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Construction of elevators. An elevator or elevator is an
apparatus that serves to transfer people or things (in which case freight
elevator is called) from floors to others. They are possible to be classified
according to the traction in electrical and oleodinámics. Electrical elevator.
It consists of a cabin that slides by guides, hung by cables of a superior and
balanced pulley with a counterbalance. One moves with an electrical motor. The
Norm imposes that the size of the cabin will be so that more people do not fit
in her of those whose weight is able to move. Oleodinámic elevator. In this case
the cabin moves by means of a system by telescope that extends by means of
introduced oil to pressure by a pump. He is safer than electrodynamic, but the
slowest one and consumes the energy double.
Structures. Structures of Pure Traction: It is the tension state in which the
particles of the material tend to separate. Its cause can be explained like two
forces of equal magnitude but of opposite sense acting on the same straight line
of action. Structures of Pure Traction: We called structures of pure traction to
all to those structural systems that act by their form and are exclusively asked
for internal requesting of traction. We denominated traction to the effort that
makes fibers of a structural element in which its "stretching" takes place
because of which their molecules separate of others. That is that these
structures do not resist another type of requesting but that the one of traction
is not put under nor the compression, flexion, cuts or torsion. The
characteristic deformation is the extension in the direction of the load and
shortening in the other two dimensions. Materials for its construction: The apt
materials to materialize a traction structure are characterized by their GREAT
FLEXIBILITY, that is small moment of cross-sectional inertia, very ELEVATED
LITTLE TENSILE STRENGHT and, that is elevated I modulate of elasticity "E". All
these characteristics are those that cause that a structure works well to the
traction, without as much having deformations in the materiality as in the
functionality. By its form. The elements can be classified in: LINEAR: They are
threads that have little section and great length, for example: wires twisted
cord, wires of parallel wires, cylindrical rod, chain, etc.
SUPERFICIAL: They
are elements of despicable thickness and great surface, for example woven of
wire, plates the important characteristic is the adaptability of the elements
that constitute these structures, that, when receiving the loads acquire a
balance form automatically to funicular. The used materials but are: Steel: it
resists equal or but that other materials in a small section but what space
saves, has liviandad appearance, is of fast installation. Aluminum: it is of
easy work, it has good conductibility, he is resistant to the corrosion, it is a
material light, and deformable olígons Funiculars: The polygons funiculars are
the natural forms to support tensile stress. As it increases I number of loads,
the polygon to funicular taking I number flood of sides but small and it is come
near to 1 curve. It is possible to be said that to an amount "m" of loads
applied to a cable, the polygon to funicular will have m+1 sides. By the loads
on watch in a Structure of pure traction it is defined a polygon to funicular of
x amount of sides. When it increases those sides is defined a curve or one at
least comes near her. The CATENARY is the form of balance (polygon to funicular
of x sides) of a load distributed throughout a thread, of a curve. We can speak
of the load of its own weight in all the cable. Example: a chain; the weight of
its links marks to a catenary the PARABOLA to make it simpler we took the case
from a bridge where the loads uniformity are distributed horizontally. That is
to say, it is the form of balance of a load uniformly distributed throughout a
straight line. |
