Efficiency of material used:
In multi storey buildings the
panels are either installed as spandrel panels between the columns or they may
take the form of large panels which contain the windows the spendrel panels may
also be supported by the floor slabs the bracing panel may be disposed
horizontally or vertically in the later casting and should be so interconnected
as not to go any relative movement.
replaced by reinforced concrete
wall panels. The external surface of these panels is usually finished like a
last stone facing. This giving them an attractive appearance.
Wall panels are adequate for
resisting wind load which acts 1st to their own plane for bearing
forces acting led to the longitudinal axis of the building. This ensures the
rigidity of the building in the longitudinal direction without using any other
bracing structures.
Wall panels can be made of light
wt concrete reinforced concrete or partly of reinforced and partly light weight
concrete when reinforced concrete is used a heat insultating layer it necessary
is subsequently laid
Wall panels can be divided into
two groups to first belong the panels which transfer their own weight or other
vertical forms by same means to the column or flames. These are called
horizontal wall panels.
The second group involves panels
resting on and borne directly by the footing or footing beams.
These panels don't transfer any vertical forces to the columns or frames
and
are called vertical (slanting)
wall panels. In both groups solid windowed and must be distinguished.
Horizontal (lying) wall panels
having a width of 0.6-2.00 m are self bearing between too adjacent frames and
transfer their load directly to the columns.
A horizontal (lying) wall panel
being a compound of light weight and reinforced concrete is to be seen in fig.
The length of this panel is 5.98 m. The width is 1.18 m to the thickness is
0.2m. The outer surfaces is formed by a 2.5 cm thick reinforced concrete slab
covered with a cast-stone like layer made of crushed limestone. The other parts
of the panel are made of concrete using formed blast furnace slag and aggregate
the quality of this concrete is LC too it also reinforced. The embedded paces
for angles steel for foiling and for hoisting hooks however are made. The total
weight is 33,000 kg the height up to the upper hinges is 41.55 m the gauge of
the rail tracks is 12-14m for the same machine but with columns assembled of 4
sections the data are total weight of 20,000 kg height 20m, track gauge 9m. The
maximum hosting capacity is in both cases 35 tons using two cranes to tons. The
possible deviation of the hoisting by a mortar built into the structure of its
permissible to move it in the unloaded state only. Hoisting is performed by a
27 HP mortar tilting by a 6HP are
The permitted tilting movements
with the load on the crane, performed with motar power, are 50cm in the
longitudinal and 70cm in the traverse direction both to the right and to the
left of the basic position. These movements enable the hoisted member to be
accurately placed.
The
machine is operated by remote consist and must be reliability granded.
The crane is assembled on the
ground with extended columns. Then gripped by the upper bridging part it is
lifted by a 20 tons must crane to a height of about 15M. The wide flung columns
are pulled toward each other by a winch. So bring the crane to a operational
produced.
Wall
panels used in the construction of the Tisza region chemical combine.
may be
constructed by
a) Purlins
with covering of roofing slabs or corrugated asbestos cement sheets
b) Large
roofing units.
Roofing slabs or corrugated asbestos cement sheets
laid on purlins
These are the most popular forms
of roof covering used in central Europe. This is not surprising considering the
simplicity of manufacture of purlins and the availability from stock of factory
made lightweight roofing slab and panels.
The structural system of the purlins may be
a) Freely supported beam b) The cantilever girder
c) The continuous girder.
The connection of the purlins
over the support are designed only to absorb a limited BM. Normal purlins spans
between 5 and 10m. The purlins are spaced at intervals of 2 to 3m.
Purlins:-
Purlins are usually solid web
members. For long spans they may lattice girders or trussed beam.
Freely supported purlins are
designed as let flanged or fish-belly members. Purlins designed as cantilever
grilles (articulated griders) are usually llel flanged members.
The c/s feature depend on the spans
of purlins & on the slope of the roof. The purlins for flat roofs are
usually rectangular T-section or (prestressed concrete) T-Section members for
steeply sloped roofs it the loaded also in biaxial bending L-Sections or
channel sections are used.
Purlins section & the
approximate spans associated with them for a purlins spacing of 3m are
indicated for flat roofs. The dimensions relate to freely supported purlins.
Purlins sections with associated
spans for a purlins spacing of about 1.25 M in the case of steeply sloped roofs
with corrugated professor von Halazz. They are convenient to manufacture with
the legs of the channel upwards. whereby ray thin webs can be produced.
This type of purlins may be
conventionally reinforced or by prestressed. Also they may be freely supported
or be continuous over several spans. In case of L-shaped purlins usually only
the flange of the section is supported.
The fishbelly girder is very
favourable with regard to material requirements & the patterns of forces in
the girder, but it has the disadvantages of being rather unsatisfactory from
the point of view of architectural aesthetics. When it is used generally
designed as a reinforced concrete purlins.
