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UNIT – II
CONSTRUCTION PRACTICES
SYNOPSIS
 Specification
 Precast Pavements
 Sequence of activities
 Slip Forms
 Site clearance, Marking
 Scaffoldings
 Damp Proof Course, Weathering
 Fabrication & Erection of Steel
Course
 Masonry
 Flooring
 Roofing
 Construction Joints
 Foundation
Trusses
 Air Conditioning
 Acoustics
 Fire Protection
 Centering & Shuttering
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
Sequence of Activities to be done in Construction
 Excavation
 Plastering
 Concrete in Foundation
 Pointing
 Soiling
 Doors
 Damp Proof Course(DPC)
 Windows
 Masonry Work
 Wood Work
 Lintel
 Iron Work
 Reinforced Cement Concrete
 White Washing
 Flooring
 Colour Washing
 Roofing
 Painting
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
Stone Masonry
Based on the arrangement of the stones in the construction
and degree of refinement in the surface finish.
 Rubble Masonry
 Ashlar masonry
 Coursed rubble
 Ashlar fine
 Uncoursed Rubble
 Ashlar Rough – tooled
 Dry Rubble
 Ashlar Rock or quarry face
 Polygonal Rubble
 Ashlar Chamfered
 Flint Rubble
 Ashlar Block – in - course
Brick Masonry
Brick masonry is unified mass obtained by systematic
arrangement of laying bricks and bonding them together with
mortar.
 Stretcher bond
 Header bond
 English bond
 Flemish bond
 Garden wall bond
 Raking bond
 Dutch bond
 Brick on edge bond
 English cross bond
 Facing bond
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
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
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.
 Mud & Murram
 Flag – Stone or Stone
 Brick
 Timber
• Rubber
• Linoleum
• Cork or Cork tiles
 Cement concrete & Concrete
• Magnesite
 Mosaic
• Glass
 Terrazzo
 Granolithic
 Tiled
• Marble
• Plastic or PVC
• Asphalt
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
Pitched Roof or Sloping Roof
 Single Roof
Lean – to Roof
Couple Roof
 Triple – membered or Framed or
Trussed Roof
King post roof truss
Couple close Roof
Collar beam Roof
Queen post roof truss
Collar & Scissors Roof
Combinations of both truss
Double or Purlin Roof
Mansard roof truss
Truncated roof truss
Belfast roof or bow string or latticed
roof truss
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.
Types of Foundation
Open or Shallow foundation
Wall footing
Isolated footing
Combined footing
Inverted arch footing
Continuous footing
Cantilever footing
Grillage footing
Raft foundation
Pile Foundation
Function
Bearing piles
Friction piles
Screw piles
Compaction piles
Uplift piles
Batter piles
Sheet piles
Material & Composition
Cement concrete piles
Pre cast concrete piles
Cast in situ concrete piles
Timber piles
Steel piles
Sand piles
Composite piles
Well Foundation or Caisson
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
Construction 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
Contraction joint
 Plastic, drying shrinkage, concrete shrinks
 Avoid cracks – joints provided 5 -10 m
 Dummy or control joints
 Unreinforced floors and pavements
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
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
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
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
Slip forms
Essential parts of slip forms are as follows
Sheathing
Wales or ribs
Yokes
Working platform or deck
Suspended scaffolding
Lifting devices
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.,
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
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
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
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
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
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
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
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
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
Domes
Semi – spherical or semi elliptical in
shape
Used as roof structure – material stone,
Types of domes
brick or concrete
Spherical domes
Supported on regular or circular polygon
Cylindrical domes
shaped walls
Rectangular domes
Certain height, diameter ratios, small
Triangular domes
thickness
Square domes
Used in monumental work(circular,
Intersecting
hexagonal shape)
curved barrel domes
Domes can be either smooth shell domes
or ribbed domes
double
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
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
Acoustical defects
Formation of echoes
Reverberation
Sound foci & dead spots
Insufficient loudness
Exterior noise nuisance or out door noise effects
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
Thank you