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2.2 RC components.pdf
1. RC COMPONENTS
BEAM, COLUMN, FLOOR & FLAT ROOF
BQS 502 Construction Technology III
Mohd Arif Marhani
A377
0193105479
Centre of Studies for Quantity Surveying
4. REINFORCED
CONCRETE BEAM
o When floor slab is
cast monolithic with
the beam, the
beams are of the
following shapes:
Deep T-beam, T-
beam, L-beam
(upstand) & L-
beam (downstand)
5. o Horizontal member of a framework, to transfer the loads
imposed on it to the points of support (column or main beam)
o When subjected to loads, will deflect/bend & create:- tension
(bottom); compression (top); & shear at/near the support, or
along its length
o Beams are normally continuous over support, & there will be a
reversal of stress at the point of support, normally compressive
stress and this can be solved by the following methods:
1. Providing compressive reinforcement
2. Deepening the rib by means of a haunch
3. Widening the rib for its full depth
4. Widening the bottom of the rib only to provide a lower
flange
REINFORCED CONCRETE BEAM
8. o Vertical member which transfers the loading of the beam & floor
to the substructure
o When subjected to loads, it will be either :
Squashing/buckling – occurs as a result of the column
material being unable to withstand compressive loading
Bending – occurs when beam fixed rigidly to the column
o Concrete is strong in compression and can be said that if the
compressive strength of the concrete is not exceeded, then no
reinforcement will be required
o BUT, for this to be true, the following conditions must exist:-
column must be short; & cross section of column must be large
o Unfortunately, these do not occur in framed buildings, as a result
bending is induced and the need for reinforcement is necessary
REINFORCED CONCRETE COLUMN
9. o Square
o Rectangular
o L-shaped
REINFORCED CONCRETE COLUMN
Various shapes/sections of
columns
o Round
o Octagonal
o U-shaped
12. REINFORCED CONCRETE FLOOR SLAB
o Definition: horizontal plane to support both live & dead loads,
and safely transfer these loads to beam & column (dividing
element at different levels)
o There are many types of floor structures:
In-situ solid concrete floors
In-situ hollow block floors
Pre-cast floors
Steel floors
Composite floors
Timber floors
13. REINFORCED CONCRETE FLOOR SLAB:
FUNCTIONAL REQUIREMENTS
o To support its own weight, ceilings & superimposed loads
o To posses an adequate standard of stability
o To restrict the passage of fire
o To restrict the transmission of sound from one floor to another
o To accommodate services readily
o To provide an acceptable surface finish
o To act as dividing element between floor
o Thermal insulation
o Damp resistance
14. REINFORCED CONCRETE FLOOR SLAB: FACTORS
AFFECTING CHOICE OF FLOORING SYSTEM
o Types of building structure loading
o Span-each type of floors tend to be economic over only a
limited range of span/building
o Degree of fire resistance
o Degree of sound insulation
o Provision of services
o Cost
o Speed of erection
16. REINFORCED CONCRETE GROUND FLOOR
SLAB: SOLID GROUND FLOOR
o Can either be plain or reinforced in-situ concrete
o Plain concrete usually:
Suitable for soil with high bearing capacity
Not suitable for basement (to resist upward pressure of sub-
soil water)
Not suitable for floor carrying heavy loads
o Reinforced concrete usually suitable for:
Soil with low bearing capacity
Uneven bearing capacity
Filled ground (tendency of settlement)
17. REINFORCED CONCRETE GROUND FLOOR
SLAB: SOLID GROUND FLOOR
o Thickness of slab varies according to:
Loading
Bearing capacity of the ground
o Floor levels (levels from ground level) depends on:
Nature of the site (e.g., sloping or wet/low laying)
Types of building (e.g., Surau)
Drainage (e.g., gradient for a drain)
o Damp-proof membrane (DPM) will be required at min. 150mm
above ground level
19. REINFORCED CONCRETE
GROUND FLOOR SLAB:
SUSPENDED GROUND
FLOOR
o Suspended ground floor
slab is usually suitable
for ground with low
bearing capacity
o Construction process
similar to upper floor
o Concrete blinding is
required to provide
even surface & to
prevent water to seep
through quickly
20. REINFORCED CONCRETE UPPER FLOOR
SLAB
o Most common form of upper floor construction especially RC
frame structure
o Give maximum freedom in design on plan & section
o Floor thickness vary according to load & span
o Column grids supports beam, & slab spans either one or two-
way direction
21. REINFORCED
CONCRETE UPPER
FLOOR SLAB: ONE-
WAY SPANNING
o Suitable for:
Small/short span
(4.60m – 5.00m)
Medium to heavy
loads building
Rectangular layout
o Construction:
Supported on two
sides
Main bar will be cast
in in one direction
Distribution bar will be
cast the other way
round
Commonly used in
steel frame building
22. REINFORCED CONCRETE
UPPER FLOOR SLAB: TWO-
WAY SPANNING
o Suitable for :
Larger spans
Heavy loading
Square grids (most
economical); can also be used
for rectangular and square
shape floor
o Supported on four sides
