SUSPENDED FLOORS : concrete

lifegunbarrelcityΠολεοδομικά Έργα

26 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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posttensioning:

-

performed on site

-

tension the steel tendons after the concrete is cast


SUSPENDED FLOORS : concrete

CONSTRUCTION AND DETAILING 1

precast concrete systems:



-

precast slabs, beams, tees, one
-
way spanning units


-

cast and cured in a factory / plant


-

transported as components to site


-

set in place on site


-
prestressed for greater structural efficiency


-

supported by


-

walls: insitu concrete / precast concrete / masonry loadbearing


-

frames: steel / insitu concrete / precast concrete


SUSPENDED FLOORS : concrete

CONSTRUCTION AND DETAILING 1

-

advantages


-

less depth


-

reduced weight


-

longer spans


-

disadvantages


-

modular nature not suitable for irregular building shapes


-

generally standard sizes


-

all service opening must be predetermined


-

cannot chase or core into slab



(unless first analysed by engineer although still risky)



SUSPENDED FLOORS : concrete

CONSTRUCTION AND DETAILING 1

hollow core slabs:

-

one
-
way spanning units

-
placed on in
-
situ or precast concrete beams /


steel beams / masonry

-
cast in the factory with

-
smooth finish for painting or floor finish

-
delivered so site

-
positioned with cranes



SUSPENDED FLOORS : concrete

CONSTRUCTION AND DETAILING 1

-
precast ribs with infill blocks:


-

ribs with blocks are one
-
way spanning units


-

supported on



-

in
-
situ or precast concrete beams



-

steel beams



-

masonry walls


-

infill blocks



-

made of concrete or clay



-

hollow or solid


-

cast in the factory


-

delivered to site



-

positioned without cranes


-

reinforced concrete topping cast over



-

forms part of the structure



SUSPENDED FLOORS : concrete

CONSTRUCTION AND DETAILING 1

CONSTRUCTION AND DETAILING 1

steel

-

steel beams or joists to support


-

metal decking


-

precast concrete slabs


-

light
-
gauge steel joists


-

light, stable, span long distances


-

easily assembled


-

lightweight, non
-
combustible



floor structure


-

laid out at certain spacings



-

depending on loads of floor


-

spans:



-

150x40mm between 3m


4,2m



-

300x65mm between 5.4m


8m


-

covered with



-

rc concrete over metal decking



-

timber subflooring


SUSPENDED FLOORS : steel

CONSTRUCTION AND DETAILING 1

-

metal decking


-

corrugated


-

increase stiffness and spanning


-

acts as formwork for insitu concrete slab


-

decking panels secured with studs



-

welded or rivetted through to the beams


-

panels fastened to each other with screws / welds / seams



-

types



-


steel beam decking



-

open web steel joist decking











-

types of steel beam decking:








-

form decking








-

composite decking








-

cellular decking


SUSPENDED FLOORS : steel

CONSTRUCTION AND DETAILING 1

form decking:

-

permanent formwork


-

for reinforced concrete slab


-

until slab can support itself and live load



composite decking:

-

tensile reinforcement for concrete slab


-

bonded to it with embossed rib patterns

-

composite action achieved


-

between slab and beams


-

welding shear studs through decking



onto beam below



cellular decking:

-

welding corrugated sheet to flat sheet

-

series of concealed spaces formed for


-

electrical and communication services through floor outlets


-

acoustic ceiling when filled with glass fibre


SUSPENDED FLOORS : steel

CONSTRUCTION AND DETAILING 1

open
-
web joist framing:


-
floor deck may span across joists


(spacing dependent on floor load)


-

floor deck comprised of


-

metal decking with concrete fill


-

precast concrete panels


-

plywood panels / timber planking


-

horizontal bridging


-

prevent lateral movement of joist chords


-

spaced between 3m


6m


SUSPENDED FLOORS : steel

CONSTRUCTION AND DETAILING 1

CONSTRUCTION AND DETAILING 1

timber

-

joists / beams to support


-

planking / decking


-

subflooring


-

joists / beams supported by


-

posts


-

loadbearing walls



-

wood joist floors


-

form a level platform with wood panel sheathing or sub
-
flooring


-

combustible: rely on flooring and ceiling for fire resistance


-

susceptible to decay and insects: drainage and ventilation


-

may be exposed (without ceiling) or concealed (with ceiling)


-

if exposed



-

susceptible to sound transmission



-

lacks concealed space for insulation, service reticulation




SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1


-

joists

supported by


-

wood stud framing


-

wood or steel beams


-

loadbearing masonry


-

concrete wall


-
lateral support for joist ends


-

rim joist or header

-

additional support


-

double end joists


-

stiffness of joist framing is more important than its strength

-
deeper joists spread further apart better stiffness THAN



shallower joists closer together


-
spans dependent on loads, joist size, type of timber

-
depth: span/16 (rule of thumb)


SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1

-

spacing: approx. 400mm centres

-

spacing cavities for piping, services, insulation









-

sizes and span ranges: approx. 3


5m


-

150x50mm up to 3m


-

200x50mm between 2.4m


3.6m


-

250x50mm between 3m


4.2m


-

300x50mm between 3.6m


5.4m








SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1










-

finish to floor structure


-

floor finish applied over timber plank sub
-
flooring




-

underside may be left exposed


-

ceiling applied directly to joist or suspended below




SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1

-

types:


-

subflooring


-

decking



timber subflooring:

-

closely spaced joists with timber panel subflooring over

-

joists


-

openings or cuts may be made for services


-

supported on load
-
bearing walls


-

wrapped in dpm, built into the corbelled brickwork wall


-

fixed to steel brackets bolted onto concrete walls


-

bridging between joists



-

stiffen the floor construction



-

metal or timber cross bracing OR



-

full depth blocking at 2.4m intervals



-

omitted if joist ends are supported laterally against rotation and



edges restrained by subflooring


SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1


-

subflooring


-

material that spans across floor joists


-

working platform during construction


-

provides a base for finish flooring


-

typically plywood


-

underlay and screeds



-

impact (load) resistance



-

sound insulation



-

smooth surface




for flooring material



decking:

-

types:


-

timber planking


-

plywood


-

stressed
-
skin panels


SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1

timber planking:


-

timber planks laid across spaced joists


-

laid perpendicular to joists / beams


-

solid or laminated strip flooring


plywood:


-

laid perpendicular to joists / beams


-

30mm thick over 1.2m span


-

laid continuously over 2 spans


-

tongue and groove edges



stressed
-
skin panels:

-

plywood facing bonded to distribute loads


-

with adhesive


-

to solid timber stringers and cross bracings

-

integrated into single component with:


-

thermal insulation
,
vapour retarder
,
interior finish


SUSPENDED FLOORS : timber

CONSTRUCTION AND DETAILING 1


1.
Ching, F.D.K (2008)

Building Construction Illustrated 4
th

edition
, John Wiley & Sons:
New York.

Chapter 4: Floor Systems

Chapter 5: Wall Systems


2.
Grobbelaar, A (2010)

Building Construction & Graphic Standards
, Anglo
-
Rand
Publications: South Africa.





SUSPENDED FLOORS : sources

CONSTRUCTION AND DETAILING 1