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Design criteria






STRUCTURAL DESIGN

Warming-up

1. What basic theories of structural design do you know?

2. What types of loading can you name?

3. What scientists worked out the fundamentals of structural design?

Read the text and answer the question: What is required for the safety of the structure?

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 18th 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 estimated by simple proportion. For greater safety, some factor would be allowed on the measured or estimated strengths.

During the 19th 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.

Design

In the first half of the 20lh century, design criteria for particular classes structure — like steel frames and reinforced-concrete frames — were ogressively codified for normal design in terms of design loads.

In the last few decades, far more again has been learned about likely ads, particularly wind loads and earthquake shocks.

Vocabulary

equilibrium — равновесие

obvious — вероятный, очевидный

wagon — тележка, повозка, фургон

masonry pier — каменный столб

tie — растянутый элемент

rod — стержень, прут, брус

specimen — образец

to failure — повредить

to estimate — оценивать

to allow — допускать, разрешать

to bypass — обходить, окружать, окаймлять

reliance — уверенность; опора

frame — остов; каркас

Fill in the gaps with the appropriate participle.

1. The basic theory of static equilibrium for forces... in any direction

was first applied in the second half of the 18th century,
a) acted b) acting

2. For greater safety, some factor would be allowed on the... strengths.

a) measured b) measuring

3. Tests were made to determine both wind loads and the effective loads

imposing by... locomotives.

a) moving b) moved

4.The data obtained remained of... and somewhat questionable
validity.

a) limiting b) limited

Translate this text.


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