1. Construction Techniques, Equipment and Practice
UNIT – II
CONSTRUCTION PRACTICES

2. SYNOPSIS Precast Pavements Slip Forms Scaffoldings
Fabrication & Erection of Steel Trusses
Air Conditioning
Acoustics
Fire Protection
Centering & Shuttering
Specification
Sequence of activities
Site clearance, Marking
Damp Proof Course, Weathering Course
Masonry
Flooring
Roofing
Construction Joints
Foundation

3. Specification
Specifications are statements which describe the nature and class of work, materials to be used, labour to be employed, method of work, precautions to be taken, quality of workmanship etc.,
Contract specification
General specification
Detailed specification
Guide specification
Manufacturer’s specification

4. Sequence of Activities to be done in Construction
Excavation
Concrete in Foundation
Soiling
Damp Proof Course(DPC)
Masonry Work
Lintel
Reinforced Cement Concrete
Flooring
Roofing
Plastering
Pointing
Doors
Windows
Wood Work
Iron Work
White Washing
Colour Washing
Painting

5. Masonry
It is used to indicate the art of building the structures either in stones or bricks.
Masonry classification
Stone masonry
Brick masonry
Hollow block concrete masonry
Reinforced masonry
Composite masonry

6. Stone Masonry Based on the arrangement of the stones in the construction and degree of refinement in the surface finish.
Rubble Masonry
Coursed rubble
Uncoursed Rubble
Dry Rubble
Polygonal Rubble
Flint Rubble
Ashlar masonry
Ashlar fine
Ashlar Rough – tooled
Ashlar Rock or quarry face
Ashlar Chamfered
Ashlar Block – in - course

8. Brick Masonry Brick masonry is unified mass obtained by systematic arrangement of laying bricks and bonding them together with mortar.
Raking bond
Dutch bond
Brick on edge bond
English cross bond
Facing bond
Stretcher bond
Header bond
English bond
Flemish bond
Garden wall bond

10. Composite Masonry
Sometimes the facing and backing of a wall are constructed with different classes of masonry or of different materials.
Following are the usual combination
Facing of ashlar masonry and backing of rubble masonry brickwork
Facing of stone slabs and backing of concrete or brickwork
Facing of brickwork and backing of rubble masonry
Facing of brickwork and backing of cement concrete
Facing of brickwork and backing of hollow cement concrete blocks

12. Reinforced Masonry
It’s a wall material. Beam, slabs have been built but with exception of deep wall beams.
It does not require shuttering and expensive element of concrete.
It lies in walls subject to bending perpendicular to the wall beams.
It combines flexibility of form with good finish and frequently a large cost saving compared with reinforced concrete.
Reinforced masonry is thus a cheap, durable, fire – proof, easy to construct and in most cases it results in the increase of floor space due to adoption of brickwork of lesser thickness.
Reinforced Masonry Walls
Masonry Reinforced Columns
Reinforced Masonry Lintels
Reinforced Masonry Slab

14. Flooring Floors are the horizontal elements of a building structures which divide the building into different levels for the purpose of creating more accommodation within a restricted space one above the other and provide support for the occupants, furniture and equipment of a building.
Rubber
Linoleum
Cork or Cork tiles
Magnesite
Glass
Marble
Plastic or PVC
Asphalt
Mud & Murram
Flag – Stone or Stone
Brick
Timber
Cement concrete & Concrete
Mosaic
Terrazzo
Granolithic
Tiled

16. Roofing Roof is the uppermost part of a building which is supported on structural members and covered with a roofing material. The main function of a roof is to enclose the space or building and to protect the same from the damaging effects of weather elements such as rain, wind, heat, snow, etc., A good roof also increases the life of the building.
Pitched or Sloping Roofs
Flat or Terrace Roofs
Shell or Curved Roofs
Domes

18. Pitched Roof or Sloping Roof
Triple – membered or Framed or Trussed Roof
King post roof truss
Queen post roof truss
Combinations of both truss
Mansard roof truss
Truncated roof truss
Belfast roof or bow string or latticed roof truss
Single Roof Lean – to Roof Couple Roof Couple close Roof Collar beam Roof Collar & Scissors Roof Double or Purlin Roof

20. Foundation
The structure which is in direct contact with the ground. It transfers the load of the structure to the soil below so as to avoid over – loading of the soil beneath.
It prevents the differential settlement by evenly loading the substrata.
It provides a level surface for building operations.
It also increases stability of structure by taking the structure deep into the ground.
Foundations are generally built of bricks, stones, concrete, steel, etc.,
The selection of material and type of foundation depends upon the type structure and the nature of underlying soil.
Foundations should be designed to be capable of being constructed economically and without risk of protracted delays.

