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Design of Structures for the
Architecture. STEELS. Steel: Alloy of iron and carbon (this
one last one between 0,5 and 1,5%). What provides qualities of malleability,
hardness and resistance. Of the materials commonly used for structural aims, the
steel is the one that has better properties of resistance, rigidity and
ductility. Its structural efficiency is in addition high because it can make
more in sections with the form adapted to resist the flexion, compression or
another type of requesting. The resistance in compression and tension are
practically identical and can be made vary within a quite ample interval
modifying the chemical composition or by means of work in cold. It is necessary
to take into account that as it is increased the resistance of the steel is
reduced its ductility and that when increasing the resistance does not vary the
modulus of elasticity, reason why become more critical the problems from local
buckling of the sections and global from the elements. For that reason, in the
normal structures the resistance of 2500 steel does not exceed kg/cm2, whereas
for reinforcement of concrete, where buckling problems do not exist, steel of
6000 are used frequently kg/cm2 and for preeffort until of 20000 kg/cm2. The
continuity between the different components from the structure is not so easy to
obtain as in the concrete one reinforced, and the design of the meetings, welded
or screwed at the present time, requires of special well-taken care of so that
they are able to transmit the requesting that its structural operation implies.
Being a material of industrialized and controlled production, the structural
properties of the steel have generally little variability.
Coefficient of variation of the order of 10 percents is
typical for the resistance and the other properties. Another advantage of the
steel is that its behavior is perfectly linear and elastic until the flow, which
more easily makes the answer predictable of the structures of this material. The
high ductility of the material allows redistributing concentrations of efforts.
The extraordinary structural qualities of the steel, and specially their high
resistance in tension, have been taken structurally advantage of in a great
variety elements and composed materials, the first among them concrete one
reinforced and the reinforced one; in addition in combination with wood,
plastics, rubblework and others. The possibility of being attacked by the
corrosion causes that the steel requires protection and certain maintenance in
environmental conditions. The cost and the problems that are originated by this
aspect are sufficiently important so that they incline the balance towards the
reinforced use of concrete in some structures which they must be exposed
outdoors, like bridges and certain marine works, although in steel a slighter
structure and of smaller initial cost could be obtained one more. Types of Steel
and their resistance.
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