The successful completion of any structural design project is dependent on many variables. However, there are a number of fundamental objectives which must be incorporated in any design philosophy to provide a structure which, throughout its intended lifespan: (i) will possess an acceptable margin of safety against collapse whilst in use (ii) is serviceable and perform its intended purpose whilst in use (iii) is sufficiently robust such that damage to an extent disproportionate to the original cause will not occur (iv) is economic to construct, and (v) is economic to maintain. Historically, structural design was carried out on the basis of intuition, trial and error, and experience which enabled empirical design rules, generally relating to structure/member proportions, to be established. These rules were used to minimise structural failures and consequently introduced a margin-of-safety against collapse. In the latter half of the 19th century the introduction of modern materials and the development of mathematical modelling techniques led to the introduction of a design philosophy which incorporated the concept of a factor-of-safety based on known material strength, e.g. ultimate tensile stress; this is known as permissible stress design. During the 20th century two further design philosophies were developed and are referred to as load factor design and limitstate design; each of the three philosophies is discussed separately in Sections 3.2 to 3.4.
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- Design Philosophies and the Eurocode Program
B.Sc., Ph.D., C.Phys., M.InstP., C.Eng. William M. C. McKenzie
- Macmillan Education UK
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