21. Types of Foundation Open or Shallow foundation Wall footing
Isolated footing
Combined footing
Inverted arch footing
Continuous footing
Cantilever footing
Grillage footing
Raft foundation

25. Pile Foundation Function Material & Composition Bearing piles
Friction piles
Screw piles
Compaction piles
Uplift piles
Batter piles
Sheet piles
Well Foundation or Caisson
Material & Composition
Cement concrete piles
Pre cast concrete piles
Cast in situ concrete piles
Timber piles
Steel piles
Sand piles
Composite piles

28. Construction Joints
Construction joints are provided construction stopped at end of day
Proper bond between old work & new one(necessary to ensure)
Joints may be horizontal or vertical
In construction of large concrete members airfield pavements, road pavements, factory floors, residential floors, columns in framed structure cannot place concrete in one operation
Joints are left between subsequent concreting operation
Types of joints are
Construction joint
Expansion joints
Contraction joints

29. Construction joint Expansion joint Temporary joint
Position should be planned and concrete should be placed in one operation.
Walls & columns – horizontal, vertical
Beams & slabs – minimum shear
Appearance disturbed
Expansion joint
Volume changed
Floor, roof – joint not necessary for small building
Large building – joint necessary(2-5cm)
Maximum temperature : day : expansion
Minimum temperature : night : contraction

30. Contraction joint Plastic, drying shrinkage, concrete shrinks
Avoid cracks – joints provided m
Dummy or control joints
Unreinforced floors and pavements

32. Precast concrete piles
Piles are manufactured in factory & driven into ground. Tampered or parallel
Square, octagonal shaped cast in horizontal forms, round shaped cast in vertical forms
Size 30 – 50cm, length – 18m or more
Reinforcement is used for stress.
Main or vertical reinforcement 20 – 40mm, lateral 5 – 10mm, spacing - 10cm( top, bottom), intermediate - 30cm
Toe : steel shoe

33. Casting
Form work prepared and coated with soap solution or oil to prevent adhesion
Cage of reinforcement is prepared, placed in formwork with cover 50mm
Concrete 1:2:2 or 1:2:4, CA – 10 to 25 mm size
Pour concrete in formwork and consolidated with vibrators
Formwork removed in 3days, remains 7days and then shifted to curing tank for 3 to 4 weeks

34. Advantage
Position of reinforcement not disturbed from original position
Piles can driven under water. Sulphate resistance
Proper control & design is possible while manufacture
Defect of cast is repaired before driven into the ground
More piles are manufactured at convenient place & economical
Pile is smooth while driving it takes load, no wastage of time
High resistance to biological & chemical actions on ground

35. Disadvantage Heavy weight : transport, driven is difficult
Costly extra reinforcement is provided to resist stresses develop during handling & driving
Wastage of material, if long pile is manufactured
Sufficient care should to taken while transport or driving
Piles not available – delay of work occur
Size, length of pile depend on available transport facility

37. Slip forms Essential parts of slip forms are as follows Sheathing
Wales or ribs
Yokes
Working platform or deck
Suspended scaffolding
Lifting devices

38. Operation
Over concrete base, slip form set is assembled and filled with concrete
After setting of concrete, sufficient rigidity in bottom then upward movement started from bottom to top.
Depending upon temperature, properties of concrete lifting rate is 50 to 80mm
Experienced person is employed for movement of slip form while moving
Uses
Vertical structures : economical
Used for piers, chimneys, towers, missile launching bases, water reservoirs, silos, resolving restaurants, etc.,

39. Removal Some factors: amount & nature of dead load
Character & quality of concrete
Shape, span & situation of structure
Temperature of the atmosphere
2-3 days remove formwork – beam sides
10-21 days – between beam, floors
Use rapid hardening cement within 3-4 days formwork can removed
High – alumina cement, takes few hours to remove formwork

41. Scaffolding
Temporary structure gives support to workman, structural material, other appliances, etc.,
Used in building construction, demolition, maintenance & repair works
Erected either one(ordinary works) or both sides of walls(superior works) and heights can adjusted
Components
Planks – supporting men, materials, appliances
Guard boards – working on ledgers level to guard materials
Toe boards – parallel to ledgers for protection

42. Types
Single or bricklayers scaffoldings – BW used in construction, made of bamboos, poles except platform, single standard 1.5 to 2m, spacing 1.2m, ledgers 1.2 – 1.5m, put legs 1.2 – 1.5m
Double scaffolding – stronger, stone work, two rows
Ladder scaffolding – easily assembled, platform supported on brackets, heights can adjusted, used in light works such as exterior walls, paintings, decorations
Cantilever scaffolding – Where standard not possible to fix in ground, busy street, traffic areas, upper storey of tall buildings
Suspended scaffolding – light steel frame construction, maintenance work such as paintings, pointing, distempering, etc., working platform is suspended from roofs by means of wire ropes or chains

