Современная архитектура. Гусева О.Г - 32 стр.

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УлГТУ | Ульяновск

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31
b) pentagonal
c) quadrangular
Design Criteria
When the basic theory of static equilibrium for forces acting in any direction was
first applied in structural design in the second half of the 18
lh
century, the criterion of a
safe design seemed obvious enough. The structure would be safe if it could support its own
weight, and perhaps the weight of a wagon passing over it, or of machinery on a floor,
without overloading any crucial element — arch rib, beam, column, masonry pier, or tie
rod. The strength of these elements could be assessed by loading specimens to failure, or
by similarly loading specimens of the material if the strength of the element could then be
estimatedby simple proportion. For greater safety, some factor would be allowed on the
measured or estimated strengths.
During the 19'
h
century, loads other than the weight of the structure itself became
more important. The development of elastic theories of the behavior of the main structural
elements and some complete structural systems called for further criteria to bypass the
reliance on strength tests of these elements and systems. Tests were made to determine
both wind loads and the effective loads imposed by moving locomotives, but the data
obtained remained of limited and somewhat questionable validity for want of adequate
understanding of the nature of these dynamic loads.
In the first half of the 20
th
century, design criteria for particular classes of structure
— like steel frames and reinforced-concrete frames — were progressively codified for
normal design in terms of design loads and allowable stresses.
In the last few decades, far more again has been learned about likely loads,
particularly wind loads and earthquake shocks.
_________________
Vocabulary:
equilibrium
obvious
wagon
masonry pier
tie
rod
specimen
to failure
to estimate
to allow
to bypass
reliance
frame

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