3. LIFTS AND ESCALATORS
Lift
The smartness of any vertical system depends upon the
intelligence with which it handles the traffic. The
transportation capacity of any elevator system depends
upon the critical period of maximum demand and the
system must serve the calls during the period of
maximum demand while simultaneously subjecting
passengers to an acceptable waiting period of time.
The no. of elevators and the locations in a particular
building depends upon various factors like flow of traffic,
building population, quality and quantity of services
expected.
Hc = 300p/t ---hc-handling capacity of car, t—round trip
time, per persons/car.
N=vi/300p=v/hc,v—peak hr. traffic
Lift/elevator an appliance by which persons and goods
are moved vertically from one level to another; its
component part consists of the winding machine, car,
counterweight, guides, suspension ropes, control gear
with safety devices.
4. LIFTS AND ESCALATORS
Passenger elevator
Structural slab of machinery, 150 mm thk. Designed to sustain
min. 1000kg/m2udl.
Power supply 400volts, 3phase,4wires & 230 volts 1phase.
All hoist way walls should be minimum 230mm brick or
150mm r.c.c.
Centre opening door should be preferred.
Depth should be 1.40m (4’6”) below the lowest landing lvl.
Lift pit on hard strata---raft foundation-completely water tight,
m.s. Ladder to be provided
Provide 40cmx40cmx75cm,1:2:4 concrete blocks in lift pit
for buffer spring.
Rcc bracer beams to be provided in bk. Masonry & guide
rails should be fixed to it.
4 no. Pockets to be provided in machine room slab as fixing
supports.
Specifications to be confirmed with elevator agency.
5. LIFTS AND ESCALATORS
Grouping of elevators----minimize
walking distance between entrances,
quick access to cars, less confusion
between waiting passengers.
6. Escalator
An escalator is a conveyor transport device for transporting people, consisting of individual, linked steps
that move up or down on tracks, which keep the treads horizontal.
As a power-driven, continuous moving stairway designed to transport passengers up and down vertical
distances, escalators are used around the world to move pedestrian traffic in places where elevators
would be impractical. Principal areas of usage include department stores, shopping malls, airports, transit
systems, convention centers, hotels, and public buildings.
The benefits of escalators are many. They have the capacity to move large
numbers of people, and they can be placed in the same physical space as
one might install a staircase. They have no waiting interval (except during
very heavy traffic), they can be used to guide people toward main exits or
special exhibits, and they may be weatherproofed for outdoor use.
Electric traction elevators are used in exclusively in tall buildings.
Hydraulic elevators are used generally in low rise freight service which
rises up to about six storey’s & also for low rise passenger service.
Escalator’s to be viewed as preferred transportation system whenever
heavy traffic volumes are expected between relatively few floors.—
AIRPORT TERMINALS, SHOPPING malls, etc.
Escalators used when it is necessary to move large no. Of people from
floor to floor.
7. These stairs have continuous operation without the need for operators.
Minimum depth of tread-indirection of travel –400mm
Maximum rise between treads –230mm
Minimum width of tread -- 600mm
Maximum width of tread –1000mm
Maximum clearance bet. Tread & adjacent skirt
panel Maximum distance bet. Handrail centrelines—758mm(min)
Width of escalator---1140mm
Steps
Hand Rail
Truss
Driving Machine
Endless Belt
9. A shell structure is a thin, curved membrane of slab, usually of reinforced concrete, that functions both as
structure and covering, the structure deriving its strength and rigidity from the curved shell form.
It is generally capable of transmitting load in more than two directions to supports. These
structures are highly efficient structurally when they are so shaped, proportioned and supported that they
transmit the loads without bending or twisting. A shell is defined by its middle surface halfway between it’s
inner surface and outer surface. Depending upon the geometry of the middle surface, shells may be
classified as:
•A Dome
•A barrel arch
•Cone, and
•Hyperbolic and parabolic
A thin shell has relatively small shell compared to other dimensions. It should not be so thin that
the deformation would be large compared with the thickness. The shell shearing stresses normal to the
middle surface should be negligible. The thin shells usually are design so that normal shears, bending
moments and torsions are very small except for relatively small portions.
The term shell is used to describe these structures by reference to the very considerable strength
and rigidity of thin, natural, curved forms such as the shell of an egg, a nut and crustaceans such as the
tortoise. The strength and rigidity of curved shell structure makes it possible to construct single curved
barrel vaults 60 mm thick and double curved hyperbolic paraboloids 40 mm thick in reinforced concrete for
spans of 30.0.
SHELL STRUCTURES
SHELLS
10. Single curvature shells, curved on one linear axis, are part of a cylinder or cone in the form of barrel
vaults and conoid shells. Double curvature shells are either part of as sphere, as a dome, or a
hyperboloid.