43. Steel scaffolding – same as timber scaffolding except wooden members are replaced by steel tubes and rope
Removal
Walls, beams, column sides(low load)
Slabs
Heavy load, girders, beam bottom
Walls, columns, beams sides : 1 – 2 days
Slabs : 3
Beam soffit (under) : 7
Slab upto 4.5 : 7, over 4.5 :14
Beams upto 6 : 14
Arches over 6 : 21

45. Fabrication & Erection of Trusses
Roof trusses : principle rafters, ties, struts, purlin, cleats etc., gusset plates, rivets, bolts
Use of steel trusses proves to economical for span >12m
Steel roof trusses designed should be compression or tension (no bending stress)
Arrangement & size depends upon roof slope, span, loading wind pressure distance
Compression member strut : short to avoid buckling, principle rafter : transverse stresses not larger than 3m & maximum
T section best for principle rafter, channel for struts

46. Small trusses fabricated in factory or workshop & transport to site while large trusses fabricated at the job site
Truss should be arranged to form triangles – truss not deform
Distance not exceed 3m, light roofs – more distance or spacing
Joints or connection of member called nodes or panel points, gusset plates
In rivets, pitch should not less than 3times diameter. L < 7 18mm diameter rivets, L > 7 20mm diameter rivets
Gusset plate thickness 6mm(small) & 10mm(large) roof trusses
Three types of trusses north light roof trusses – factories, workshop, Bow string type trusses – 20m span, arched truss
Small span end of truss fixed, large span one fixed, one end mounted on steel rollers

47. Air conditioning of buildings
Process of treating air to control temperature, humid purity distribution to meet the meet the requirement of conditioned
Classification of air conditioning
Comfort – inside the room(Residential, institution, hospitals)
Industrial – material processing, manufacturing storage etc.,
Steps of air conditioning
Summer - outside temp is above inside temp , cycle of operation involves air cooling, dehumidifying, air distribution & air cleaning
Winter – below, air heating, humidification
Composite - both

48. Principle of comfort air conditioning
Temperature control – comfortable zone for people both in summer & winter
Air velocity control – velocity increases, temperature decreases 6-9m/s
Humidity control – with conditioned air is important, dry air , moisture is added to heated air(summer), moisture extracted from cool air, humidity 40 – 60%
Systems
Central system – one focal point, conditioned air is distributed to all room, less space for installation, maintenance easy, one unit(economical), instead of more unit for every room
Unit system – window
Unitary control – from central to every unit
Combined control –central or self conditioned, central or semi conditioned

49. Frames
In portal frames structural roof members are rigidly connected to column or post for continuous structural member to withstand bending
North light RC portal frames
Span 9m, rafter south facing slope 221/2•, north 60• - 80•
Rafter divided into sections for convenience in casting & transporting
Rafter is bolted together, gutter, purlin to support wood wool slabs
Slabs(insulators) – roof deck covered with north light glazing
Flat RC portal frames monitors
Two span portal type – monitor light provided, made of glazing, open for ventilation
At junction of monitor light & flat roof – large heavy precast reinforced concrete beams are bolted to frame
Serve for fixing roof covering & glazing

50. Domes Types of domes Semi – spherical or semi elliptical in shape
Used as roof structure – material stone, brick or concrete
Supported on regular or circular polygon shaped walls
Certain height, diameter ratios, small thickness
Used in monumental work(circular, hexagonal shape)
Domes can be either smooth shell domes or ribbed domes
Types of domes
Spherical domes
Cylindrical domes
Rectangular domes
Triangular domes
Square domes
Intersecting double curved barrel domes

51. Braced domes Oldest structural form, arch, three dimensional structure
Enclose maximum space with minimum surface & economical in terms of material
Material – high strength alloy(magnesium alloy, aluminum alloys)
Types
Frame or skeleton type – single layer dome
Truss type – double layer dome, extremely rigid provides greater resistance to buckling, suitable for layer spans
Stressed skin type – covering part an integral part of structural system
Framed surface type – bent sheets interconnected along edges to form main skeleton

52. Acoustics
The branch of science which deals with the planning of building or hall with a view to provide best audible sound to the audience
Features of good acoustics
The sound heard must be sufficiently loud in every part of the hall and no echoes should be present
The total quality of speech and music must be changed ie., relative intensities of several components of a complex sound must be maintained
The successive syllables spoken must be clear and distinct
The reverberation should be quite proper ie., neither too low nor too high
There should not be any concentration of sound in any portion of hall
The boundaries should be sufficiently sound proof

53. Acoustical defects Formation of echoes Reverberation
Sound foci & dead spots
Insufficient loudness
Exterior noise nuisance or out door noise effects

54. Fire Protection in Buildings
For important buildings in addition to the use of fire resisting materials and adoption of fire resistant construction, the following general measure of safety have been recommended
Alarm system
Manual alarm system
Automatic alarm system
Fire extinguishing arrangements
Normally operated equipments
Fire hydrants
Automatic sprinkler system
Escape routes

60. Thank you