd number of veneers with grain direction of core block at right angle to adjacent veneer or ply. WOOD BASED PRODUCTS Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec veneer or ply. Are used in making partition, furniture, ceiling, doors, paneling wall, Formworks for concrete. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  73. 73. PLYWOOD Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  74. 74. 3. BATTEN BOARD Is a solid block with core of sawn thin wood The Thickness of core is about 20mm to 25mm Total thickness of board is about 50mm Is Light and strong Do not crack or split easily Uses: partition wall, furniture, shutters, packing case Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Uses: partition wall, furniture, shutters, packing case Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  75. 75. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  76. 76. 4. LAMIN BOARD Consist of core of strips each not exceeding 7 mm in thickness. These strips are joined together with two face veneers. Lamin board are used for furniture, partition, doors, windows, ceilings,etc. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  77. 77. IMPREG TIMBER /IMPREGNATED TIMBER Timber which has been made flame-resistant, fungi- resistant, or insect-proof by forcing into it under vacuum or pressure a flame retardant or a fungal or insect poison. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  78. 78. COMPREG TIMBER Processed wood whose cells are impregnated with a resin and compressed, to reduce shrinking and swelling and to increase density and strength. Compreg is a very special wood composite material with exquisite mechanical properties. Compreg indicates that it is both impregnated and compressed. Used in applications where long durability, hardness, and dimensional stability is required e.g. gears, rolls and wear Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec dimensional stability is required e.g. gears, rolls and wear strips of industrial conveyors, woodworking machine tables. Regardless of its hardness, it is comparatively easy to machine, which makes it an excellent choice for manufacturers of exclusive woodworking products. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec
  79. 79. Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec Er.PrameshHada,Asst.Professor,civil EngineeringDepartment,nec

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Timber - Civil Engineering Material - for Civil Engineering Students

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