Structural connection to the main beams may be
constructed as follows:-
a) By
supporting the entire c/s of the purlins, the latter being secured to the beam
by means of dowels, projections concreted on to the beam so-called shoes
thickening the top flange of the beam with insist concrete or performed
recesses in the beam.
b) The two
last-mentioned methods are more particularly suitable for purlins of
rectangular section. If the main beam is not provided with recesses to receive
the ends of the purlins, it is desirable to apply an insite concrete topping to
it, else there will be gap between its top flange & the roofing slabs,
which not only looks rather unrightly but also aolds unutilisable, extra space
to the enclosed volume of the buildings on the other hand, when recesses have
to be formed in the top of the beams, concreting presents-difficulties Besides
the recesses weaken the top flange unless it is possible
the supports. Because of this local strengthening
it is possible to reduce the depth of the purlin over the rod beam. There are too
possibilities 1) The end of each purlins is reduced the depth to form a nib
which rests on the beam. 2) The diaphragm on the top flanges of the roof beam
is provided with nibs or corbels for supporting the purlins.
Purlins based on the principles of the cantilever
girder. Provided with hinges which are so located as to ensures statical
determining have not proved satisfactory. The reason for this are a) Halved
joints:- The requirements of careful workmanship are more stringent than are
normally considered acceptable in practice.
By large force will develop, more particularly in
the purlins of long buildings, the failure of one member is liable to result in
the collapse of the whole structure. This has indeed happened in a number of
buildings.
The roofing slabs laid on the purlins of flat
roofs are usually 0.5 TO 1.0m wide & have sparts of about 2.0 to 5.0m these
slabs also comprise the thermal insulation and where necessary, also the cement
mortar screed for the gravel roof.
The wt of slabs varies bet 10 & 150kg/m
depending on the bulk density of the insulating materials and on the span.
a) Ordinary
concrete : 'Waffle' slabs with a shell thickness of only 1cm have been produced
by the firm of press AG. The concrete bad a specified 28 days strength of 600kg
/m2.
b) layer, are
manufactured on vibrating
tables in
Hungary
the output per vibrating table is about 100 slabs per day. The slabs have
standardized
dimensions of 0.5 x 3.0m.
c) Roofing
slabs can be produced in a simple manner from perforated bricks or fixed
insulating clay. The reinforcement is passed through cavities. These slabs are
20cm wide & 8 to 10cm thik for spans upto 2.8 m.
d) I,
perforated bricks or light wt bricks are used in conjunction with reinforced concrete
ribs to form slabs 0.87 m wide & upt 3m span.
e) Pumice
concrete slabs ('Planks') have been produced in germany for a good many gears,
they are available in 3 forms slabs with circular cavities, 'waffle' slabs comprising
longitudinal and transverse ribs, & sold slabs-1.
f) Duris of
roof slabs are used in many countries. The standard slabs are 50cm wide & 2
to 4 long. This concrete is not hygso scopic to that these slabs can also be
used in damp surroundings without suffering any appreciable loss of Thermal
insulating capacity.
g) Hebel
aerated concrete roofing slabs used in Germany and Switzerland are likewise
50cm wide 2 to 6m long. They are reinforced & light wt concrete of with
they are made has a compressive strength of 35 to 50kg/cm2.
Large individual precast units are better able to fulfill the
requirements of industrialized old than purlins & relatively small roofing
slabs can they will therefore gradually suppressed the more conventional form
of construction with roofing slabs & purlins. The advantages are
a. The
number of units is substantially reduced
b. The slab
& web of the unit are concrete as single monolithic whole with structural
co-operation of the slab.
c. Window
bracing for roof are dispensed with as it is readily possible to inter connect
a number of large roof units.
d. Large
roof units generally produce an aesthetically more pleasing result.
The requirements applicable to roof units may be summarized as
follows.
1. The units
should readily lend themselves to type standardization & to quantity
production with the minimum of labour.
2. They
should require the least possible quantities of material both in terms of
concrete & of reinforcing steel.
3. They
should be suitably transportable & capable of being conveniently stacked.
4. When
joined together they should act as rigid diaphragms, so that no other form of
wind bracings needed.
Countries
they are reinforced & the light wt which is aerated concrete.
(k) Hollw prestressed concrete
concrete slabs of the schater system are produced with light wt concrete core d
are suitable for span up to 6.5 m.
Many other types of roofing slabs
are manufactured from a variety of light wt materials.
How
roofing slabs are supported on the purlins.
The standard specifications of
some countries require that roofing slabs be designed as freely supported
members without taking structural continuity into account. However it is normal
practices always to install reinforcing bars in the longitudinal joints not as
a means of establishing true continuity but merely to inter connect and locate
the slab.
Structural continuity can be
achieved by appropriate forms of construction with prince or other light wt
concrete slabs. Tests have confirmed that the failure load is increased as a results
of such arrangements.slabs.
2) Roof units with 3D structural
action such as singly & doubly curved shells & fololed plate
structures.
Hollow
roofing slabs with rectangular cavities.
Slab type
roof units are subdivided according whether they have structural longitudinal
& transverse ribs or only structural longitudinal ribs.
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