o Reinforcement bars in two
directions (two-way main bar) &
both are main bars
o For rectangular grids, the shorter
span carries a greater load
o Economic due to reduction in slab
thickness
23. REINFORCED CONCRETE UPPER
FLOOR SLAB: TWO-WAY FLAT PLATE
FLOOR
o Floor without beam – resting directly on &
cast monolithically with columns
o Slab/plate reinforced at the bottom in each
direction over the whole of its area
o The effect of up truss stress is high
o Reinforcement:
Both direction at bottom over the whole area
Same as two-way span – both are main bars
Both direction at the top of plate
Reinforcement at the top of column is greater to
support the loads from the floor
24. REINFORCED
CONCRETE
UPPER FLOOR
SLAB: TWO-
WAY FLAT
PLATE FLOOR
oGrid repeats uniformly
oSpacing 5.50 m in each direction
between column
oColumn layout similar throughout the
buildings
oMin 3 bays in each direction + ½
bay cantilevered beyond the
external column
For economic reasons:
oResidential (flat): grid spacing of up
to 4.50m with plate slab 125-
150mm thick
oCommercial (offices): grid spacing of
up to 5.00m with plate slab 200mm
thick
Suitable for light & medium
load buildings:
25. REINFORCED CONCRETE
UPPER FLOOR SLAB: TWO-
WAY FLAT PLATE FLOOR
o Advantages:
Simplification of
formwork
Simple
reinforcement
Reduction in dead
weight as
compared to
beams & slab floor
Standard ceiling
height
Overall reduction
in total height of
building
Savings on the cost
of structure (15-
20%) as compared
to beams & slab
floor
26. REINFORCED
CONCRETE
UPPER FLOOR
SLAB: TWO-
WAY FLAT
SLAB FLOOR
o Similar in construction as in flat
plate but are used for heavier
evenly distributed superimposed
loads
o Suitable for warehouses & others
with heavy imposed loadings &
large imperforate, undivided
areas of floor
o Grid spacing of 6.00-7.50m and
for loadings of 4.5kN/m2 and
over, with slab thickness from 225-
300mm
o Thickness – 225-300mm
o Advantages similar to flat plate
27. REINFORCED CONCRETE
UPPER FLOOR SLAB:
TWO-WAY FLAT SLAB
FLOOR
o To increase resistance to shear
& punching stresses over the
points of support (column), the
heads of the columns are
expanded (mushroom cap)
o Mushroom cap can either be
square or circular depending
on the shape of the column
o In some circumstances, the slab
over the mushroom cap can be
thicken to form what is termed
as drop panel
28. REINFORCED CONCRETE
UPPER FLOOR SLAB:
ONE-WAY RIBBED FLOOR
(T-BEAM)
o T-beams cast monolithically
side by side to forming rib at
600mm c/c
o T-beams size – 90 to 100mm
o Depth of rib & slab thickness
depends on the load & span
o Economical up to 10m span,
if over this may require pre-
stressed rib
o An expensive floor to
construct with normal forms,
instead special forms are
required
o Used for light or medium
load
29. REINFORCED
CONCRETE UPPER
FLOOR SLAB: TWO-
WAY RIBBED FLOOR
o Waffle/honeycomb
o Used for heavier loads or
longer spans where thickness of
solid slab might be excessive
o Suitable for widely spaced
square column grid & floor
that support comparatively
heavy load
o Advantages:
Use less concrete &
reinforcement
It has honeycomb pattern –
attractive features
Reduce the numbers of
columns & beams
Cost saving for foundation
due to less load
Add visual aspect of ceiling
31. o Most exposed element in a building
o The supporting structure & the roof must be well-designed &
constructed
o Main function:
To provide protection from the weather
To enclose space & to protect the space it covers (against
rain, wind and snow)
To protect interior of the building from moisture & excessive
heat loss
An integral part of the structural frame – sustain load
ROOF
32. 1. Strength and stability
o Roof structure – A major factor for consideration in the design
& choice of roof structure are span, materials used & its load
over spans of varying degrees
o The economic consideration of roof structure is to keep its
dead weight to a minimum
o Minimum dead weight becomes critical with wide span
building, as such the structural problem in design is trying to
achieve a low dead & live load ratio
o The solutions are:
Characteristics of materials to be used must be stiff & do
not easily bent
Form & shape of the roof
FUNCTIONAL REQUIREMENTS
33. FUNCTIONAL
REQUIREMENTS (CONT’D)
2. Wind pressure
o Varies
according to
its velocity,
the height of
the building &
the locality of
the building
o Wind exert
pressure &
suction on roof
o Excessive
suction can
cause uplift to
roof (stripped
off)
34. FUNCTIONAL REQUIREMENTS (CONT’D)
3. Weather resistance
o Adequate weather resistance should be provided by the roof
covering
o The nature or type of roof covering will affect the form or
shape & some details of the roof structure
4. Thermal insulation
o Does not affect the design of the roof
o Rarely a factor affecting the choice of the roof type because
normal methods of providing it are generally applicable to all
forms of roof
o Methods used vary & involve the incorporation of flexible or
stiff insulating material in or under the roof cladding or