The term single curvature and double curvature are used to differentiate the comparative
rigidity of the two forms and the complexity of the centering necessary to construct the shells forms.
Double curvature of a shell adds considerably to its stiffness, resistance to deformation under load and
reduction in the need for restrain against deformation.
The most straightforward shell construction is the barrel vault, which is part of a cylinder or
barrel with the same curvature along its length. The short span barrel vault is used for the width of the
arch ribs between which the barrel vaults span. It is cast on similar arch ribs supporting straight timber or
metal centering which is comparatively simple and economic to erect and which can, without waste be
taken down and use again for similar vaults.
A shell structure is many times more expensive than a portal frame structure covering the
same floor area because of the considerable labor require to construct the centering on which the shell
is cast.
The material most suited to the construction of a shell structure is concrete which is a highly a
plastic material when first mixed with water that can take up any shape on centering or insert formwork.
SHELLS
12. Domes
Domes are semi-spherical or semi-elliptical in shape. They are
used as roof structures. Constructed of stone or bricks or concretes. They
are supported on circular or regular polygon shaped walls.
Dome structures have within certain height and diameters vary
small thickness. Dome structures are generally used in monumental
works were roof are to be build on building circular or hexagonal in plan.
The domes can be either
(1) Smooth shaped domes
(2) Ribbed domes.
Smooth shell domes can have either shell of uniform thickness or
with shell of uniformly varying thickness. A dome can be constructed with
or without lantern.
Space frame dome exceptionally light structures, which permit
the spanning of large distances with relative reduction materials. The
dome surface can be subdivided into a number of triangles or other
regular polygons the sides of which are hinge bars.
Any dome shell roof will tend to flatten due to the loading and this
tendency must be resisted by stiffening beams or similar to all the cut
edges. As a general grid domes which rise in access of 1- 6 of their
diameter required a ring beam. Timber domes like their steel counter parts
are usually constructed in a single layer grid system and covered with a
suitable thin skin membrane.
SHELLS
13. Conoid Shells
These are similar to barrel vaults
but are double curvature shells
as opposed to the
singlecurvature of the barrel
vaults. Two basic geometrical
forms are encountered.
A straight line is moved along a
curved line at one end and a
straight line at the other end. The
resultant shape being cut to the
required length.
A straight line will move along the
curve line at one end and the
different curve line at the other
end.
SHELLS
14. Barrel Vaults
These are shells of single curvature and are commonly called barrel vault. Geometrically a
barrel wall is a cut half cylinder which presents no particular setting out problems. When two barrel walls
intersect the lines, lines of intersection are called groins. Barrel walls like domes tend to flatten unless
adequately restrained and in vault restraint will be required art the ends in the form of a diaphragm and
along the edges.
From a design point of view barrel vaults act as a beam with the length being considered as the
span which if it is longer than its width or chord distance is called a long span barrel vault, or conversely if
the span is shorter than the cord distance is termed short barrel vault.
Short barrel vaults with their relatively large chord distance and
consequently large radii to their inner and outer curved surfaces may
require stiffening ribs to overcome the tendency to buckle. The extra
stresses caused by the introduction this stiffener or ribs will necessitate
the inclusion of extra reinforcement at the rib position, alternatively the
shell could be thicken locally about the rib for the distance of about 1/5th
of the rib spacing.
The concrete shell is from 55-75 thickness for
span of 12.0-30.0 respectively. This thickness of concrete provides
sufficient cover of concrete to protect the reinforcement against damage
by fire and protection against corrosion. The wet concrete is spread over
the centering on the reinforcement and compacted by, hand to the
required thickness.
SHELLS
15. The usual form of barrel vaults is the span
vault where the strength and stiffness of
shell lines at right angles to the curvature
so that the span is longitudinal to the
curvature. The usual span of a long-span
barrel vault is from 12.0-30.0 mts. with the
width being about half the span and the
rise about one fifth of the width. To cover
large areas, multi-span, multi-bay barrel
vault roofs can be used where the roof is
extended across the width of the vaults as
a multi-bay roof, as a multi-bay, multi-span
roof.
Edge and valley beam
Due to the self-weight and imposed loads the thin shell
will tend to spread and its curvature flatten out. To resist this,
reinforced concrete edge beams are cast between columns as
an integral part of the shell. Edge beam may be cast as a drop
beam or upstand beam or partly dropped beams.
SHELLS
16. Expansion joints
If there is excessive contraction or
expansion the stresses so caused
might deform the shell and cause
gradual collapse. To limit contraction
or expansion, continuous expansion
is formed at interval of about 30
mts. Both along the span and
across width of multi bay, multi span
barrel vault roofs. The expansion
joint transverse to the span of the
vaults is formed with a non-ferrous
flashing to weather. Longitudinal
expansion joints are formed in a
valley with upstand weathered with
non-ferrous capping over the joint.