structure
35. FUNCTIONAL REQUIREMENTS (CONT’D)
5. Fire resistance
o Degree of fire resistance depends upon the proximity of other
buildings & the nature of the building which the roof covers
o Adequate fire resistance is necessary in order to:
Protect against the spread of fire from and to any adjacent
buildings
To prevent early collapse of roof
6. Sound insulation
o Roof construction must provide an adequate degree of
insulation against sound from external sources
o Special precautions in the choice & design of the roof
structure is necessary for buildings like concert hall, cinema
and theatre (in noisy localities)
36. FACTORS AFFECTING THE CHOICE OF
ROOF CONSTRUCTION
1. Type of building
o Either the building is high-rise or low-rise building
o Normally flat roof is used in high-rise building & building of
complex or asymmetrical shape
2. Climate
o Countries with rainy seasons usually have pitch roof to avoid
accumulation of water on top of roof
3. Loading
o Whether the top of roof is intended for transportation area, party,
swimming pool, or services
o Must be able to withstand heavy loads of snow during winter
4. Natural lighting
o Affect the material used in roof
o E.g., stadium needs natural lighting
37. FACTORS AFFECTING THE CHOICE OF
ROOF CONSTRUCTION (CONT’D)
5. Services and piping's
o Usually, flat roof can provide space for air-conditioner unit
6. Speed of construction
o Flat roof takes lesser time to construct
7. Ease of maintenance
o Flat roof is easier to maintain than pitch roof because of the flat
surface
8. Economy
o Flat roof is more economical because less difficulties in construction
9. Aesthetic value
o Pitch roof with coloured tiles is more attractive than flat roof which
has no finishes
10. Prevention of entry of moisture, rain, heat & sound
39. REINFORCED
CONCRETE
FLAT ROOF
o Slope must be not
more than 10°
o Construction details
similar to suspended
floor & gutters are
designed to be hidden
o It can be either solid
reinforced concrete
(half-way span) or pre-
cast
o Unlike suspended floor,
flat roof have
coverings & edge
details
o Less load compared to
suspended floor, hence
no need to use flat
plate
40. REINFORCED CONCRETE FLAT ROOF
o Water proofing can be done by:
Water proofing cement screed
Waterproofed reinforced concrete slab
Add admixture to be waterproof, could eliminate pores in
concrete
No need plaster
Water proofing membrane
o Falls required in flat roof is to encourage natural drain-off of
rainwater to gutter or scupper drain, or rainwater outlet, & falls
can be achieved by using screed
41. REINFORCED CONCRETE FLAT ROOF
o Falls can be classified into:
1-way fall to external gutter
2-way fall to external gutter
4-way fall to external gutter
4-way fall to single internal outlet
4-way fall to multiple internal outlet
4-way fall to 2 outlets & valley
Roof falling to internal gutter
46. REINFORCED CONCRETE FLAT ROOF
o Flat roof finishes:
Material which covers the decking slab to provide protection
from the weather
Finishes also contribute to thermal insulation, resistance to fire
& condensation of the roof
o Finishes can either be:
Single sheet material (metal)
Multiple layer material (bitumen felt)
Monolithic material applied as liquid & dries to form a solid
covering (asphalt)
47. REINFORCED CONCRETE FLAT ROOF
o Monolithic roof finishes:
Mastic asphalt, a mixture of:
Asphaltic cement, which is bitumen (a black water resisting
material which softens when heated and is derived either
naturally or from the distillation of petroleum
Aggregate which either asphalt rock or limestone (limestone
naturally impregnated with bitumen)
Mastic asphalt may be applied to most roof decking
including timber boards & in-situ or pre-cast concrete,
provided that the decking is:
Sufficiently supported to avoid excessive deflection
Laid to fall of at least 1:80
48. REINFORCED CONCRETE FLAT ROOF:
STEPS OF MONOLITHIC ROOF FINISHES
The decking is
covered with
sheathing felt (an
underlay of bitumen
impregnated felt)
Mastic asphalt is
heated & spread over
the sheathing felt by
wood float
The asphalt is applied
in two coats of 10mm
thick
A surface of
protective stone
chippings is applied
on top of the asphalt
52. REINFORCED CONCRETE FLAT ROOF
Advantages Disadvantages
o Simple construction
o Space can be used for
mechanical plant
o For complicated plan shape,
flat roof is the best solution
o Poor insulation against transfer
of heat (no space between roof
and space below)
o Tendency to give an
appearance of unfinished
building
o Ponding of water if not
properly constructed
o Tends to collects leaves, etc.
o Leakage due to failure of
water proofing construction
53. TUTORIAL 4
o A suspended concrete floor is a floor slab where its
perimeter is, or at least two of its opposite edges are,
supported on walls, beams or columns that carry its self-
weight and imposed loads. With the aid of sketches,
explain in detail the construction of suspended concrete
floors.
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