SHELLS
17. North light reinforced concrete
barrel vault
To avoid the possibility of
overheating and glare from top light
in the summer a system of north light
reinforced concrete barrel vault is
used. The roof consist of a thin
reinforced concrete shell on the
south facing side of the roof with a
reinforced concrete framed north
facing slope, pitched at 60-80
degree.
Rigidity of barrel vault depends on its
continuous curvature, which in this
type of roof is interrupted by north
light opening. North light shell is less
efficient structurally than a barrel
vault shell. The economic span of the
north light shell is 12 – 15 Mts. as
compared to 30 or more of barrel
vault.
SHELLS
19. Hyperbolic Paraboloids
These are obtained by sliding a vertical parabola with upward
curvature on another parabola with downward curvature in a plane at
right angle to the plane the first. Here directions, up in one and down in
the other. This surface generally called a saddle surface. There are
different ways in which saddle surfaces can be supported. The surfaces
are generally design with small rises so as to produce fairly flat roofs. If
cut by planes parallel to the two parabolas, the edges will be parabolic
and the supporting structure must be parabolic.
To obtain a more practical shaped than the true saddle
the usual shaped hyperbolic paraboloid which is formed by rising of or
lowering one or more corners of a square. By virtue of its shape this form
of shell roof has a greater resistant to buckling than dome shapes.
Hyperbolic paraboloid shells can be used singly or conjunction with one
another to cover any particular plan shape or size. If the rise is small the
result will be the hyperbolic paraboloid of low curvature acting structurally
like a plate which will have to be relatively thick to provide the necessary
resistance to deflection. To obtain full advantage of the inbuilt strength of
the shape the rise to diagonal span ratio should not be less than 1:15
indeed the higher the rise the greater will be the strength and the shell
can be thinner.
SHELLS
21. SPACEFRAME
A space frame or space structure is a truss-like, lightweight rigid
structure constructed from interlocking struts in a geometric pattern.
Space frames usually utilize a multidirectional span, and are often used
to accomplish long spans with few supports. They derive their strength
from the inherent rigidity of the triangular frame;
flexing loads (bending moments) are transmitted
as tension and compression loads along the length of each strut.
Most often their geometry is based on platonic solids. The simplest form
is a horizontal slab of interlocking square pyramids built from
aluminium or tubular steel struts. In many ways this looks like the
horizontal jib of a tower crane repeated many times to make it wider. A
stronger purer form is composed of interlocking tetrahedral pyramids in
which all the struts have unit length. More technically this is referred to
as an isotropic vector matrix or in a single unit width an octet truss.
More complex variations change the lengths of the struts to curve the
overall structure or may incorporate other geometrical shapes.
Space frames were independently developed by Alexander Graham
Bell around 1900 and Buckminster Fuller in the 1950s. Bell's interest
was primarily in using them to make rigid frames for nautical and
aeronautical engineering although few if any were realised. Buckminster
Fuller's focus was architectural structures and has had more lasting
influence.
SPACEFRAME
Space frames are an increasingly common architectural technique especially for large roof spans
in modernist commercial and industrial buildings.
22. ADVANTAGES OF SPACE-FRAMES:
Space frame systems are three-dimensional structures which are constructed by connecting straight
tubular struts to each others with the use of solid spherical hubs. Theese systems carry loads by axial
forces. The conic parts are welded to the strut edges and the struts connecting by spherical hubs.
Some of the advantages of space frames are described below:
•Because of the space frame systems are three-dimensional structures which work in two direction, for a
large spans it provides economical solutions.
•İt is possible to cover spans until 100 m. without column by using space frame systems.
•They provide a great flexibility in the selection of support locations and allows to apply for different
geometrical shapes / areas.
•The design / manufacture / installation process is completed in a very short interval due to the use of
prefabricated components. İt gives a big opportunity to the customer to start his production
•Transporting to far distances is provided easily due to the use of prefabricated components.
•Space frame systems are lighter than traditional steel and reinforced concrete structures. Therefore, it
provides significant economy in foundation costs.
•Space frame systems are the most useful structures for the earth-quake areas due to their light unit
weight.
•İt is not nacessary to cover by hung ceilings because of its aesthetic appearance.
•Additional structures to support the heating, ventilating, electrical and other systems are not required for
space frame structures.
•Because of the aesthetic attribute, space frames are very suitable for glass or policarbonate skylights.
•İt provides various alternative solutions in architectural areas for complex geometrical shapes (pyramid,
triangle, dome, barrel vault e.t.c.)
SPACEFRAME